No Check engine light at anytime? 1995 C10 5.7 the check engine light does not work.

dexter551 · May 29, 2024

1995 C10 5.7 check engine light does not work. Cranks but no pulse to injectors will run with fuel added to tbi for a few seconds.
I pulled the bulb from the dash it was good
Check engine light does not work all other warning lights on dash work when key is turned
Replaced distributor and ECM from a running vehicle
Throttle position sensor changed
checked all grounds nothing broken
Fuel pump relay was making a weird noise jumped across pins can hear pump running replaced relay from running vehicle
ignition switch to harness under dash just replaced did not help
Oil pressure gauge works during cranking can see pressure build
noid light at fuel injectors has no pulse
9v battery across injectors can hear the click

Any advice on what to look for now?

Schurkey · May 29, 2024

dexter551 said:
1995 C10 5.7

C10? Not C1500?

dexter551 said:
check engine light does not work.

Download the service manual set for your vehicle from the links in the Sticky thread section of the Engine forum.

Follow the schematics, trace the wires and inspect the instrument cluster for faults. Could be an ECM fault, but you've already replaced that.

dexter551 said:
Cranks but no pulse to injectors will run with fuel added to tbi for a few seconds.

Verify ALL fuses. Make sure the injectors have power when the key is in the "On" or "Crank" positions. The computer supplies ground to fire the injectors.

The ignition system is working well enough to provide spark to the spark plugs.

dexter551 said:
I pulled the bulb from the dash it was good

Are you SURE the bulb is good?

dexter551 said:
Fuel pump relay was making a weird noise jumped across pins can hear pump running replaced relay from running vehicle

Did that fix the "weird noise"?

dexter551 said:
noid light at fuel injectors has no pulse
9v battery across injectors can hear the click

Either you have no power to the injectors, (fuse, or broken wire/poor connection in the harness) or you have no ground for the injectors (broken wire/poor connection, or failed ECM.)

You've already replaced the ECM. Unlikely but possible that you have two failed ECMs. Engine runs if you supply fuel, so the ignition system seems to work.

Pretty-much leaves a broken wire in the harness; or something really weird.

dexter551 · May 29, 2024

C1500 verified bulb was good, 12 volt power to injectors with meter Fuel pump relay does not work with key tried three relays which worked on running vehicle have 12 volt power at pins for relay can jumper pins and hear fuel pump running 12.84 volts to coil with key on same to wire leaving coil to distributor.

sntrym · May 29, 2024

Clogged fuel tank pickup or fuel filter? Have you verified fuel is making it to the throttle body?

Chevyman1969 · May 29, 2024

If you were able to get it to start by pouring fuel down the throttle body I would say you need to check your fuel pressure with a gauge. I see you replacing a fuel pump

GoToGuy · May 29, 2024

You only mentioned weird fuel pump noise, replaced relay times 3. Runs with fuel dump. Think what's that tell you? Fuel system isolated problem . Fuel flow, ? fuel pressure ? Weird fuel noise? , failing pump, low voltage, bad ground.

Schurkey · May 29, 2024

dexter551 said:
noid light at fuel injectors has no pulse

Does the noid light work? If your test equipment is faulty, you'll waste a lot of diagnostic time. I ask because I bought a noid light for TBI, and it lasted about three months.

IF the fuel pump doesn't prime, you've probably got no fuel pressure until the oil pressure builds during cranking. Need to track down that problem.

dexter551 · May 29, 2024

It seems like it would be more of an electrical problem as the check engine light never comes on when turn the key on. I really don't understand how a fuel pump problem would cause a no pulse no check engine light trouble. I did check the noid light it is verified good, I also checked the fuel injectors with a battery and they do work

Schurkey · May 29, 2024

I think you have more than one problem. It's not that the fuel pump problem is causing the injector problem and MIL problem.

MAYBE they all tie back to the ECM--as in the ECM is causing all three faults.

dexter551 · May 30, 2024

Yeah i found the service guide and the wiring diagram looks like it's going to be a pain

No Check engine light at anytime? 1995 C10 5.7 the check engine light does not work.

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