Loud Fuel Pump.

jsoden · June 4, 2011

My fuel pump has been considerably louder lately. I've already ordered the unit to replace it in the tank. (Going to do that next week) This morning, I woke up and my battery was completely dead. I had not left anything on to drain it. It barely registered 3 volts on my meter. I replaced the battery and it's running good again. However,,,, my fuel pump is now quiet! I let it run for over a half hour today in 90+ degree heat and nothing! I didn't add any gasoline or do anything else to it. My question is,, can a dying battery kick out higher voltage and make the fuel pump louder before it dies?? That was my only idea. Fuel gauge is still wonky on it, so I'll be replacing it regardless. I was just curious if anyone else had ever heard of this?

jsoden · June 5, 2011

Also replaced my fuel filter and it finally started doing the loud hum again. I think a combo of lots of things caused it to overwork. Hopefully replacing the whole unit will fix all the problems!

londo · June 5, 2011

Also replaced my fuel filter and it finally started doing the loud hum again. I think a combo of lots of things caused it to overwork. Hopefully replacing the whole unit will fix all the problems!

Can't help with that, but a little advise after changing the pump, "do not run your truck/tahoe etc below a 1/4 tank if possible. You will see after removing the old pump that it sits inside a small resevoir. This gets filled up when you fill the tank and is the only thing that cools the pump as fuel level drops. After 1/4 tank you are relying on a couple tablespoons of fuel to cool the pump. Yep thats right cool with fuel ! Kinda F'd up design if you ask me. The pump is easy after you get the tank out. About 2 hrs. in a driveway up on 4 {really good stands}

rgv · June 5, 2011

Can't help with that, but a little advise after changing the pump, "do not run your truck/tahoe etc below a 1/4 tank if possible. You will see after removing the old pump that it sits inside a small resevoir. This gets filled up when you fill the tank and is the only thing that cools the pump as fuel level drops. After 1/4 tank you are relying on a couple tablespoons of fuel to cool the pump. Yep thats right cool with fuel ! Kinda F'd up design if you ask me. The pump is easy after you get the tank out. About 2 hrs. in a driveway up on 4 {really good stands}

Myth.

The return line going back to the tank dumps directly back into the reservoir or bucket.

If your engine is running, your fuel pump is submerged in fuel.

AirForceAngler · June 5, 2011

Myth.

The return line going back to the tank dumps directly back into the reservoir or bucket.

If your engine is running, your fuel pump is submerged in fuel.

Your advice is the myth. I'm pretty sure even the owner's manual will warn against running below 1/4 tank. We've been through this all before also.

rgv · June 6, 2011

Myth.

The return line going back to the tank dumps directly back into the reservoir or bucket.

If your engine is running, your fuel pump is submerged in fuel.

Your advice is the myth. I'm pretty sure even the owner's manual will warn against running below 1/4 tank. We've been through this all before also.

Ever dissasemble a fuel pump module to see?

I have.

The return line feeds into one of the hollow steel guide rods and into the bucket.

Kindly show us where in the owners manual that warns against running below 1/4 tank because it may cause fuel pump damage.

Please.

jsoden · June 6, 2011

Yeah, it's going to be a pretty simple job. One trick I learned is that I don't have to drop the tank. Just take out the front four bolts holding the bed on and loosen the back two. Then I can just jack the front of the bed up and have plenty of clearance to just reach in and take it out. No dropping the tank and a lot easier. I never let my tanks go below 1/4. In the winter, 1/2. I don't want condensation forming in the tank and rusting everything. Not sure exactly how they're cooled. I'll let you two decide that one!

rgv · June 6, 2011

Not sure exactly how they're cooled. I'll let you two decide that one!

If you have the new one ready to go, find out for yourself.

Blow into the return inlet in the top (marked R) and see where the air blows.

I'm not sure what a GMT800/900 fuel pump is rated at, but an LT1/LS1 pump is around 200 Lph, or around 50 gallons per hour. Under the worst conditions you might burn 10 gallons per hour. That means that 40+ gallons per hour get returned past the fuel pressure regulator back into that little bucket and overflows out the top into the tank.

The plastic bucket stays full of fuel when the engine is running.

1/4 tank, 1/8 tank, or full tank, the metal pump stays submerged in fuel.

jsoden · June 9, 2011

I did notice that when I have over 1/2 a tank, it's a little quieter, so I imagine it's probably completely covered, but once it gets down to around 1/4, it's noticeably louder. I'll check it all out and tell you what I see!

az'03Silverado · June 9, 2011

Not sure exactly how they're cooled. I'll let you two decide that one!

If you have the new one ready to go, find out for yourself.

Blow into the return inlet in the top (marked R) and see where the air blows.

I'm not sure what a GMT800/900 fuel pump is rated at, but an LT1/LS1 pump is around 200 Lph, or around 50 gallons per hour. Under the worst conditions you might burn 10 gallons per hour. That means that 40+ gallons per hour get returned past the fuel pressure regulator back into that little bucket and overflows out the top into the tank.

The plastic bucket stays full of fuel when the engine is running.

1/4 tank, 1/8 tank, or full tank, the metal pump stays submerged in fuel.

+1 plus there's always fuel going through the pump, thus, cooling it. I don't care anymore. I had the dealer put in a new pump with a lifetime warranty. If it fails, it gets fixed free.

rogerf · June 11, 2011

I did notice that when I have over 1/2 a tank, it's a little quieter, so I imagine it's probably completely covered, but once it gets down to around 1/4, it's noticeably louder. I'll check it all out and tell you what I see!

I had a late model Impala where the pump would howl badly. Took awhile but eventually discovered it was related to the fuel blend...the more alcohol, the worse it got. I used a very small amount of soybean oil-based diesel fuel conditioner designed to lube injectors which got rid of the problem.

jsoden · June 12, 2011

Well, replaced it. Fuel gauge works great and it's very quiet now. After two of the central bolts on my truck bed stripped while trying to LOOSEN them, I came to the painful realization that I was going to have to drop the tank. Dropped it, and came to the more painful realization that they sent me the wrong damn pump. Fortunately, I was able to swap out the plugs on the pumps, and there was a spot on the new one for the evap sensor, so the old one just dropped on. Got it all put back in and began the painful task of putting the tank back in place. Used the jack to raise it up, but the damn thing wouldn't line up right. Finally got it into place, and had to strain to get the bolts back in. As it turns out,,, this was probably a two person job. I'm just glad I had the foresight to run my tank to less than 1/8 before starting this task just in case it didn't go smoothly. Hello Murphy,,, I am familiar with your laws. Just glad I got it done and all works well now.