Strange problem on 95 Z-28, please help!
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Joined: Dec 2005
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From: Kailua-Kona, HI
Does the car ever just completley die while you are driving it. I had a similar problem to what you are saying where the car would run rough once it warmed up but it would cut out randomly. It ended up being the water pump was going bad and the water from the radiator was dripping onto the opti just enough to build up moisture in there. My car was a 93 though so the opti was not vented I believe 95 is vented though. But if you end up changing the opti double check the pump for signs rust or anti freeze around the weep hole.
I also got the same heads up on the water pump from a couple buddies of mine that own a shop. They said to make sure I replace the pump when I do the OPTI as spending the extra $150 to do the pump can save you from having to do the whole OPTI all over again.
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From: Kailua-Kona, HI
OK guys,
I finally got everything back together, and I still have the same problem.
I replaced the OPTI and installed an MSD unit. Went ahead and did an electric water pump as well.
The first try at start up didn't go as planned. Took 6-7 crank overs.
After it started, and ran for a bit, you could shut it off, and start it just reaching in the car with one hand.
Decided to try it again this morning, and I couldn't even get it to sputter, it wouldn't fire at all.
I think I have found the problem though. I could smell some sort of burning/sulfur/electronic smell as I was cranking the car over. Almost like if you use starting fluid/ether on a car and it doesn't fire, but you can smell it out the pipes.
So I went and smelled the pipes, and that wasn't where the smell was coming from. It was coming from the underhood compartment.
After sniffing around a bit, it smeels like a fried PCM. I didn't have time to dig up my old one (the one in the car right now is one I got from MAD Z28 with a tune on it), so I'm not sure if that will be the cure.
Could a bad ICM fry the PCM?
The only part of the ignition system I have not changed yet was the ICM. I swapped over the one from my Trans Am assuming it was still good (TA been sitting for 2+ years).
So I ordered a new ICM, AC Delco that should be here soon. Then I'll swap the PCM and ICM at the same time.
WHat could have fried the PCM?
I finally got everything back together, and I still have the same problem.
I replaced the OPTI and installed an MSD unit. Went ahead and did an electric water pump as well.
The first try at start up didn't go as planned. Took 6-7 crank overs.
After it started, and ran for a bit, you could shut it off, and start it just reaching in the car with one hand.
Decided to try it again this morning, and I couldn't even get it to sputter, it wouldn't fire at all.
I think I have found the problem though. I could smell some sort of burning/sulfur/electronic smell as I was cranking the car over. Almost like if you use starting fluid/ether on a car and it doesn't fire, but you can smell it out the pipes.
So I went and smelled the pipes, and that wasn't where the smell was coming from. It was coming from the underhood compartment.
After sniffing around a bit, it smeels like a fried PCM. I didn't have time to dig up my old one (the one in the car right now is one I got from MAD Z28 with a tune on it), so I'm not sure if that will be the cure.
Could a bad ICM fry the PCM?
The only part of the ignition system I have not changed yet was the ICM. I swapped over the one from my Trans Am assuming it was still good (TA been sitting for 2+ years).
So I ordered a new ICM, AC Delco that should be here soon. Then I'll swap the PCM and ICM at the same time.
WHat could have fried the PCM?
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From: Kailua-Kona, HI
Guys, I changed out the ICM for a new Delco unit, and put my old computer back in and.....
same problem.
At least I got it to fire up this time though.
I am stumped.
WTF else could be causing this no start issue?
MAF? Injectors?
I'm gonna check the fuel pressure one more time, but man, I've replaced just about everything!
Its still doing the thing where it doesn't seem to fire at all while cranking on the first few tries, but when you let off the key it tries to fire up. So weird.
Any suggestions?
same problem.
At least I got it to fire up this time though.
I am stumped.
WTF else could be causing this no start issue?
MAF? Injectors?
I'm gonna check the fuel pressure one more time, but man, I've replaced just about everything!
Its still doing the thing where it doesn't seem to fire at all while cranking on the first few tries, but when you let off the key it tries to fire up. So weird.
Any suggestions?
Burning electrical smells makes me think you might have wires shorting out somewhere or something like that. Also, are you sure the ICM pigtail is making good contact w/ the ICM? After I swapped my opti, that was my problem. C wasn't making good contact, thus the ICM wasn't getting the signal from the opti to fire.
Thread Starter
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From: Kailua-Kona, HI
Thread Starter
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Joined: Dec 2005
Posts: 444
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From: Kailua-Kona, HI
Burning electrical smells makes me think you might have wires shorting out somewhere or something like that. Also, are you sure the ICM pigtail is making good contact w/ the ICM? After I swapped my opti, that was my problem. C wasn't making good contact, thus the ICM wasn't getting the signal from the opti to fire.
