KYWes

Ok, this is wide open and a long shot but I'm hoping someone has a suggestion of something quirky to check.

My '95 Z28 is sitting at the body shop ready to be picked up.

It won't start. It turns over but it sounds like it isn't firing.

Recently replace the fuel pump and filter, it has gas, and it has been starting and running fine.

This is an intermittent problem. It did it to me a couple of weeks ago but after cranking a few times it fired up and ran good.

It happened one other time at the body shop. They waited and tried again in a few hours and it fired up.

Then Sat. when I went to get it it wouldn't fire. I checked ignition wires and anything else easy to see but no go.

I'm going over this afternoon to try again and if it doesn't start I'll have it towed home and dig into the problem.

I realize it could be a hundred different things but hoping for a quick thing to check.

94Z28LS1toLT1

Sounds like it can be ur icm,or opti but I'd check those two.

Mike 94 Chevy camaro z28 m6 stock

Fatdog2

This sounds crazy but I've read this before and what the person did is he took a rubber mallet and tapped on the gas tank a couple of times(not hard) and and the car started.Hope this helps.

Fatdog2

I would not use a metal hammer as sparks can fly.

KYWes

As a follow up I went to the body shop yesterday to get the car. It took a bunch of times cranking and we eventually had to put a jump box on the battery but then it fired up. It ran good on the way home. When I got home I shut it off and it cranked right up.

parkers Z28

Do you have a way to check for codes....there is a free scan software on here if you don't......can you hear the fuel pump prime when you turn the key ???

Injuneer

He has Scan9495.... I've reviewed a data log. Thought about that when I saw the first post. Also believe he traced a similar problem last year to the fuel pump and replaced it. Had very good dyno results recently.

KYWes

Update of a sorts - It's very cold here in Louisville. I'm waiting for it to warm up than I'll check codes, etc. I Appreciate the interest and suggestions.

KYWes

OK, I read the codes and I had a 21 and 42. I also had an air flow reading(?) of 480 that didn't vary. I suspected a problem with the MAF sensor.

Upon checking I found the brown wire on the MAF sensor had been pulled loose. I suspect this happened when the body shop mechanic insisted on helping me.

I reconnected the wire, and cleared the codes.

Car is starting now (car started fine with the brown wire disconnected) and running good. Air flow numbers are much lower and variable.

If the car doesn't start again I'll check the codes and see what I can find but right now it's starting and running fine with no codes.

Question: When I first got the car home, I charged my battery overnight because it had gotten run down from all the cranking. My battery charger gave an error code saying there is a problem with a bad cell in my battery. As I said it's starting now and the problem was never with turning the engine over.

However, I've wondered if there is a minimum voltage for the computer to operate correctly. Could the voltage get low enough to cause a computer or other sensor problem but allow the car to crank?

Injuneer

If voltage to the PCM is too low, it sets a code. I think it sets somewhere between 8.5 - 9.0 volts.

480 gps on the MAF circuit is an open signal circuit. That should have set DTC 48. If the MAF fails, the PCM defaults to the speed-density method to calculate the mass air flow, using IAT, MAP, RPM and VE (volumetric efficiency). VE is read from a programmed table, and that table needs to be altered when any changes are made that affect engine breathing. Maybe that table hasn't been updated for you modifications.

DTC 42 is for the signal to the ICM. That will shut the engine down and make it hard to start. That's the one you need to track down.

DTC 21 indicates at some point the TPS volts exceeded 4.9 volts. That could indicate an intermittent short in the harness connector or sensor.