Imperial Home Page -> Repair -> Electrical System ->Coil and Ballast Resistor
Purpose of Ballast Resistors from Brooks:
When the engine is running, you can get by fine with a lot less current at the points. That's the purpose of the ballast resistor. If the points were to receive full battery current/voltage at all times, they would only last a few hundred miles before needing replacement.
At the time of cranking (when the starter is operating), a separate wire gives the points the full 12 volts, bypassing the ballast resistor. When you release the key from "start" to "on", all the power to the points now has to flow thru the ballast resistor, preserving the points.
So that's its purpose....for those curious. And I know I'm kinda mixing volts/amps in the above....which isn't fair....but you get the idea.
Addition from Bob:
Let's be clear that there is no separate wire on the early models. The points get the current directly through the ballast. In order to provide the full 12 volts during a cold start, the ballast is also cold and has nil resistance. As the ballast heats up (some of them get VERY hot!) the resistance gradually climbs up to 1.5 th 1.9 ohms thus reducing current to the points.
Doesn't it also reduce the volts to the coil?
Reply from Bob:
Yes it does. After it is warmed up, there should be only 7-8 volts at the coil.
Question from Norm:
One of my favorite car magazines (Car Crafter) had a recent article in which they offered ways to improve performance without spending bucks. For many reasons this is of great interest to me, and perhaps to others as well. CC says to create a hotter spark (and better combustion), bypass the ballast resistor in the ignition circuit. My question is this: Will this create any other problems ? And if not, what's the best way to do this? Or.....should I just buy a hotter coil? And if I do buy a hotter coil, should I modify the ballast resistor?
For the .002 second performance gain, it's not worth running your coil at 12+ volts when it's designed for 9v. You wont wreck it right away, but you will shorten it's life. Something else, the coil will only produce as much spark as the engine "demands". Example, higher engine speeds with their increased combustion turbulence require more voltage than a simple idle. The coil re-acts accordingly. Only an engine capable of... Spinning to higher RPMS (valve springs, cam, etc.) Spinning to high RPM faster (lightened reciprocating engine components) Drawing in more air (cam, heads) ...will notice gains from a higher output coil.
Follow-up from Jack:
Hate to disagree with you, but an ignition coil does not produce a 'hotter' spark as demands such as higher rpm or increased cylinder pressure are placed on the system. The output voltage of the coil will actually drop as rpm increases past 4500. This is a result of the shorter amount of time the primary circuit has to build the required magnetic field. At around 6000 rpm (3000 rpm distributor speed) a conventional breaker point or electronic ignition is just about done. Hence the development of the CD ignition. A magneto, being a small generator in itself, will provide a voltage increase as rpm's rise. A high output coil (25K+ volts) will give you easier starting, better drivability and increased overall performance provided the rest of the system is up to the task. If only someone made a GM HEI conversion for Chryslers. We do agree that by-passing the resistor will destroy the coil in short order.
Reply from Carmine:
Perhaps I should have phrased this differently. Of course the coil doesn't react to engine demands, they have no ability to "sense" a need for higher voltage. I should have said "coil voltage COINCIDES with engine demands". However, I stand by these points...
It's harder to ignite a high RPM air/fuel mix because:
A. Higher RPMs create more cylinder turbulence. A weak flame front can actually be "blown-out" by this turbulence.
B. High RPM air/fuel mixtures are harder to ignite because less time between power-strokes mean less time to re-load the cylinder with fresh air/fuel mix AND less time to evacuate the burned air/fuel mix.
Luckily for the internal combustion engine, ignition coil voltage INCREASES when: Magnetic flux lines move more rapidly--Faster collapse of the magnetic field caused by an abrupt end to current flow. (Higher engine RPMs mean that either breaker points open/close faster (points) or a hall effect switch opens/closes faster (electronic). Thus ignition coils produce more voltage at higher RPMs. An engine "scope" will bear this out.
> The output voltage of the coil will actually drop as rpm increases past 4500. This is a result of the shorter amount of >time the primary circuit has to build the required magnetic field.
This is the point of diminishing returns. Obviously, you'll hit a point where the collapse of the magnetic fields occurs so fast as to decrease voltage.
> At around 6000 rpm (3000 rpm distributor speed) a conventional breaker point or electronic ignition is just about done. >As is your big-block Imperial engine! A high output coil (25K+ volts) will give you easier starting, better drivability and >increased overall performance provided the rest of the system is up to the task.
