No fuel

[Bigdaddyjak]

1987 Chevy 1/2 ton 4x4 , 305 tbi. Feul pump went, replaced it. Now I can hear it , no feul coming out of injectors . I’m only getting 6volts at tank . I changed they relay and OPS. No change . Gonna pull the tank again and start tracing it back from there . Any suggestions? Thanks .

 

[Frankenchevy]

The relay and sender well grounded?

 

[1987 GMC Jimmy]

I’d backtrack a step and check the voltage at the test lead right there by the relay. If you’re seeing the same thing there, I think you’d be wasting your time to trace wires. Is your SES light coming on when you turn the key on?

 

[Bigdaddyjak]

When I turn the key once the seatbelt light comes on, when I turn all the way to engage starter the break light on dash lights up , (these 2 lights are next to each other) I don’t think SES, is coming on . I will have to look n c where that one is . I didn’t check the voltage at test port at relay, I did put 12 volts from battery there just to hear the pump run . But I will check the voltage there .

 

[1987 GMC Jimmy]

Okay, when you turn the key, “Fasten Belts” should come on red and “Service Engine Soon” should come on orange. Either the bulb is burnt out or there’s some kind of ECM problem. While it wouldn’t be too laborious to check your fuel voltage at the test lead, I would make the SES light my top priority. You can either swap in a known good or new 168/194 bulb or try unplugging the ECM to see if the light comes on when you turn the key then.

 

[Bigdaddyjak]

87 gmc, I will try it and c . I forgot to mention . Truck will fire up if I put feul in the tbi, so it’s not a spark issue, it is feul delivery somewhere . Thanks !

 

[Bigdaddyjak]

When i got this truck the PO, was a hack ! Installed a system !! So it has a stereo with sub and box behind seat , and mist of the dash lights and gauges didn’t don’t work. I have the feul gauge, speedo and oil pressure were working , but the lights weren’t . The break warning and seat belt warning lights do come on when staring . I don’t recall if the SES, light worked or not, I’m trying to get my fingers in to change bulbs now .

 

[Bigdaddyjak]

So I couldn’t get my fat fingers in to change the bulb, but I got some pressure on it and it lit up, the 4x4 didn’t, but I didn’t mess with it

 

[chengny]

1987 Chevy 1/2 ton 4x4 , 305 tbi. Feul pump went, replaced it. Now I can hear it , no feul coming out of injectors . I’m only getting 6volts at tank . I changed they relay and OPS. No change . Gonna pull the tank again and start tracing it back from there . Any suggestions? Thanks .

The fact that you are seeing (reduced) voltage at the pump would point to a problem in the power supply circuit - rather than in the control circuit. There are two paths that can supply voltage from the fuse block to the pump (through the OPS or the FPR).

The FPR is controlled by the ECM - which needs to see a distributor reference pulse before it will pull the FPR in.

On the other hand, the OPS is hydraulically operated and entirely independent of the ECM. It provides an auxiliary power supply to the pump in case of an FPR failure. The only requirement to close the contacts is that engine oil pressure be at least 4 psi. That 4 psi is easily developed when cranking the engine.

So, for the problem to exist in the control circuitry, it would mean that both the relay and the switch would have to have failed. You'd have to be really unlucky for that to be the case. On top of that , even after both the OPS & FPR were renewed, an undervoltage condition at the pump still exists.

I didn’t check the voltage at test port at relay, I did put 12 volts from battery there just to hear the pump run . But I will check the voltage there .

If you get power at the pump - and it runs - when 12V is supplied through the test port, you can forget about checking everything between the FPR/OPS and pump (TAN/WHT 120). And checking for voltage at the test port won't show anything. The only time that terminal is hot is if the FPR has failed and isn't pulling in (contacts open through FPR and closed to test port) and the engine is being cranked (to develop 4 psi) and current is flowing through the OPS.

I would concentrate on the line sides of the OPS/FPR. That is the ORN 440 circuit. It runs from the fuse block to the OPS/FPR and is fed from the 10A ECM B fuse. The voltage drop is most likely happening in that part of the circuit.

Description of fuel control circuit and diagnostic chart:

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Normal - current flow both the relay and OPS:

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Failed FPR - oil pressure established by cranking (the only time test port will show voltage):

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More detailed dwg:

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[Bigdaddyjak]

Thanks chengny, I will look thru the info, and take it from there , c what I can chase down .

 

[Charlie]

 

[Bigdaddyjak]

Ok, I’m slightly confusing myself, but I will get there ! Thanks for all the info !

 

[Bean]

1987 Chevy 1/2 ton 4x4 , 305 tbi. Feul pump went, replaced it. Now I can hear it , no feul coming out of injectors . I’m only getting 6volts at tank . I changed they relay and OPS. No change . Gonna pull the tank again and start tracing it back from there . Any suggestions? Thanks .

 

[Bean]

Take the fuel filter off an try to start it an see if an gas is coming out of it , or your line is dirty from the filter to the tbi . Injectors could be stopped up !

 

[Bigdaddyjak]

It’s hard to get much done during the week, so I’m studying the diagrams, thanks for input guys !