Fuel system issue

[wolf1477]

'93 S10 4WD 4 door Vortec V6 Blazer.

Ok, so after replacing my fuel pump/sending unit, relays and checking fuses...I have absolutely no power going to the pump (Checked at sending unit plug...nothing going to the back of the truck).

Is there a secondary fuse box I'm not seeing somewhere? Another relay? I'm stumped and already irritated that I spent the $$ getting the fuel pump and sending unit when it looks like I didn't need to in the first place.

Any help would be appreciated.

[jsgold]

I do not know of any additional fuses for these. i also have a 93 and the service manual says that a faulty oil pressure switch can cause problems on this. The pump also only has power on it for 2 sec. unless started. Might try the oil pressure switch, it controls the fuel pump too, according to this book.

[wolf1477]

Hmmm, interesting...I'll check on that. Also a new update: Talked to a mechanic friend of mine and he said there's a reset button for the fuel pump (somewhere in the cab area?) that's designed to shut the pump off in case of a collision, but, can just turn it off occasionally. Any ideas on where this mystery button would be?

[wolf1477]

Heh ok, stupid question: Where's the oil pressure switch on this thing? I can't find my manual and am not looking forward to spending another day playing in the rain to find it. I'm guessing lower passenger side of the block?

Also, any thoughts on that reset? I'm getting mroe and more stumped the more I sit here thinking about it.

Thanks again

[jsgold]

The oil pressure switch is in a terrible place, near your distributor, on back side of engine... I do not see anything like a cut off switch in my truck or in my GM service manuals, but still looking.

[MT-2500]

You should have a fuel pump prime wire. A single gray wire with a plastic plug on the end hanging around there not hooked to anything. It may be near relay.
It is connectet to the fuel pump feed gray wire.
Hook a 12 volt fused jumper to it and see if fuel pump runs. It should have 12 volts on it for the 30 second fuel pump prime or after the engine picks up oil pressure.
And have 12 volts on it when the fuel pump relay turns on.
Check at fuel pump relay for 12 volts on orange pin D
Check pin c black and white for ground.
check pin a dark green/white for pcm control that turns on relay.
And pin B will be the gray wire to fuel pump
There is no shut off switch on it But the relay is fused and also oil pressure switch may be fused.
Get a 12 volt jumper on the gray prime wire or jump the pin B gray fuel pump wire at fuel pump relay.
Fuel pump should run. If not go back and check at fuel pump plug at the fuel tank for voltage.
MT-2500

[MT-2500]

Also check and make sure the engine is getting fire to the spark plugs.
If the ign system or pcm is not firing up you will not get a signal to turn on fuel pump or relay.
A not on the oil pressure switch it only provides power to the fuel pump while it has oil pressure to keep engine running in case the fuel pump relay quits.
Mt-2500

[wolf1477]

K thanks a lot, ya'll have given me plenty to think on.

I miss my carbureted engines! At least they made sense (not to mention fuel pump didn't require a tank drop)

Thanks again