Stockdale Dave

Hey folks. Just picked up a 90 model C1500 with a 4.3. Truck has sat for around 12 years. Pulled the bed and replaced the gas tank, fuel pump, and filter. Pump runs and I am getting gas to the throttle body. Turns over but won't start. Put gas down the TBI and it runs like a champ. So I am getting good spark. I shorted the A and B terminal on the link plug but instead of turning on the service engine soon it turns on the up shift indicator light. Visual inspection of wiring harness looks good. Looking for ideas. Thanks in advance.

Dave

tech2

throttle body injection? no fuel out the injectors... if yes....check for power at the injector wires with key on.

Stockdale Dave

Thanks for the reply. If I go across the A and B lead of each injector connector I get zero volts. If I go from the A lead of each connector to battery ground I get 12V. Should 12V be present all times the key is on?

Dave

tech2

yes.
one wire should have battery voltage with key on. the other wire the pcm grds to open the injector.
take a test light that uses a conventional bulb connected to battery voltage (or use a noid light with the same resistance as the injector). crank the motor and the grd side should flash...if it doesn't you have no injector pluse.

Stockdale Dave

Test light on 12V positive battery terminal. Inserted into B connector. Both connectors flash as the engine turns over so it looks like it is receiving the signal pulse.

Dave

Stockdale Dave

Beginning to wonder if the gas is not making it through the pressure regulator. If I pull the injectors from the throttle body and crank the engine should I see fuel going to where the injectors should be?

tech2

I've never had one apart but seems logical.

Stockdale Dave

Will get back on this Thursday. Still open to other ideas guys.

Dave

Gumby22

You stated in an earlier post that you’re getting fuel to the throttle body, and you’re getting injector pulse while cranking, so the most likely issue is the injectors are dead or severely gummed up from sitting for so long. The body and regulator are probably just as nasty.

In terms of fuel flow, the FPR is downstream of the injectors, so to have flow to the TB means flow to the injectors. That leaves the injectors and/or blocked flow inside the injector body.

SMP and a couple other companies make FPR & gasket service kits for them. There’s also new or reman injectors available. It’s not a difficult process to take them apart and clean them, but the body has to be removed from the TB to get the FPR out. You’ll need to remove the supply and return lines as well as the mounting screws to remove the injector body from the TB.

Test the injectors by providing direct power and ground from the battery with a 20A fused jumper. If the fuse blows or you don’t hear/feel the injector “thump” when doing this, consider them dead. If you do hear/feel anything, even if it’s very faint, you can probably clean them.

Stockdale Dave

Thanks for the reply. I hadn't figured the FPR was downstream of the injectors. I have found a throttle body rebuilt kit from Standard Ignition I believe for around $30.00. Going to try to clean and rebuild throttle body, replace FPR, and 2 rebuilt injectors and go from there. Will update if this solves the issue.

Dave