While I agree with this in "the real world", I disagree in principal. First of all, even a 30-year-old coil can deliver 25KV. The newest Constant Discharge ignition coil-packs can do over 50KV. Second, an electric spark can jump the typical sparkplug gap at less than 5KV. So, all other conditions being ideal, a fuel mix that ignites at 5KV from a CDI system is no better than one ignited at 5KV by a points system. Any coil will stop charging as soon as the spark "jumps". As components age, spark gaps increase, air/fuel mixes are less than ideal, cylinder pressures are higher, the CDI system will show its advantage.
I consider a high output coil a waste for the typical, stock Imperial engine because...
1. Because of their reciprocating mass, intake systems, valve train limitations, they'll never see 5500+RPM (for very long)!
2. An engine kept in good tune (carb, plugs, wires, timing, etc.) will never require more than 25KV to ignite the air/fuel mix. Only when the engine has been modified in some manner (reciprocating mass lightened, valve train improved, induction/exhaust system improved) will the benefits of the higher RESERVE CAPACITY offered by a HP coil be realized.
> We do agree that by-passing the resistor will destroy the coil in short order.
Actually, if somebody wanted to bypass the ballast resistor for a very short period, they could do so without harm. As a science project, you could run your Imperial this way for a few full-throttle runs and see if it makes a difference. Just be sure to re-install the ballast when you're done. I've connected the two ballast connections together for short periods when ballast resistors have failed. Running it like this for a short time won't kill anything.
If you bypass the ballast resistor in a pre electronic ignition car, you will most likely have burned points. The resistor is current limiting as well as voltage dropping and part of its function is to protect the points
Question from Philippe (1957):
I ask myself some questions about the ignition coil location: on all old Mopars the ignition coil sat atop the intake manifold; this location is not perhaps the best for the life of the coil: there's a lot of heat transferred to the coil and I have some friends who had ignition problems because the coil was (or became) bad. When I bought my '57, the coil was mounted on the fender well, beside the washer bag. Because I wanted an original engine bay, I put the (new) coil in its original location but I wonder if I did the best thing? Are today's coils heat-resistant? Perhaps a little heat shield under the coil?
Reply from Dick:
Coils have lived happily on intake manifolds for millions of miles, I don't think you need to worry about it on that account.
However, since you have aftermarket ignition components, I'd carry spares for all of those, or better yet, carry the original system with you, just in case. I trust Chrysler's engineers to properly check out parts in their environment, the aftermarket vendors don't have the resources to do as good a job.
Question from Zan (1962):
My Imperial is giving me fits and not running again. Symptoms: I can start it and drive it for a few minutes until it starts losing power. First it show in acceleration, it will hesitate when I give it gas. Then a minute or so later it loses all power and eventually stalls out. If it rest for a while it will go again w/ same problems. Now it is beached in Crescent Hill sort of close to home but not to near my new mechanic. Equipment that is fairly new that I'll hesitate to question: Alternator, battery*, voltage regulator >Fuel Pump, Radiator** Cap, rotor, condenser, spark plug wires and all wires from condenser to starter *This battery although brand new was subjected to overcharging last weekend when my volt. regulator was out. I'm not totally going to exonerate that piece of equip. **When I had the radiator re-cored my mechanic suggested I might need to >have my thermostat replaced which I never did. Could this be it? I'm trying to be as clear as possible here, noting how nothing should be >assumed to work that I haven't told you about replacing recently. I bought this car 6 months ago with 94K miles, and besides brake work, I'd had the above done with fair confidence that the parts replaced now give me no trouble and I had a reliable performance from them. Finally, I still have not cleaned out my carburetor which runs slightly rough, but not too bad. I'd see this is due, but not the problem.
I had a situation like that with a 63 imperial. It turned to be a bad ignition coil. I would also check your timing and vacuum line to distributor. Also, the wire from wiring harness to + side of coil insulation is probably cracked (38 years of under-hood heat) and wire could be periodically grounding out - causing intermittent ignition failure-everyone should check theirs and at least put a little electrical tape on this wire if cracked- (NOT UNCOMMON).
