fuel injector harness power distribution

[chris c]

from what i understand, the injector harness is powered by a wire which comes through a 8 pin connector. the injector harness 8 pin connector sends power through pin A

that wire connects to the engine harness and goes back to the firewall connector at pin C4 i believe. [this is coming from memory].

with the ignition on, i have no power at pin A on the 8 pin connector which is part of the injector harness. if i disconnect the connector off the firewall, pin C4 has power.

is this as simple as a bad wire connecting the power distribution block to the injector harness or do other sensors feed back to the PCM and the readings of those sensors can be killing power to the injector harness?

[Mechanical Mike]

Make sure that the pink injector wires have 12 volts with the key on. Check between the pink wire & the negative battery terminal.
The PCM grounds the injectors through the black wire which completes the circuit & fires the injector.

If you have 12 volts at the pink wire but no injector pulse then you know that the PCM isn't grounding the injectors. This can be caused by a faulty throttle position sensor putting the PCM into 'clear flood mode'. The PCM on the 94 & 95's are the most troublesome, this could also be the problem.

[chris c]

Hi Mike. I have 12 on the pink, H on the 8 pin connector.

Ignition control out from ICM is a white wire. This also seems to tie into the 8 pin connector, ICM and PCM. I can install a new TPS but I feel like I am just throwing parts at it now. I did test the TPS too.

It appears only PCM and TPS can abort injector pulse if wiring is OK?

[Mechanical Mike]

You can unplug the TPS to rule rule that out. Also try starting with the cam sensor unplugged.
The other required input would be the crank signal & I'm not 100% sure but think you can rule that out if you have spark.

[chris c]

i am 100% sure the injectors are not firing. fuel pressure is adequate, spark is there...

i tried starting w/o TPS and no dice. i keep coming back to this white wire which is terminal A on the 8 pin. i'll toss a TPS in tonight just to see.

thanks for all the help...

[Mechanical Mike]

I wouldn't spend the money on a TPS it'll only kill the injectors if it's returning 4 -5 volts to the PCM. Unplugging it was enough to rule it out. Consider getting a PCM from the junkyard. The yards around here will take them back if it doesn't solve the problem. Although some will only give you credit towards another puchase.

[chris c]

completely stumped...

no start at all now. with the key on each injector has power at one of the terminals on the harness, but will not flash a 194 bulb when cranking.

i have tried with the TPS disconnected, same result.

i checked the ground for the PCM, i replaced the PCM, i checked the grounds for the ICM, i replaced the ICM.

tomorrow i will trace the ground wire back on the injector harness...

what else can cause this? does the VATS disable the injectors?

[Mechanical Mike]

The typical problem with VATS is the module isn't able to read the resistance of the pellet in the key. This is usually caused by a problem with the lock cylinder contacts or the wiring between the VATS module & lock cylinder. When this happens the security light will flash when the key is turned to run & both the starter & the fuel injectors will be disabled. If someone bypassed the starter relay then the starter would work but the fuel injectors still wouldn't pulse & the security light will still flash.

I suppose a faulty VATS module could allow the starter to work but not send the signal to the PCM that allows the injectors to pulse.

[chris c]

so if the security light is flashingwhen thekey is 'on' or crankingi may have a vats issue?

what is the normal behavior of the vats/ security lamp?

thanks for all the help on this...

[Mechanical Mike]

Normally when the key is turned to run & the doors are closed the Security light will come on for a few seconds & then go out.

Yes, if the security light is flashing you may have a VATS issue but the starter shouldn't be working.

[chris c]

Security lamp stays on solid with key in on position. Car actually started and security light stayed on.

So puzzled