I thought I had corrected the problem but it is still there. The car will start but when releasing the switch to run position, it dies. I have replaced again every component of the start circuit to no avail (including resistor, control module, and ignition switch). I noticed sometimes by removing and replacing the terminal block at the firewall (middle one) that it may start. I have cleaned and tightened those connections. It may go days without the problem and then it may go days without starting no matter what I do. If it is a short in the wires, I would think it would be more likely to go out when drig down the street. This only happens when the vehicle is parked and off and then it will not start. I have thought about vapor lock but it happens after sitting all night and I see no evidence of it being vapor lock such as boiling over. What is going on here? Is it possibly the alternator?

Hope I didn't miss a step from your earlier posts, but here goes:

The start
You mentioned before, that you weren't getting power at the coil (when it's giving you grief), so it's a short in the wiring, not the alternator. Possibly the ignition switch, a corroded wire or partially broken connector. I don't know if they used fusable links, but they'd be pretty old/suspect. I'd get out the test meter on a good day, and have someone wiggle all the wiring, key, any connections, till you saw the voltage flutter in the run position. You might disconnect the coil + wire and connect it to a test light while wiggling stuff.

If it's not working (bad day), I'd get the wiring diagram, and test at every reachable connection till I narrowed the problem to a more specific point of breakage. (in the ignition run circut)

This is a nasty gremlin!

Hope this helps squash it.

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1980 Aspen 225 super six

I know these conditions don't always make sense but if there is a short why does it NEVER EVER kill the engine while I am driving..the bumps and all I would think would cause a short to manifest itself. Instead, it may run fine all day and then I park it and try to restart it and that is the only time this happens. It will start in start mode just fine but in run mode it dies. Temperature doesn't matter nor does it matter how long or short after running I try to start it. It also doesn't happen every time. I replaced the switch and every component in the ignition circuit during initial restore. I have since replaced again the module, resistor and switch. The under hood harness is also brand new including the one and only fusible link. It seems like the link is in the circuit providing juice to the car from the battery. If it were bad, would it not cause it to be totally dead? I even tried bypassing it when it wasn't working and it still did not run. I suspect the dark blue wire because it is in that middle connection block and runs throughout the ignition circuit. I may unwrap the tape from the harness, maybe a splice has gone bad and I'll reclean and tighten the terminals again. This is so strange. Thanks and if anyone has other suggestions...

What voltage do you read at the coil with the key in the "run" position? Should be ~8volts.

Are you using a stock coil or aftermarket?

-S/6

I get 6.8 volts at the p[ositive side of the coil. The battery is perhaps a bit run down with all the start tries. I will say it has started OK all day. I have been systematically cleaning and tightening all terminals at bulkhead and fuse box. I try to start it each step of the way and it has been working fine. My coil is a replacement one that is stock.

6.8 volts at the coil is a little low---and in your no start situations the voltage may be low enough that the coil is not receiving enough voltage to create a spark that can jump the plug gap.

I would start looking at the coil + wire for indications of high resistance (cracked insulation, corroded connections/splices, etc), between the coil + terminal and the Ballast resistor.

Seems like you have checked cleaned most things, but have you cleaned the ECU contacts and mounting points as well?

-S/6

Yes, I cleaned all of that. I also added ground wires to components such as that which are mounted to the sheet metal. I know sometimes that can be a problem so I made ground wires connecting them to the negative battery terminal. I noticed when running that the coil pulls over 9 volts. Would a lower battery and an electric fuel pump running pull some voltage from the coil and cause it to read low? All the harness wires are new. I have been cleaning ALL contacts just to make sure. I will also pull the tape off the harness where the blue wire splices into multiple other blue wires. Perhaps there is a problem there.

If your running an electric fuel pump I hope you have a better then stock alternator. Stock alternators (even those higher power 40-50-60a versions) don't put much out at idle. Whatever they do put out at idle an electric fuel pump will gobble up.

I think the alternator is stock specs. It is about 2 years old. The fuel pump had been on for quite some time before this started. I haven't noticed any battery depletion and it recharges the battery quickly after it gets drained when trying to start with this mess. I have a Holley pump that is the low pressure variety if that makes any difference. Anyway would an insufficient alternator cause these start problems? If so I can always swap a larger one on. Thanks.

Yes, over time low alternator output will deplete the battery and give you low voltage to the coil.

What rpm are you idling at, with the electric pump running, and what is the battery voltage? Also what is the battery voltage with everything off?

I'd think of 2 things:

starter relay and ignition switch... since you say you replaced everything... you got a new ignition lock drum or you're using your old one? also... I assume that the ecu is brand new...?? are the contacts on the back of the ignition swith clean and rust free? I mean, the wiring portion (female) of those.

Your A/T bulb is running fine?

good luck. I had some sort of the same issue in the past and is as annoying as you can get for a daily driver

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

The lowest I can get it to idle (with low idle screw backed all the way out and high idle screw not engaged) is about 1,000 rpm. I did not replace the lock drum because it did the same thing manually operating the electric switch. it starts instantly and then will die. However, it is now performing fine again...I wonder for how long this time.

...I think there's more to this than an electrical problem... Why do you suppose it won't idle down?

D/W

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If it ain't broke, fix it!

Dennis, that also struck me as being odd.

But, depending on how much current that pump is drawing, the alternator may only be able to power it when engine rpm is higher. Not enough juice = ignition issues = won't idle.

When you say you come back to start it and it won't start... the starter relay won't click? Or the relay clicks but the starter turns too slow? Any other details you can think of?

Get your volt meter out and check your battery, especially at the times it won't start.

This also may be far fetched but what condition is your starter in? The solenoid may be sticking or shorting out to ground reaping electrical havoc after you release the key and the solenoid tries to disengage.

OK, let me recap the symptoms. When I turn the key to the start mode, the engine starts just fine. However, when I release it to the run position, it quits. If I hold the key in the start position, it will continue to run. I have replaced every component of the ignition circuit when I did the original restore. Once this started, I replaced each component again one by one but it did not fix the problem. This engine has never idled below 1,000 rpm, even with mechanical fuel pump. The car is 73 Duster but the block is 79-80 and the heads 80-82. When it actually runs, it runs smooth and quiet with good acceleration. The only way I have been able to get this problem to go away is to unplug and replug the middle terminal block at the firewall. Yesterday, I took every single connection in the ignition circuit, removed it, cleaned it, tightened it, and reconnected it. It has been doing fine now. I also added ground wires from the negative battery terminal to every component that uses the body as ground. What really puzzles me is why does it never quit when running down the road but it would only do this after the engine started. If it were a short, I would think driving would jiggle it loose sooner than sitting in the drivewau would.