Your problem could be either a restricted fuel line or a faulty ignition coil. Your description leads me to believe it is the ignition coil. One coil failure mode is to stop working when they heat up and restore themselves to a working condition again when they cool off. If it is fuel line restriction, such as plugged filters, rust in the tank filter, or a defective rubber hose, (or even a non vented fuel cap) it is likely that you will lose power gradually as the carburetor bowl runs dry from lack of fuel. However, nearly always when there is not a 100 percent plugged line there will be enough fuel to idle and the car will continue to run at low speed and low load. I would replace the ignition coil and try it out again. This may not be the cheapest but it is probably the easiest. If this fails go to the fuel filters, or blow out the line between the fuel pump and the tank. (remove the gas cap when you do this to avoid rupturing the tank).
Another idea: if your car is puffing black smoke as it is dieing, maybe the choke is shutting and drowning your motor. Usually the cause is someone has over-tightened the air cleaner wing nut and distorted the upper flange of the carburetor, but for whatever reason, there is a good chance that your choke is sticking closed. Next time you try it, when the car dies, take the air cleaner off and see if you hear a clunk as the choke opens, or maybe the choke is still stuck shut even after you drive the car far enough that it should be opening up (just a block should begin to open it). The choke is the front upper flat plate that goes across the air opening of the top of the front section of the carburetor, and it should be free to flop loosely with only a mild spring tension to position it, (someone has to hold the accelerator down to release the fast idle cam while you check this).
Sounds like you have a fuel delivery problem. I bet your fuel pump is about ready to fail, or you have a blockage somewhere "down the line", or in the carburetor. The symptoms you describe are classic for fuel starvation. If you have a fuel restriction (not a full blockage) idling may be fine, but fuel supply will not keep up with demands from the carburetor under acceleration and moderate open throttle cruising (like on the freeway). Check your fuel filters for gunk/junk. When the car dies, pop the hood and check you fuel filter. Is it empty/dry? Remove the gas cap. Disconnect the fuel line at the fuel pump (between the pump and the tank), connect a long piece of fuel line to the open end and try to blow some air backward toward the fuel tank. Your should hear bubbles. If you can't blow air through the line, you've got some blockage in the lines. (I've never had a blockage that I couldn't clear with a deep strong breath, so I don't know that the best method it to clear the lines. I'm sure other members will have good ideas here) If no blockage, reconnect the fuel pump and start the car, letting it run enough to get fuel back up into the lines, pump and carburetor. Now disconnect the fuel line right ahead of the fuel filter. Connect your long piece of fuel line to the output side of the fuel pump. Get a coffee can or other "catch can" suitable for gasoline, and some eye protection. Hold the end of the fuel line in the coffee can while a helper starts the engine and lets it idle for a few seconds. When the engine starts, you should get gas rushing into the can after a second (no more than two seconds). Be careful, as the gas may come blasting into the can (eye protection, arms length, and keep the can low in the engine compartment to avoid splash on your paint, etc.). If you can blow bubbles, get gas rushing from the pump, and your filter is okay, your problem is a blockage in the carburetor. Time to pull that carburetor, remove the top, and blast it clean with carburetor cleaner. BTW- My experience with fuel pump failure taught me to always carry a spare fuel pump in the trunk. When she (the pump) finally fails (which will eventually happen if she has a corroding gasoline tank) there will be nothing you can do to get her running. Having extra belts, hoses and a fuel pump in the trunk can turn a disaster into a minor inconvenience.
Question from Norm (1963):
Anyone want to take a shot at a strange problem? It seems my 63 LeBaron starts and runs smoothly when cold and warming but after a hard run on the road it idles rough. If I let it keep idling it smoothes down again. Only other symptom is it won't take full throttle acceleration , it speeds up and slows down rapidly. Timing is at 10 degrees BTDC at idle points but won't set higher than 26 degrees. Just replaced fuel pump as the car quit on me altogether . There was a fair amount of rust in the pump and filter. No unexplained fluid losses , so I do not think there are any internal cracks. Anyway this is a new behavior and the car has not overheated nor does it get cold enough here to freeze.
I had a similar problem with my '75 440 car, changed fuel filter, fuel pump, did a regimen of tank additives but the engine would at no specific time or warning have hard hitting stutters, and a lot of times just quit going down the road once it warmed up. Set all Thermoquad rod and metering settings correctly, sprayed exterior of carburetor with copious amounts of cleaner. Nothing seemed to help. Problem was that I never knew when the problem would occur going down the road. Then it suddenly went away, no clue why, ran fine for about 9 months. Two weeks ago I fired the car up and while it was warming up the motor fluttered to a stop. Spun it quite a while, car was getting gas to the point that it became flooded, one mechanic tapped on the coil and boom....she fired....got it home, next day dead again. I replaced the coil. All this time it was an erratic coil when all the time everyone assumed it must be fuel related.