Keep in mind that when it does start it runs great.
I'll try the wiggle test on the ICM and see if it works. I also twisted the prongs on the coil for better contact.
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From: Kailua-Kona, HI
Ok Guys,
I think I may have discovered something this morning that is fuel related.
I am not sure on how the LT1 fuel system primes itself, but I am noticing that the pump is not priming each and every time I turn the key forward.
This morning when I tried to start it, the initial time i turn the key it primed, then it didn't prime again until the 5th time I turned it forward, then it took another 7 or 8 times to get it to prime a third time.
When I swapped the fuel pump a few months ago, I could swear I remember testing it and it would prime everytime.
Is this normal?
What could be causing an intermittent problem?
I tested the fuel pressure under various circumstances before I decided to change the OPTI. Looks like I have to run them again to make sure the pressure is Legit.
I think I may have discovered something this morning that is fuel related.
I am not sure on how the LT1 fuel system primes itself, but I am noticing that the pump is not priming each and every time I turn the key forward.
This morning when I tried to start it, the initial time i turn the key it primed, then it didn't prime again until the 5th time I turned it forward, then it took another 7 or 8 times to get it to prime a third time.
When I swapped the fuel pump a few months ago, I could swear I remember testing it and it would prime everytime.
Is this normal?
What could be causing an intermittent problem?
I tested the fuel pressure under various circumstances before I decided to change the OPTI. Looks like I have to run them again to make sure the pressure is Legit.
Thread Starter
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From: Kailua-Kona, HI
So if I was to prime the car in the evening and observe the pressure at 43 psi or so, then let it sit overnight, it should still be 43 in the morning?
Thanks.
Thread Starter
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From: Kailua-Kona, HI
Update:
So it may be a fuel issue based on my other thread. I think the new walbro might be no good. Intermittent issue. Seems like it is not priming on every cycle of the key. I charged the battery to make sure that isn't the issue, and am going to re-test tommorow.
ALSO: a friend of mine who owns a shop told me to tap into the pink wire going to my coil and to observe the voltage while someone os cranking it. He said that if I installed the IGN switch in the column just a hair off, it could be either cutting the power completely or to below 9 volts where things stop working properly if at all.
This sound accurate?
Could be a number of things, but it is just so strange how it tries to fire when you let off the key.
So it may be a fuel issue based on my other thread. I think the new walbro might be no good. Intermittent issue. Seems like it is not priming on every cycle of the key. I charged the battery to make sure that isn't the issue, and am going to re-test tommorow.
ALSO: a friend of mine who owns a shop told me to tap into the pink wire going to my coil and to observe the voltage while someone os cranking it. He said that if I installed the IGN switch in the column just a hair off, it could be either cutting the power completely or to below 9 volts where things stop working properly if at all.
This sound accurate?
Could be a number of things, but it is just so strange how it tries to fire when you let off the key.
Thread Starter
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Joined: Dec 2005
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From: Kailua-Kona, HI
Did some more testing today.
Starting fluid - no go, just a loud backfire.
Check fuel pressures for the um-teenth time. They are good.
Jumped prime connector and that also worked.
Just waiting for my girl to get home so I can test the IGN voltage while the car is being cranked over. Currently only 1/10th of a volt is being lost from the battery to the pink coil wire.
However, if my new IGN swith isnt lined up right that voltage could drop significantly or cut all the way out. Could be cutting the fuel pump out too.
Would the IAC valve cause something like this?
If my next test passes (cranking while measuring voltage to coil/fuel pump) then I'm going to post a link to a video on here so you guys can get a better feel for whats going on.
I really appreciate the help. Just need to get this thing running again!
Starting fluid - no go, just a loud backfire.
Check fuel pressures for the um-teenth time. They are good.
Jumped prime connector and that also worked.
Just waiting for my girl to get home so I can test the IGN voltage while the car is being cranked over. Currently only 1/10th of a volt is being lost from the battery to the pink coil wire.
However, if my new IGN swith isnt lined up right that voltage could drop significantly or cut all the way out. Could be cutting the fuel pump out too.
Would the IAC valve cause something like this?
If my next test passes (cranking while measuring voltage to coil/fuel pump) then I'm going to post a link to a video on here so you guys can get a better feel for whats going on.
I really appreciate the help. Just need to get this thing running again!
Thread Starter
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Joined: Dec 2005
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From: Kailua-Kona, HI
Seeing that you could smell a burning odor. I would first check the connector for the fuel pump under the driver side kick panel. Pull the relay off and look at the connectors. Second i would check all of the fusible links on the passenger side over the front wheel well.
