help to diagnose a fuel pump problem?

[northmansx]

Hello everyone, i have a 93 sub with a 350 in it. I believe i have a fuel pump problem and would like to know for sure before i start buying parts.

I cannot hear the fuel pump running, and i have placed a white shop towel in the throttle body and it remains dry when i turn the engine over.

Any tips on where to look for sure to know it's the pump? What about fuel pressure, what specs and how to test?

What about the relay, i have tried another one, but it wasn't for my exact model? I have also checked the fuse and it is fine too.

Sure could use some advice as summer holidays are on the way and the old silverado just won't cut it. Thanks guys...

I just remembered that when i pour fuel in the throttle body it will start and run til that fuel is gone.


Northmansx

[rdharley3]

My 99 tahoe did the same exact thing it was the fuel pump.

RDH

[gbic1]

if you can get to the connector and check for 12 v while cranking. If you have the 12 v and no pump noise then pump is bad. They go bad a lot!

[renville]

buy the chilton manual for your truck. the diagnostics tests for the fuel pump are spelled out very clearly in it.

basically you should have 12V at the pump as soon as the key comes on. you need a test light or volt meter at the plug going in to the pump. unplug the pump and plug in the test light or meter.
this 12V line is also fused so it could be as simple as a blown fuse. The fuel pump should run for approx 5 seconds when the key is turned on then stop.

[northmansx]

Is it possible to check for 12v with the tank in place? Also what color wire is hot? Where is the fuse located in the fuel pump wire? thanks guys

[renville]

Originally Posted by northmansx

Is it possible to check for 12v with the tank in place? Also what color wire is hot? Where is the fuse located in the fuel pump wire? thanks guys

typically all 12V wires are red. you can get a test light for about $5 at the store. one end is a clamp that you hood to ground. the other end is a sharp pointy end you can pierce the insulation of the fuel pump wire. you can test the wire where it comes off the frame going up to the pump by hooking the clamp to ground and then pushing the other end through the insulation. have someone turn the key on and the test light should light up.

the fuse should be under the dash with the other fuses. look at the silkscreen on the cover that tells where they are located. a quick tip with fuses. you can hook your test light to ground and then use the tip to touch the back of the fuse. touch both sides of the fuse. it should light up on both sides if the key is on. if one side lights up and the other does not pull the fuse and you'll find its burnt out. if the fuse is bad then your probably pulling too much current so the pump is going bad.

[johnnybexperienced]

I have had to replace my fuel pump on my 99 burb Twice. If you are not hearing it, then it's toasted. My replacements only lasted for a year so get one with a warranty. It sux to do it Twice.