Your mention of crud in the fuel system certainly hints at some loose particles causing havoc in the carburetor. I did not quite understand your description of the full throttle response: are you saying it stumbles on initial tip-in of the throttle, then pulls OK after that, as if it had a problem with the accelerator pump? Or are saying it runs lumpy continuously all the time you are on the accelerator hard? This would be an internal leak or dribbling from the high speed jets. Is this an AFB? Assuming it is, I suspect you are going to have to give it a good cleaning out on your kitchen table with some carburetor cleaner spray and a kit from the parts store. These are really pretty bulletproof carburetors, and not difficult to take apart, clean out and reassemble. A good kit will guide you all the way. Your mention of timing is interesting also. Are you saying the timing advances to 26BTC from an initial setting of 10BTC? Is this the action of the vacuum advance plus the centrifugal advance? I don't have a manual for your engine, but if this is your picture, it sounds about right, although I would expect serious pinging at that initial timing setting. If on the other hand you are saying your point dwell is only 26 degrees, that is way too small, (your points are too far apart), adjust them to 28-32 degrees and your car should run much better.
My 65 Convertible has a spark problem. Does the negative side of the coil also ground to the engine? Does the negative from battery terminate at both the chassis and engine block? I have voltage to the coil and to the points when the key is turned on. I have a new coil. When the engine cranks I'm getting no spark from the coil wire (coil to distributor cap center hole) Could this be worn points and a bad condenser? I have checked the timing marks and the engine is timed.
I suspect your points are either dirty or not making contact. You should only see 12 volts at the negative post of the coil when the points are open, and this only happens about 1/3 of the time while the engine is running, and is relatively rare with the engine stopped. The points ground the negative post of the coil momentarily to produce the spark, actually the spark occurs when the points disconnect. You should be able to take the distributor cap off, turn on the key, take a piece of insulating material (I use an "orange stick" which the ladies use to clean out under their nails) and move the moveable point away from the fixed point. You should see a spark and the coil should make a BIG spark. If this does not happen, clean the points and make sure the gap is set to around 17 thousandths, and try again. If the contact surfaces of the points look really nasty, change the points and the condenser both, and a new cap, rotor and perhaps plug wires may be in order also. All of these items are readily available at your local auto parts store.
Yes, my guess it is the points. Replace cap, rotor, points, condenser and I would do the wires too!
Question from Norm (1966):
I just installed the Pertronix electronic ignition system on my 66. I was told that I needed to measure the voltage at the coil as a way of knowing whether to short cut the ignition resister or not. Has anybody had any experience with this? I also purchased their high voltage coil and intend to install it.
Reply from Brad:
It says something about measuring the resistance at the positive terminal of the coil, I thing 1.5 Ohms I believe. It also says that it simply won't work if there isn't enough voltage at the coil. Their test is to wire (+) it directly to the battery; if it works this way (and not at the coil) you need to wire it into the ignition circuit foreword of the ballast resistor. I'm ashamed to say I don't own a Multimeter, so.......I did the try-it method. Correct me if I'm wrong but you can't get more than 12 volts from the (+) coil terminal anyway so I gave it a try. Fortunately it works fine, I didn't want that red wire strung all over my engine.
Question from Gary (1966):
I started my '66 Crown tonight (been sitting for over a year) and noticed the ballast resistor was smoking. I shut car down and disconnected battery. Car has been inside and dry. This resistor is fairly new. Anyone have any thoughts?
Reply from Dick:
If it happened out here in the desert, my guess would be it was soaked with packrat piss. Unless it is an incorrect resistor or someone mysteriously replaced your coil with a non-stock one, there isn't any way it would overheat unless the points stuck closed, and if that were the case, the car wouldn't run. It is normal for these to run hot - so maybe it just needs to bake off the accumulated crud.
