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| Weird ignition problem...maybe? https://slantsix.org/forum/viewtopic.php?t=31504 |
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| Author: | polkat [ Sun Oct 05, 2008 12:01 pm ] |
| Post subject: | Weird ignition problem...maybe? |
While I usually don't ask V-8 questions here, I always get good advice here, and the question involves the stock Mopar electronic ignition, which is basically the same ingition as the slant 6. This is a '73 Dart with stock electronic ignition and a 318 with Edelbrock. This started a few days ago. After the engine warms up I can be sitting at a light or at full speed on the highway, and quite suddenly the engine dies. I check to see if it's getting gas...yep. So I check for spark. The one time I did this I was on the side of the highway in rain, so I'm not sure, but I couldn't see any spark (plug wire end about 1/4" from ground) at all. There is no problem with cranking when this happens. So I let it sit for about 20 minutes and then try it. Starts right up. Five miles later it dies again. Same thing...let it cool and it starts. This doesn't happen until the engine is warm. The choke is fine. When it dies, there is no flutter like it's run out of gas, but just a very quick death. I have come to two conclusions; 1. Something in the ignition (the control box?) is overheating and dying, then coming back to life when it cools. 2. The Edelbrock carb (1400 series) is leaking internally and flooding the engine. But again, it doesn't flutter to death like a gas problem would, just immediate death. And that wouldn't account for the apparent lack of spark. So, any ideas? ________ Toyota Noah |
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| Author: | Reed [ Sun Oct 05, 2008 12:59 pm ] |
| Post subject: | |
Coil, or distributor pickup. |
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| Author: | slantzilla [ Sun Oct 05, 2008 3:14 pm ] |
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Check your bulkhead connector for corrosion. My '66 was doing the same thing and the blue wire to the ballast resistor was all corroded. It was bad enough I had to cut it on both sides of the firewall and run a jumper. |
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| Author: | SlantSixDan [ Sun Oct 05, 2008 4:14 pm ] |
| Post subject: | |
Could very easily be the ignition control unit. You can try diagnosing the problem by starting the engine, then shutting it off and heating up the control box with a hair dryer or droplight. Get it good and hot, then try to start the engine. If no go, you've found the trouble. But yes, it could also be a different component failing in response to heat — the coil or distributor pickup, as previously suggested. |
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| Author: | polkat [ Sun Oct 05, 2008 9:13 pm ] |
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Well, I tried the hair dryer trick tonight but the ECU never shut down and didn't get very hot. One thing that did happen is that I put my hand on the ECU, to see how hot it was, while leaning on the fender, and my finger fell on the top of the big transistor on the ECU. Nasty little shock!! Is that supposed to happen? The distributor pickup gives a solid 600 ohms (right where it should be) and I've tried grabbing the coil when it happens, and the coil is nice and cool. That doesn't mean that neither of these things are bad, but they seem okay. I tried removing the ECU and found poor evidence of a good ground from box to inner fender, so I cleaned all the contact surfaces to clean metal, and also ran a ground wire from one of the mounting bolts to the negative side of the battery. I also checked for clean tight connections and for broken wires where I could. Fixed a few things, but nothing that could cause the problem. I'll know in the morning if any of this helped. I suppose it's still possible that it's a fuel problem (it would have to be a flooding problem, since the accellorator pump shot is okay when this happens). An internal carb leak could flood it. Just doesn't feel like a fuel problem. ________ headshop |
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| Author: | THOR [ Sun Oct 05, 2008 10:57 pm ] |
| Post subject: | |
Quote: Coil, or distributor pickup.
If you have an extra coil hanging around that you know is good, stuff that in there and see what happens. How is your charging system? I know that on my old car, the alternator wasn't in that great of shape, and would occasionally stop charging completely, which in turn puts a tremendous initial load on the battery. It may be dropping the voltage too far to sustain the ignition system. Does it happen more at night? Or during the day? Or neither?~THOR~ |
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| Author: | KBB_of_TMC [ Mon Oct 06, 2008 11:34 am ] |
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Intermittent problems like that are almost always electrical. At highway speed your A/F can be way off w/o stalling. Don't overlook the possibilty of a flaky coil-to-dist wire... I had one that caused me fits because it tested OK with a DMM, but would conk out sometimes. Finially it stayed dead and I found it. I also had similar problems with old coils, ignition boxes, the big 5-pin plug, wires, etc. It could also be a any number of flaky connections, anywhere along the line from the ignition switch on down. Don't forget the grouding of the ignition module - that's important. Those screws often make a poor ground after many years. Also, sometimes the 5pin plug just gives problems internally. HV problems are especially tricky to track down. Sometimes it's just easier and cheaper to replace everything that easy (coil, module, pickup, wires) than to much around trying to locate the bad part. Any HV component with a billion sparks or 30 years on it ought to be very suspect anyway. |
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| Author: | jar84203 [ Thu Oct 09, 2008 4:18 pm ] |
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Have you had the alternator tested. If it's not producing enough power the engine will run on just the battery eventually draining it. Just a thought |
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| Author: | polkat [ Thu Oct 09, 2008 11:48 pm ] |
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Thanks guys. The battery is fine. I've decided to do the HEI conversion with a different coil. Hopefully this will handle the problem. Also found a problem with the fuel pump which probably contributed to the problem. ________ Yamaha Virago 1100 |
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