Low Voltage At Fuel Pump

[sls639]

Hey guys, new here, did a little search and didn't see anything specific on this topic.

Picked up a '93 Burb a few month ago, and after having the radiator rebuilt, it has been running great.

Went home after work two days ago, left again for class, stopped a Starbucks, and she wouldn't start. Good crank, but no start. Thought it was out of gas. Wife took me to class, came back 2 hours later, dropped in a few gallons and she fired up. Drove to the station and dropped in $30 of gas, and no start again.

Opened her up and cranked, and I'm not getting fuel to the TBI. Removed filter (filter is clean) scabbed in a spare fuel pump and hobbled it home.

Checked voltage at grey wire to the pump (along frame rail) and I'm getting about 4 volts. Checked voltage at grey wire coming out of the fuel pump relay, and I'm getting full batt voltage there. Suspected the Fuel Pump Oil Pressure Switch, changed that out, no start.

I don't know if i want to share this because I don't want every one to jump to "oil pump", But I did notice a valve tick I've never heard before.

Since it has sat in the driveway, it has intermittently started twice. (pause) I just went out and re-did the test, started fine ran it for a few minutes, shut her down and no start.

I know that the "Fuel Pump Oil Pressure Switch" will shut down the pump if pressure drops below 5 psi, and I have no gauge, but wouldn't I get an idiot light if the pressure was that low?

Googled this prob and found others with the same voltage prob, but no solution was ever posted.

Any help will be greatly appreciated, thanks in advance,

Chuck.

P.S. I'm to the point of "hotwiring" the pump in after the rely to get her back on the road.

[98trck]

sounds simple and i imagine it has been done

did you check of the both ends of ground wire from the pump

it sounds like you have a good connection at the relay

[sls639]

No, I haven't. I tried to get my hands up on top of the tank to feel around for a connector of any kind, but the Burb is a little tight up there. Definitely cant see up there. I've done a lot of wrenchin' in my days, but I'm no electrical genius. Seems to me that even with a bad ground, the supply wire (grey wire to the pump) should still read 12 volts? Am I wrong? I pushed a needle into the wire about 3 feet back from the tank and connected a multimeter to that, turned the key and got 4 volts for 2 seconds them zero. Same at the relay, pushed a needle into the grey wire just on the "out" side of the relay, tested there and got full voltage for 2 seconds.

I'll check ground straps today. And I'll see if I can find the oil pressure gauge i have laying around to see if i can hook it up to the engine. Can I put it where the Elec oil pressure sender is temporarily? or will this mess with the ECM and cause a no start?

BTW I can't find the Fuel Pump Test/Prime connector that is supposed to be in the engine compartment on the drivers side.

As i said the prob is intermittent, and when it does start, it seems to run fine. Not starving for fuel or any hesitation. Which leads me to think the pump is still good?

I'm no expert on pulling codes, but I jumped the OBD connector and counted a 2 - 1 three times, and a 1 - 2 three times, no other flashes.