Question from Ray (1970):
This is the problem, and this is what I've done so far. Problem: The coil does not produce a spark whatsoever. When I point the coil wire to a piece of metal, nothing comes out. The condenser doesn't shock me either when I touch it, so it's not storing electricity. The main cause, it's been sitting since 1993. and some squirrels have lived in it, squirrels who have a particular affinity for pecans. What I've done so far: Put in the battery out of my Fury, a diehard series 24. Car didn't turn over Put in a new starter relay, car didn't turn over. Put in my spare starter, car doesn't turn over. Throw out positive battery cable, build new one, car turns over, doesn't start. Installed new voltage regulator, Borg Warner electronic style. Old one was rusty. Installed ballast resistor from Fury, put the one on the Imperial in the Fury, Fury starts, Imperial doesn't. Put on spare Borg Warner coil. No spark. Put on spare VW Bug BOSCH blue coil, known good. No spark. Put on Fury's coil, still no spark. Broke condenser wire off. Bought a new one, no spark. Put condenser on negative terminal, just like the Fury, no spark. Put Fury's condenser, no spark. now suspect ignition switch. Put remote starter on, bypass switch, nothing. Now I'm mad, assaulted convenient tree with BFH. I have no way of telling how the timing is, because I'm not getting anything out of the coil. I got a hold of a diagram from a 70 Imperial FSM. This thing does not show a condenser on it. It shows a thing called a "Distributor solenoid", and a thing called a "carburetor solenoid". My carburetor appears to be an AFB, which isn't stock. I do have the blue wire that attaches to it, it had a melted plastic connector, but nothing to hook into. Anyone have any idea what this means?
First of all, I think the solenoids you are referring to may be for a CAP or lean burn option. Not going to be the problem. The condenser you are referring to is the one outside the distributor which won't be the problem here. We need to pull the cap off the distributor. That is most likely the source of the problem. I would replace the whole package, points, condenser, rotor and distributor cap. Talking less than $20.00 to do this. Set the gap at approximately .018. I would lay down a small wager, it will fire! If the car has sat that long, and the points may have been closed at the time they have corroded or rusted. You are not going to get fire form the coil with defective points. These are things you would want to do anyway even if it was running but like I said, I think you will have some progress.
I have to agree with Bill here. In cases like yours, its usually the distributor. The term "carburetor solenoid" to me means "idle solenoid", which would tend to make me think, like Bill said, either California emissions, or part of a lean burn set up. If the those solenoids are part of a lean burn set up, the carburetor would be a late 70's Thermoquad not an AFB. AFB's as far as I know came with mechanical chokes, in the late 70's all car manufacturers were switching to electric chokes and idle solenoids. If for some reason you had a late 70's Thermoquad from a 400 v8 plopped on top of a 70' manifold, there wouldn't be anything for it to hook up to. So anyway, another approach is if you're not real keen on putting in points, you could always just buy a point distributor. They are about $40.
Two things I would check first.
#1 Do you have voltage (6 to 8 probably) on the positive side of the coil with the key in the run position? If not then you know your problem is somewhere in that circuit. You can temporarily run power from the battery to the coil positive to see if it will start. Note that this is very bad for the coil that is designed to run on the lower voltage coming off the ballast resistor.
#2 Replace your points. Many times the points corrode after sitting for a while and don't work anymore. You might be able to get away with sanding the contacts of the points and reinstalling them but points are pretty cheap.
Follow-up from Ray:
I did a continuity check, and current was getting through there, in theory. Don't know if I have proper voltage there though. I'm going to have to check this in the morning. But would bad points mean I'm not getting spark from the coil? Also, are there any ignition items that require good grounds. The battery has a good ground. How about the condenser? Does the coil bracket double as a ground for anything? There's squirrel snack leftovers all over the engine compartment, so maybe something isn't grounding right.
Do you have 12v at the points. You can measure this with a meter or test light. If you don't have a test light you can kluge one out of a 12v bulb. Tape one wire around the metal body, stick it to ground and put the center tip on what you want to measure. If it lights you got voltage. Next check voltage going to the coil, trace the wire from the distributor. Without that you ain't going to get a spark. I'm betting you have no voltage. I had a wire burn in to inside the insulation once. Left me stranded on Key bridge in DC rush hour. Like to have NEVER figured it out.
Clarification from Don:
In most 12 volt systems you only have 6-8 volts at the point, hence ballast resistors for Mopars Ford and GM use a different method for this.
