[markzepp820]

my 79' chevy pickup stalls everytime I start it now. It has a 350 with of course, HEI ignition. I've narrowed it down to it possibly being the ignition coil or module. the carb is fine, float level ect... and also check other things too. I narrowed it down to the electrical system. I have a new cap, rotor, plug wires, and plugs. And still does the same thing(starts for a second then stalls). I know the coil and module are the original parts, they say GM on them and look real old. being 27 years old, I'm guessing they're wore out. If these two parts are worn out or malfuntioning, will this cause my motor to stall immediatly after i start it? thanks,
mark

[brian0605]

I haven't seen them do that, but I haven't seen everything. (YET) I have generally seen them cause the engine to not start at all (won't fire). If they are the original parts it would not be wasted money to replace them. Do you have an oreillys, autozone or advance auto near you??? They should be able to check the coil and the module for you. (read the instructions over their shoulder to make sure they hook it up to test correctly) Some of those guys can't pour pee out of a boot........and some are pretty good.Just a tip when you get there look for the guy with the grayest hair. He may not know the most but will probably know his limitations and who can best help you. Good luck If I think of anything I'll try to post it. The ole brains kinda foggy right now "I work the grave yard (9pm til 7am) and it's my bed time.Brian

[techinspector1]

Run a hot line from the +battery to the coil and start it. If it runs, it's the switch.

[xntrik]

Originally Posted by techinspector1

Run a hot line from the +battery to the coil and start it. If it runs, it's the switch.

Boy, you're in for it now. There are some geniuses on this site that insist that GM ignition switches NEVER go bad. (do a search)

[poncho62]

GM ingintion switches never go bad......................

Did I say that?

It's a possibility, more likely a broken wire from the switch to the coil. It is 28 years old...........Check for power at the coil with the ignition in the run position.

[xntrik]

Originally Posted by poncho62

GM ingintion switches never go bad......................

Did I say that?

It's a possibility, more likely a broken wire from the switch to the coil. It is 28 years old...........Check for power at the coil with the ignition in the run position.

I did NOT say that YOU said that Poncho.

I said someone did,

and if anyone is interested enough to see who argued about it last summer...... do a search.

I don't remember...... that wasn't YOU, was it?????

[techinspector1]

Originally Posted by xntrik

Boy, you're in for it now. There are some geniuses on this site that insist that GM ignition switches NEVER go bad. (do a search)

Well, it won't be the first time I've been in for it, or the last.

[markzepp820]

I had the module and coil checked and they are still good and in working order. my guess is the electrical is not the problem. My carb was acting up a little bit when my truck was running. Can a carburetor cause this starting for a second then stalling delimma? thanks, mark

[tnsmith10]

did u put a test light on the positive side of the coil while the ignition is in the run position??? this is not a matter of removing these parts and having them tested., people r trying to tell u that u have a wiring and/or switch problem, that means u either have a broken wire somewhere from the switch to the coil, or the switch itself has taken a turn.(which isnt very likely from what im reading here.) people r trying to help u, try what theyre telling u.

[JamesRS]

I know you've mentioned that the carb checked out okay with float level's etc, but did you check for vacuum leaks? What you are describing could be a cracked vacuum line. The engine will start and once it's running for a second or two the vibration causes the cracked vacuum line to open up giving the engine too much air and starving it for fuel, causing it to die. Try capping all of your vacuum ports on the carb and intake and then start it and see if it still stalls.

[66GMC]

Does it "stumble" and die, or just plain die?
Have you checked for spark after it dies?

[brian0605]

Let's do the absolute basics here,shall we.....Fuel, Fire, and what boys and girls? compression. Well we can conclude that it has "some" compression since it will run. It is apparently getting "some" fuel since it will fire off. You need to determine if it's getting enough. You could hook up a hose to the output on the pump put the hose end in a suitable container and have a friend spin it over and observe the fuel stream. While this is not scientific you can get a relative idea how much fuel is being sent to the carb. My dad used to have a crank time to volume ratio but that was years and a few too many beers ago to remember. Anybody know the Min. pressure??? I'd have to go look it up .It is also getting fire in crank do you still have fire when the key is released to the "ON" position. A test light will give you a relative idea but won't tell you exactly how many volts it's getting. It should be no more than .2v to .5v different than battery voltage. You could try this,continue to hold the switch in the start position and see if it will idle.(*WARNING DO NOT REV THE ENGINE & DO NOT RUN THE ENGINE FOR MORE THAN ABOUT 10 SECONDS TO AVOID DAMAGING THE STARTER) If it will idle move on to looking at the switch or broken or pinched wire. Also remember it is possible to have a broken wire and the insulation look fine. Hope this helps. And I hope no one was offended by my opening statement,I was just having' some fun...............Keep that old iron on the road......... Brian

[66GMC]

Brian has the right idea ... do some diagnostics, rather than just "throwing parts at it until it runs".

That's more or less what I was trying to say earlier, too.

If it sputters and dies ... it's likely a fuel / vacuum leak problem.

If it stops dead, I'd be looking for an electrical problem.

Some systems (eg. almost anything with points, 70's/80's Ford Duraspark, and Chrysler Electronic Ignition, too I believe) run 2 circuits to the coil... 12V on cranking and ~6V on run. My understanding was that you need the hot spark to get the engine fired up, and a lower voltage to prevent burning the points or over-heating a coil.

Being that it's GM HEI, however, I believe that the voltage reading at the positive side of the coil should be approx 12V all the time ... in crank or run, but it may still be possible that you have 2 circuits as well?

Someone with more knowledge might be able to confirm or deny that.

[xntrik]

Originally Posted by tnsmith10

did

people r trying to help u, try what theyre telling u.

Amen, I'm done...... ta ta

[markzepp820]

I'm really thinking my q-jet is the problem to all this. yesterday, when i tried to start it, it coughed like it wanted to run. then next thing i know, my choke plate is on fire! my carb is making a *POOF* sound out the top of it, then a small fireball shoots up! I know for sure the timing is correct. What causes a carb to shoot a fireball??? mark