The fuel pump on my 1994 4WD S-1- Blazer will whine/or howl after shutting down after a short startup of a few minutes. On longer drives, no noise. Is this a symtom of fuel pump problems?

 

Some fuel pumps whine as they get closer to the minimum pressure for the truck to run. Blazers have famously bad pumps. You should be able to hear it for a couple seconds when turning the key to run. But not on the road.

Mine did the same thing. 2 weeks later it completely died on me.

 

ive had my 93 for 4 years now and that pump has been louder then heck the day i bought it and it still works to this day. alot of chevy pumps seem to be loud like this for some reason. it can mean its bad but doesnt always. i kinda like it. if i dont hear it and my truck wont start i know what the problem is

 

I had a 91 blazer years ago.The pump was good and normally quiet but the top of the tank(along the seam) leak going up hill.Being in WV I had to change the tank.I bought a cheaper tank without the plastic baffling inside and man it got noisy in the cab.

 

[ fuel pump on my 1994 4WD S-1- Blazer will whine/or howl after shutting down after a short startup of a few minutes. On longer drives, no noise. Is this a symtom of fuel pump problems?[/quote]


Here's what I was told.

The fuel pump is powered by the ign switch and also by the oil pressure switch. The ign switch supplies initial elec power, then the oil pressure switch takes over. The power from the oil pressure switch cuts off when the oil pressure drops below 4lbs. When you turn off the switch, and your oil is cold & thick, your fuel pump may run for several more seconds until the oil pressure drops. And the relay also enters into all this. And the ECM.
So, your fuel pump running after shutdown isn't "un-normal".
Noisy = no comment. And like 'workshop' (below) said, maybe your fuel is getting kinda lumpy.

If you disconnect the oil pressure wire, the truck should start but immediately stop when you release the key. (It isn't sensing oil pressure) A good way to check oil sender power.

And, some models are also controlled by the ECM.

This is what I understood pertaining to my truck. Other models could be different.

 

My pump started to have the symptoms you describe. It would be noisy at times, quiet at other times. After a couple months it started to happen more often, then eventually went to always make the noise. I decided to be safe, and replace it with a Delphi replacement since its only about $70 and a few hours of my time.

I found that the old pump was clogged with dirt and crap, couldn't even see the fins inside the motor. Put my new pump and strainer in, and all my noise is gone.

I think it's time you bought a new pump. It's possible you could get a few more years our of this one, but its also possible today will be the day it decides to quit. Why risk it?