Question from Carmine (1973):
I've been working on the old '73 Charger lately, (400 Magnum) and I've finally un-done enough of the previous owners stupidity (flex-fan, RTV carburetor gasket, wire harness wrapped with white tape, etc.) to begin dialing it in. The car currently has a Thermoquad carburetor that appears recently rebuilt. I've gone through the ignition system and replaced all the "tune-up" parts. I have both rich end and leaned the carburetor. The problem I'm left with is overall "doggieness" and moderate "pops" through the exhaust. Timing is set at 10 degrees BTC. (Which seems about right, judging by spark knock). I might be inclined to think this was a weak ignition coil, but the generally problem-prone Thermoquad makes me want to think carburetor. Has anyone else encountered this exact problem? Thought I'd ask before I attack the problem again Monday. Thoughts?
"Pops" through the exhaust are almost always an electrical problem - a momentary interruption of firing which causes a rich mixture to collect in the exhaust system, then let go with a bang (more or less, depending on how many firing intervals were missed) when it comes back to life. Remember our trick to impress the girls when we were teenagers- turning off the key for an instant while coasting - makes a wonderful noise, and our dad never did figure out why we were always blowing up the muffler ( or maybe he did it too?).
Is the carburetor the OEM one, as I recall they were quite lean to start with, and you and I both know how finicky they can be for leakage and all that garbage. Are the pops in the exhaust you refer to after firing, as opposed to backfiring?
Please check your timing chain, sounds like the cam is running a few degrees in back of the crank.
Question from Jeff (1974):
I am having a problem with a 74 Imperial. It starts and runs well when cold but when the weather is warm, it stalls when hot but only when put into gear. It always restarts and seems fine when in neutral or park but as soon as you shift into drive or reverse, it dies and will not move again till it cools down although it always starts. Any ideas? The factory service manual lists carburetor stuff (nothing has changed since he has had the car Carter Thermoquad) It also lists the coil and the fuel pump as well as a faulty coil, but as it only stalls when put into gear, I am a little stumped.....
Follow-up from Jeff:
To fix my problem, I got a new fuel pump ($15) and a new coil ($20) and put them both on with a minimal amount of effort. The problem seems cured. Drove the car all last night and it did not stall once... I am not sure which it was, but the fuel pump looked factory and the coil was leaking oil from the center hole so both were suspect.
Question from Carl (1981-1983):
I need some advice in curing a problem that has thrown me. About two months ago my 81 w/ intact FI started stalling during the warm up period. I am defining the warm up period to be about 15 minutes. She starts every morning beautifully and then will stall, usually three times, before she starts running consistently. I have hard wired the fuel shut off module ground. I have installed a new in tank fuel pump. I have replaced the fuel filters. I have re-calibrated the computer. I have checked the back pressure on the converter. I need suggestions on what to try next. She will stall on freeways at 65 mph, or at idle, or at a restarts after she cools off some, but she always starts perfectly the first time in the morning and she runs consistently after the first 15-20 minutes and at least 3 stalls in that time period.
I have experienced your problems some years ago and will pass on to you some ideas to stop the problem. My problems always occurred after some warm-up period. Upon cooling, it would usually restart. It is my opinion that the fault is Ignition rather than Fuel. During warm-up, when it stops, remove the Air Cleaner Cover and have someone go thru the Start cycle, you should see some fuel squirting from the Spray Bars. It's a good idea to have grounded the secondary wire from the coil to the distributor prior to Start. Two tries may be necessary to get the fuel to spray. Recycle the Ignition key to Off, then repeat. If you get the fuel, proceed to Ignition tests. Remove the 10 Way connector from the rear of the Computer, and connect an ohmmeter between connector terminals 5 and 9; you should read 150 to 900 ohms. If yes, connect one ohmmeter connector to a good ground, the other to connectors 5 and 9 alternately; there should be no continuity; if there is, disconnect the Pick-Up Coil connector at the Distributor and connect one lead of the ohmmeter to ground, the other to each terminal, on the Distributor end of the connector, there should be no continuity. If there is no continuity, check the wire from the Computer to the Pick-Up Coil for a short to ground, this may be an intermittent thing, so carefully trace the path and look for abraded insulation on this wire. If there is continuity, replace the Pick-Up coil. Because you cannot predict when this fault will occur, I have been able to warm the Pick-Up coil with a hair dryer, while the ohmmeter is connected to the two wires, and in less than ten minutes, under mild warming, the ohmmeter will open and this will indicate that there is a problem within the Pick-Up Coil - replace it. There were a bunch of 81's with this problem and it was due to a bad production run of these coils.
