Sparatic ignition problems becoming worse

Tiny
AUBREY OUTSIDER SOMMER
  • MEMBER
  • 1973 PLYMOUTH FURY
  • 5.2L
  • V8
  • 2WD
  • AUTOMATIC
  • 125,000 MILES
My car is having ignition problems. It will start in the mornings and occasionally stall out when I either hit a bump or go slow while getting ready to park. After this it seems like I am not getting a spark as it refuses to fire. I changed the coil to try to fix the problem but that did not help. The starter is still working strong. While pulling a spark plug to check for spark my ratchet connected from the spark plug to the fender and I saw a spark while the spark plug did not even have a wire on it. I am starting to believe it may be multiple problems going on simultaneously. Any help would be greatly appreciated.
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Monday, February 6th, 2017 AT 11:22 AM

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Tiny
CARADIODOC
  • EXPERT
When the engine stalls, try to keep it in the bad state so the problem can be diagnosed. Pull the distributor wire out of the distributor cap, and hold that end close to the engine. Watch for spark there when a helper cranks the engine. If you have no spark there, watch for the presence of a single spark when the helper turns the ignition switch off.

How many pickup coils are in your distributor? Each one has a black and an orange wire going to a two-terminal connector. Some distributors have two of those pair of wires. Some have only one pair.
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Monday, February 6th, 2017 AT 6:11 PM
Tiny
AUBREY OUTSIDER SOMMER
  • MEMBER
I only have one coil. My distributed does not use points, it instead runs to a control unit.
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Tuesday, February 7th, 2017 AT 12:31 PM
Tiny
CARADIODOC
  • EXPERT
I never said anything about breaker points. As with almost all innovations that directly benefited car owners, Chrysler was the first develop a fully-electronic ignition system. Your ignition system was first used on Dodges in 1972, (I had a bunch of them), and on Chrysler's and Plymouth's in 1973. I am asking about the pickup coil inside the distributor that triggers the ignition module. Some versions used two of those inside the distributor. One was switched into the circuit during starting, then the other one was switched in once the engine was running. The switching was done with a relay, and that relay is a good suspect for an intermittently-failing ignition system.

Most of these ignition systems used only one pickup coil. A real common problem on either system was the dual ballast resistor on the firewall, but those will never fail intermittently. Once one of the resistors burns out, it will never magically heal itself again. What you might look for though is a rusty terminal that is creating an intermittent connection. You can identify that by wiggling gently on the connectors while the engine is running.

Next, check the ignition module to be sure it is bolted solidly to a rust-free point on the body sheet metal. That is one of the electrical connections.

Did you do the spark tests I described earlier?
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Tuesday, February 7th, 2017 AT 2:50 PM
Tiny
AUBREY OUTSIDER SOMMER
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I did not. I was able to get her to fire just by turning the key so I could check the ballast. What am I looking for in the "wiggle" test?
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Tuesday, February 7th, 2017 AT 4:48 PM
Tiny
AUBREY OUTSIDER SOMMER
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And it is a single coil. It has a little bit of play but does not seam overly loose.
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Tuesday, February 7th, 2017 AT 5:17 PM
Tiny
CARADIODOC
  • EXPERT
The dual ballast resistor has a white two-wire connector on each end, (They can only be plugged in one way, but either plug can go on either end). One has two dark blue wires in it. Those are the two plugs to wiggle. Bad connections are not common, but we don't want to overlook the possibility.

The green arrow on your dandy photo shows where the wires for the pickup coil flex repeatedly. An intermittent connection there can cause intermittent stalling, but usually at a higher road speed, like 35 - 40 mph or more.

My nifty red arrow is pointing to one of the eight points on the "reluctor". It passes a magnet on the pickup coil under the rotor by the blue arrow. If the pickup coil was worked on recently, the air gap is critical. You must use a brass feeler gauge because a regular steel one will stick to the magnet and give a false feel. As I recall from my '78 LeBaron, the gap was supposed to be 0.018", but in later years I remember reading specs of 0.008" and 0.012". Regardless, the gap is tight enough that it could be adversely affected by worn bushings causing the distributor shaft to wobble.
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Wednesday, February 8th, 2017 AT 6:36 PM
Tiny
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You sir are a scholar and a saint. So I should see if I should tighten it up and see if I should see if I can tighten it up or should I just fix the entire distributer?
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Wednesday, February 8th, 2017 AT 6:51 PM
Tiny
CARADIODOC
  • EXPERT
Hold on. I'm just giving you some suggestions based on my experience from owning a real lot of these cars. I actually never had much trouble with them, so some of what I'm sharing comes from other stories I've heard over the years. Since I have a lot of parts for these cars, I would stick in a different distributor to see if it solved the problem. One more that I forgot is the pickup coil can develop an intermittent connection inside that breaks when it gets hot. While driving, natural air flow keeps it cool. When a hot engine is stopped, as in when stopping for gas, "hot soak" allows engine heat to migrate up to the distributor and cause that bad connection to occur. The symptom is almost always a failure to restart until the engine has cooled down for about an hour.

I'm reminded that I did have a failed ignition coil a few years ago on my '88 Grand Caravan. It caused intermittent stalling problems, mostly on hot days, for a year and a half before it finally failed completely and I could find it. Up till then, it failed just long enough for me to get the hood open, then it worked fine again! Ignition coils are USUALLY not intermittent, which is why we tend to overlook them.
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Wednesday, February 8th, 2017 AT 7:15 PM

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