Helping a friend out with an 88 350 TPI. A couple of months ago, it ran (with a slight plug wire issue). The wire issue was corrected and now, will not start.

The fuel pump is new and 46psi at prime (key on).
The fuel pump will run during crank.
The ignition module and coil have been switched with known good ones.
Engine will fire with starting fluid and die as soon as fluid is spent.

The injectors will pulse/ fuel pump runs when applying brief +12v to ppl (ref) wire on 4wire connector of module plug. Injectors all pulse testing manually as well.

Injector wiring is good.

Key off, applying +12v to the hot side of injector wiring causes fuel pump relay to switch and run pump.

Injector ground is closed with ECM keyed off, open key on.

No injectors connected, test light to injector ground (ecm side) and other +12v battery, there is no (light) pulse during crank.

Key off, test light is on (as connected above), key on, test light out.

Does this sound as if the ECM injector driver is toast ?
I took apart the ECM and I didn't smell any released blue smoke and see nothing physically fried ?

I'm at a loss and would appreciate another opinion before suggesting replacing the ECM.

I'm sure I missed a detail or, two but, thanks for any input anyone may have.

 

Is it a VATS car? I know officially 1989 was the starting year of VATS, but I'm assuming like everything else, a few early cars were released late in 1988, thus having a 1988 date but also having VATS. It was just a thought.

 

No VATS, the engine cranks as is supposed to. Everything does what it should except the injectors.

 

The test light really won't tell you what is going on at the injectors. Get a set of Noid Lights and check that the injectors pulse when cranking. Auto Zone and others have these sets to Loan for free (just pay a refundable deposit). If the injectors pulse when cranking or when "tickling" the purple wire at the distributor with 12V, the injector driver is good. If you have a cranking pulse at the injectors, then inject some starting fluid and see if the injector pulse continues when the engine starts. I believe that the fuel pump will run on the oil pressure switch as well as the ECM command. If the Trigger pulse from the distributor is not present or the wiring is open, then the ECM will not command the pump to run, but the pump will start when the Oil pressure switch closes. Without the reference signal from the ICM, the injectors will not pulse, even though the pump is running. I am thinking that you are loosing power to the ECM with the key in the "run" position or a Bad TPS. If the TPS is telling the ECM that the throttle is Wide open when cranking, this is the clear flood mode and the injectors are deactivated but the pump continues to run. Check the ECM Ignition fuse as well.

 

I know test lights suck for the purpose of injector testing but, it was the only available option last night (aside from a DMM).

They seem to not pulse during crank (stethoscope test, not 100% accurate too, I know) but, will when 'pulsing' the purple wire at the dist. Doing so also cause the pump to trigger momentarily.

It will run briefly on starting fluid or, if you manually pulse the injectors to dump some gas into the engine. It will not stay running once that amount has burned out though.

There is no oil pressure switch on this particular vehicle.

I was thinking the ICM may have taken a crap as well though, it was still triggering the coil. I swapped it for the GM unit from my MSD with no change in starting condition.

I have run through the fuses and links (but not tested @ ECM) and are good. The TPS is set at .58v. Which is +.04 above 'stock', I believe.

I will have to check power at the ECM tonight or, tomorrow.

The strange part is, the engine would start and run perfectly fine the last time (about 2 months) it was ran. There was a plug wire arcing badly against the header so, it sat until some new wires were ordered. Plug wire (just the bad one for now) fixed and the pump 'died'. That's when I got a call from my bud.
It was simply a bad contact at the sending unit. That solved, some fresh gas, turn the key... cranks, no start.

Nothing else was touched or, changed in the two months it sat idle. It just decided, it wasn't going to run anymore.

Should the injectors be grounded through the ECM while the key is off ?
The ground opens as soon as the key is on.

I've tried to check everything i can think of and run though my Helm's trouble charts. I can't imagine why the ECM would just take a crap out of nowhere but, at the same time, it's the only thing that seems to not be doing what it should.

Just a note too, the ECM is a reman, the original ECM took a dive many moons back.

It's long winded, I know. I'll see about 'renting' those lights from AZ as well. Thanks again.

 

It was the ECM. Replaced, turned key and it fired up immediately.