89' 4.3 tbi starting/fuel problem???

[ih69l]

Hi everyone, I'm not good with the tbi at all, I'm really hoping someone has a solution for me. I have a 89 s-10 4.3 tbi. The only way it will start is if you mess with the gas pedal. I can crank it forever and it wont start but if I floor it and let off it starts and runs fine. When I turn the key on or crank it over, the fuel pump wont come on, but when it does start I can hear the pump for a few seconds after I shut it off. I did a full tune up including fuel filter. I took the fuel lines off the throttle body, cranked it and the only way gas will come out is if I floor the pedal. Sorry for the long post I'm just hoping the more info given, the better the reply I might get. Thanks alot in advance.

[blazes9395]

Welcome to AF!

If the pump does not come on while you turn the key to the on position, there is an issue right there. The pump must prime at that point for the engine to start. The first thing I would do is locate the test wire for the fuel pump under the hood, and manually start the pump by jumping it at this point. The wire is usually located at the back of the engine, on the firewall, about over the distributor. If the pump starts without a problem and engine starts without you pressing the pedal, you have some sort of electrical problem. If the pump does not start after you manually jump it, then your problem lies with the fuel pump and/or its connections.

[ih69l]

Does the oil pressure sending unit have anything to do with the fuel pump run time? When I turn the key on, the oil pressure guage tops out. Maybe nothing to do with the problem, just thought I would throw it out there in case.

[MT-2500]

Originally Posted by ih69l

Does the oil pressure sending unit have anything to do with the fuel pump run time? When I turn the key on, the oil pressure guage tops out. Maybe nothing to do with the problem, just thought I would throw it out there in case.

No on oil pressure switch.
It only feeds back up power to pump in case the fuel pump relay fails.
Run the test as blazes9395 instructed.

Also check TPS sensor voltage sensor real close.
Bad reading TPS can shut fuel injectors off.
Like in the clear flood mode.

[ih69l]

O.K., I jumped the test wire and the pump runs fine. Like I said, when I floor it while cranking it will start and when I shut it off, I can hear the pump running for a few seconds after shut off, then if I restart it, it will start right up. How do I check the tps, and what should the voltage be? Does it seem like the tps might cause this? Thanks for the help so far.

[MT-2500]

Originally Posted by ih69l

O.K., I jumped the test wire and the pump runs fine. Like I said, when I floor it while cranking it will start and when I shut it off, I can hear the pump running for a few seconds after shut off, then if I restart it, it will start right up. How do I check the tps, and what should the voltage be? Does it seem like the tps might cause this? Thanks for the help so far.

Check with volt meter or scanner tps reading.

Idle should .5 -1.0 volt
And increese to 4.5 volts wide open without no drop outs.

[ih69l]

Mt-2500, which wire plugged into the tps do I run the test on?

[MT-2500]

Originally Posted by ih69l

Mt-2500, which wire plugged into the tps do I run the test on?

Check black for good ground.

Check gray wire for refernce voltage of 4.5 to 5.0 volts.

Check dark blue wire tps sensor voltage into pcm.
.5 to 1 volt idle and 4.5 tp 5 volts wide open throttle.

And with a scanner read out tps sensor voltage to pcm.