I think I am the guilty party for the suggestion about bypassing the ASD. Even though it did not make your problem go away, the fact that doing so had no effect on the problem adds to our knowledge about the situation. Now we know that failure of power supplied to the fuel pumps or the EFI/CCC system is NOT the problem. You can put that whole category of investigation on the back burner. If the car stalls when it is just sitting there idling normally, with a good strong steady idle, and then just dies on you, then restarts with no special fiddling (please verify that this is indeed your symptom), I come around to a suggestion Bob Harris made a while ago, namely a possible temperature induced momentary failure in the distributor's pick up coil. I think we talked about this possibility one time before. Did you replace the pickup coil at that time? Bob suggested that if the pickup coil is suspect, one could take a VOM and measure continuity from one wire to the other of the 2 wire pickup coil connector ( it comes out of the side of the distributor, unplug it and connect to the end which goes into the distributor), while heating the coil assembly with a hair dryer. When the coil is OK, you will see a quite low resistance (I forget the number at the moment, but it would be no more than a few hundred ohms, probably much less) and when the coil opens, you would see very large resistance, over 10,000 ohms for sure. This is an easy test to make, and can be done without disturbing any of the settings. I am not absolutely sure this will always identify a failing part, however, perhaps Bob can shed some light on how foolproof this test is. Personally, if I suspect this part, I just replace it with a new one, since they are cheap and relatively easy to change, see procedure below. They are available from NAPA, and possibly other parts sources. You need to remove the reluctor magnet to get at the pickup coil to replace it (it comes only as a complete assembly, already attached to the "breaker" plate). I think it is a good idea to replace both pieces at the same time (pickup coil and magnet), since they are cheap, and you might damage the old magnet getting it off. If you decide to replace these parts yourself, be advised that you will have less trouble in the long run if you pull the distributor to work on it. There is only the one 2 wire coil connector to deal with (after you get the rotor and cap out of your way), but of course you will have to be careful to reinstall the distributor and rotor in the same position that it was in when you removed it, and make sure no one bumps the engine over while it is out, or else you will have to go to plan B to find #1's TDC point. Then you will have to reset the timing (12BTC at idle). Be very cautious when pulling the magnet off the end of the shaft, if you put any more than a few pounds force on it, you can easily damage the bottom thrust washer, which is pretty feeble. It would be best to hold the shaft itself rather than the distributor body to pull the magnet; this is difficult without removing the distributor. Even if you do not disturb the distributor, you will also need to set the gap from the tips of the 8 finned rotating magnet to the pole piece of the pickup coil to .006 ", which will take a non-magnetic feeler gauge. This will be hard to come by, I use a piece of .005" shim stock (brass) and set the gap a little loose. I'd like to hear what Bob has to suggest on this problem too, he has a world of experience with these cars and their teething problems, and I gather this was not unheard of even when the cars were new. I'll be quiet until I hear more.
Question from Ed (1981-1983):
Well, I spent a few hours this afternoon working on my 82's EFI. I replaced the gasket at the base of the air cleaner with a new one from Brad's NOS. I also replaced the fresh air duct and pre heater hose with new NOS ones too. I removed the Fuel Pressure Switch and sprayed it out with carburetor cleaner and also sprayed out the assembly that it attaches to. The spec's on it checked fine, about 3 or 4 ohms of resistance. Now came the fun test: I drove to the store, about five miles away. The car runs GREAT. After about five minutes, I came out of the store and attempted to start the car, and it would NOT restart. So I took my handy dandy Volt-Ohmmeter, removed the air cleaner cover, and checked the FPS. It was fine, reading only 3 or 4 ohms. Still the car would not start. I repeated this several times, and could not get any hint of a start. How #$%*ing (fill in obscenity of your choice, though I showed my New York heritage, using one of my favorites at the time!) FRUSTRATING!!! So I stepped into a little diner nearby and had dinner. I had left the hood up on the car, so it would cool off, and now it had sat for about an hour. Sure enough, it started IMMEDIATELY, without hesitation. Now when I got home, I let the car sit about 20 minutes, and again it would not restart. I did the Dick B. trick, and dumped a few ounces of gas into the throttle body intakes, and tried to start it again, but still it would not start! I am wondering if perhaps it is a lack-of-spark problem, and not a fuel problem. What I need to do is have a helper handy when this happens again to crank the motor while I hold the coil wire near the exhaust manifold, and watch for a spark at the coil wire. Unfortunately I am home alone tonight, so this will have to wait until it recurs. I am thinking that perhaps the problem is with the ignition coil. Don't they act like this when they are failing, i.e. refuse to create a spark when they get hot, but work normally when cool?
