I have a 95 Z28 here that I cannot get an injector pulse on. It will not start because of this, but I have been able to get it to start by squirting some fuel into the intake.

I have made sure that both grounds coming from back of PCM for the injectors are good. (Black/ White) and (Tan/White). I also read about checking the Purple/White wire.

I checked this wire at the connector spot near the passenger side valve cover. I probed both sides and found 5 volts. I tried this several times and got readings in the Millivolt range other times. I'm assuming when it hits 5 V its sending the signal to fire (must be TDC)?

I also checked this signal at the PCM and found same readings in the millivolts.

I manually jumped from before that connector to the PCM (purple / white) to see if there was a break in between, but that was not it.

I manually grounded the other ground wire (forget the color) at that connector, and that did not do it either.


Also please note I have switched the PCM for a known good one and that did not cure it. I also replaced the opti and coil/ignition module.

Any other ideas guys? What can I do next?

Thanks,
Bob

 

Are the injectors getting power?
The ppl/wht wire is reference wire that is a 5 volt square wave the pcm uses to determain rpm.
Can you scan the PCM's data stream?
What is the TPS volts at key on engine off?
Can you hear the fuel pump run?

 

TPS at Key on is .42V

Fuel pump does trigger when key goes on, fuel pressure goes to about 40 psi. Yes, I can scan the data stream but get nothing abnormal, no codes, etc...

The injectors do have 12 volts to them.

 

Doubt your injectors are the problem. They require either an O-scope or test lights made specially for testing injector pulses. What's your fuel pressure at cranking?

Any history to this problem?

 

I have verified that the injectors are not firing because I have shot fuel directly into the intake and the car started, (tried to). I also own a set of NOID lights that clip into the injector clip and show a blinking action as they trigger. They are showing me no lights except for when I first crank over, I get just the one faint blink and thats it.



History of the problem is as follows: Owner (friend) had another person install new ported heads and cam. He got car back and ran for the drive home, then stalled in a parking lot. He was babying it for the drive home (break in). It stalled then would not start.

I verified good spark, then shot fuel into the intake manually and the car tried to fire. So, I know its without fuel. Pressure is 40 psi. Fuel pump primes well.

 

Ok we did not know you had the test lights for injector pulses. That's a start. Any codes? Remember that some codes like 41 and 42(just an example) shut the injectors off and do not set the SES light.

 

no codes...

 

Try checking the injector fuses and then resetting the pcm.

 

all fuses good, and i have replaceda or reset pcm. Thanks though.