ZZtop

My car wouldnt start earlier. It would turno over but not fire. I put the key in and out a few times and then it fired. It started first try later on at the gas station and library, then while driving home it just died!!! I have tried jiggling the key cylinder, putting the key in and out and checked the coil connections, NOTHING. It will turn over, but not fire. What could be the cause and how do I diagnose. Is there an ignition switch somewhere on the key cylinder maybe...I only know old school distributor ignitions.

This is my daily driver so any and all help is appreciated, the sooner the better.

shoebox

Putting the key in and out is not going to do anything, unless you were turning it ON after you puti it in. If you did this several times and it started again, it might mean the fuel pump.

I am assuming you are meaning it cranks but will not start. I also assume you have no SECURITY lamp.

Fuel and spark are the things that you need to verify are present. Correct fuel pressure can only be measured with a test gauge.

ZZtop

Yes, it cranks but will not start. I can hear the fuel pump turn on when I turn the key into the on position, and then turn off. Sounds like normal. I may have a security light, hmm, would this be on with all the other lights when the key is in the on position? If so, what does that mean?

Also, could it really be fuel even though it acted up then started fine several times and then just died while driving. No sputter or anything, just shu OFF.

HBHRacing

Wen you turn the key to teh on postion the light will come one and should go out after a few seconds. if it stays on or flashes thats your problem

GreenDemon

Does priming the fuel system help? Or is it more erratic than that?

If it's erratic, you could be another person effected by a bad ignition switch. I used to think this an obscure problem until I saw the daily thread (or more) on here.

I'm pretty sure mine is on it's way out, because turning the key back and forth to prime the fuel system does absolutely nothing for me. Sometimes it cranks right up, other times could take a little while. But if it doesn't crank up, I usually don't try very long, I just turn it back off and then immediately try to start again, almost always works for some reason.

My new switch is in my back seat at the moment, if my results are successful I'll be certain to post on here since a lot of lt1 folks are plagued by hard starting issues.

But I would try to diagnose the entire system first, I've read shoebox's page on replacing the ignition switch and it doesn't look like much fun- I already know my pump is working at least halfway decent though, so I would check fuel and spark first.

But your shutting off problem does sound very convincing as to the ignition switch- mine's done that a couple of times while starting (the entire car loses power- ie gauges go dead as well as if you turned the car off but the radio retains power), but luckily not while driving (yet).

ZZtop

Darn it, I just walked to the car, its a ways away and tried to start it with my spare key also. Still no luck. The security light is on in the on position and while cranking, but I didnt know to wait a while and see if it goes out or starts blinking, errrr. Guess I will look at that tomorrow.

Where is the ignition switch you are mentioning, what does it look like and how do I test it?

Thanks for all the help so far guys.

GreenDemon

Check out shoebox's tech page, link is in his sig.
Help on that and many other things you may want to know about.

ZZtop

Alright, did some metering and I think Im getting somewhere. This is what I found:

VATS checked out fine, resistance at connection matched key.

With key in the run position, there is 14 Volts at the ICM. Metering the red/black runner and the ground wire.

With key in the off position, no voltage at the ICM.

I believe the ICM is downstream of the ignition switch so this would lead me to believe the ICM is bad. Is there some way I can meter voltage to the coil or is that not possile cause the ICM tells the coil when to fire??? Im still not 100% on how the ICM works.

Any thoughts guys?

ZZtop

Anything guys, I would like to get the car fixed today. Parts stores are closed Sunday.

HBHRacing

your gonna need to do the basics.. check for spark and fuel. if you say you primed the key several times and it started then like Rob said possible fuel pump or pressure problem. I would start there with a fuel pressure test making sure that you ahve enough pressure and the pressure doesn;t bleed down.


as for the ICM test... you can find that and a lot more no start information on my LT1 NO START DIAGNOSTIC PAGE

ZZtop

I got it to start by putting the key in and out of hte cylinder a bunch of times and then on the next try it started. I think it may have been a coincedence. I can hear the fuel pump prime everytime I turn the key. Also, would a fuel pump make the car not start, then fire right up 3 times in a row and they make the car just shut off while driving? It didnt sputter or anything, just stopped. I really dont think its fuel, but agree that I should check it. I tested the coil today and it is fine.

HBHRacing

how did you test the coil. The best thing to do is wait for it to not start then test for spark and fuel and see if you are lacking one of them...

ZZtop

I tested the coil for resistance at each of the connections, using the test on shoebox's page. I got 8ohms at each connection. Ohh, and I replaced the ICM and that didnt fix it. Getting the girlfriend to help me check for spark right now.

ZZtop

NO SPARK!!!! Now what???

ZZtop

I have no checked for pulsing ground at the injector, but I dont know how to setup my DVM to do this?


Not sure if this is correct, but I touched the positive lead of the DVM to the green wire on the injector connector and the other lead to ground. With the key in the on position I had 12V. When cranking it stayed at 12V, I didnt see any pulsing.

If I did this right, then that would mean its opti related, like maybe the optical sensor?

Errr, that opti is only a few thousand miles old and I had it put in by the dealer along with a brand new optical sensor harness. ERRR I bet they woulnt own up to it either.