Yes, it is usually reported that a failing coil acts up when it is hot, and is OK cold. However, in my gray bearded old life, I have yet to see a genuine case of a failed coil unless it is bad in all conditions, or leaking oil. Maybe I've led a sheltered life. The coil is cheap and readily available, so give it a try if you feel like it. The NAPA number is IC 27. Before you do that, though, since you have a VOM, why don't you try measuring the resistance between the two wires in the connector from the distributor (the plug is a separate connector pretty close to where the fuel lines enter the HSA, it's black and hard to see, but it will pull right apart). If you get the car into the state where it won't start, check to see if there's continuity between those two wires - the ones that come from the distributor. You should see at most a few ohms. If there isn't and continuity at all, you've found your problem, an intermittent pickup coil in the distributor. These are also cheap and readily available, but they are a little tricky to install. Please don't be insulted, but I have to ask: when you poured the dollop of gas into its little maw, you did just loosen the wing nut a turn or two, pour the gas in the center hollow of the lid, then retighten the wing nut and try to restart, right? Reason I ask is if you really poured it right into the throttle bores (removing the air cleaner lid), you might have overdone it or left something not airtight when you tried to restart.
I experienced a similar problem (on a 48 Plymouth!) and the problem wasn't the coil -- it was the connections to the coil. I think the distributor side (-) nut was loose and the car would behave like you described but it would also cut out while driving. The engine wouldn't restart. Waiting 20 minutes with the hood up would allow an immediate restart. I carried along spares of everything I could think of, determined to solve the problem. When the problem occurred I went to change the coil and found the loose nut. The problem did not come back.
Question from Ed:
I am thinking that perhaps the hot-start problem is with the ignition coil. Don't they act like this when they are failing, ie. refuse to create a spark when they get hot, but work normally when cool?
Yes, it is usually reported that a failing coil acts up when it is hot, and is OK cold. However, in my graybearded old life, I have yet to see a genuine case of a failed coil unless it is bad in all conditions, or leaking oil. Maybe I've led a sheltered life. The coil is cheap and readily available, so give it a try if you feel like it. The NAPA number is IC 27.
Before you do that, though, since you have a VOM, why don't you try measuring the resistance between the two wires in the connector from the distributor (the plug is a separate connector pretty close to where the fuel lines enter the HSA, it's black and hard to see, but it will pull right apart). If you get the car into the state where it won't start, check to see if there's continuity between those two wires - the ones that come from the distributor. You should see at most a few ohms. If there isn't any continuity at all, you've found your problem, an intermittent pickup coil in the distributor. These are also cheap and readily available, but they are a little tricky to install.
I agree with Dick, check your pick up coil for resistance next time she won't restart hot. If I remember right it should read about 300 ohms if is in o.k. When they start heading south, they are know to open when they get hot, and close when they cool off. They can leave you completely stranded when they finally decide to die. It's a quick easy check to rule this component out. It tends to get over looked and if it's bad it will cause a lot of time, expense, and frustration. So check it out.
Ed, I experienced a similar problem (on a 48 Plymouth!) and the problem wasn't the coil -- it was the connections to the coil. I think the distributor side (-) nut was loose and the car would behave like you described but it would also cut out while driving. The engine wouldn't restart. Waiting 20 minutes with the hood up would allow an immediate restart. I carried along spares of everything I could think of, determined to solve the problem. When the problem occurred I went to change the coil and found the loose nut. The problem did not come back.
Question from Scott (1981-1983):
Hopefully someone can answer my question as I'm totally lost on this subject! After grounding the a.s.d.m. as recommended and checking the fuel press. switch, which is bad and the new one will be installed tomorrow, after the car sits about an hour or more, spark from the coil wire is lost. Does the EFI control ignition spark? The coolant temp switch checks out ok also. Any suggestions would be greatly appreciated. I'm really tired of waiting an hour or more with the hood open till it cools down and starts.
Reply from Jack:
Sounds like the coil is bad. Get a multi-meter and check its resistance when its hot and the spark quits. Can't remember the exact value to look for but a dead giveaway would be an open circuit between the + and - terminals or an open between the + and high voltage (coil wire) terminal.
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