85 Chevy k10

gen 3 5.3, Evap deleted, DBC

ebay harness, for ‘5.3 4l60’

lano tech in tank fuel pump, 6 AN lines, 58 psi prime, 55 psi cranking.

VATs deleted, PRNDL enabled but grounded in cab. PCM grounded to cab and block, rad support grounded to frame, battery grounded to block.

starts, half *** idles for a few seconds, quits, won’t start again.

IC and injector wires are pinned correctly at PCM. Injectors are pulsing, getting throttle % on HP, getting a MAP reading, temp sensors are plugged in.

engine was running with the PCM I have in a different vehicle, but this is a new harness. When it fires up it sounds like all 8, and no misfires. Cam and MAP sensors are in correct places. It’s something dumb that’s making the PCM unhappy, just need to figure out what

 

VATS disabled-tuned out, FOR SURE??

 

Even tried 2 PCMs both disabled

 

I know you said 55PSI cranking, but what happens after it fires up? Does it drop like the signal to the pump is getting shut off?

 

I can check but I don’t believe so. When it fires the first time it’s all 8 then it chugs trying to idle and can’t get it together. I unplugged TPS and AIT for 30 seconds plugged them back in and that’s when it fired and actually gave me a good idle for a couple seconds and then quit. Then try starting again and just whirls over and fires at a couple cylinders. But I can check for injector pulse after that first fire I guess and see if PCM is still telling it to give juice

 

I'm more concerned that the PCM is telling the pump to shut off, which is why I wanted to know if it was dropping pressure during the short time it's running.

 

As GameTech once so wisely advised me around here, check that you don't have your O2 sensor wiring swapped to the wrong sides.

Rick

 

Pulled MAP tried in a different truck and worked, grounds I double checked along with cranking fuel pump voltage. Ran on starting fluid. So that tells me it’s not timing, not spark. Have good pressure. One thing I did find is AIC valve popped out and can’t seem to get it to stay in place, when it’s not in place i get nothing on injector signal. When it’s half assed set in there I get my signal but doesn’t seem consistent. So I’m going to try this. Also PCM came out of a jeep with a 4l60, PRNDL is enabled, I wouldn’t think it would cause this to tell injectors to quit?

 

If the neutral safety is hooked up, it shouldn't allow the engine to even crank. I don't see how it would crank and then somehow disengage the neutral safety. And I don't believe that would disengage the injectors/coils anyway. What is the AIC valve? Do you mean Idle Air Control? If you have a vacuum leak, it would definitely cause running issues if the air is unmetered.

 

I have found the Culprit, the classic plugged injectors.

 

That'll do it, thanks for returning to give an update. Threads like this will help people in the future.