New fuel issue

[Whiplash2130]

1993 2.5L
A new humming noise was really bothersome on my 190 mile ride today. On the way back I stopped for fuel. After refueling the noise was completely gone. By the time we got home, 25 miles, the noise was back. I left the engine running, removed the fuel cap. There was some pressure, but did not resolve the sound.

 

[Flyer58]

Where was the noise from? Front - engine or back- fuel pump?

Did the sound change with engine rpm or remain a constant hum?

Did you make any changes to the fuel tank vent to get the 20 gallon capacity?

 

[Whiplash2130]

Where was the noise from? Front - engine or back- fuel pump?

Did the sound change with engine rpm or remain a constant hum?

Did you make any changes to the fuel tank vent to get the 20 gallon capacity?

Sounded like rear axel area, but hard to tell for sure. I think if it were the fuel pump, the sound wouldn’t go away when fueling to full.
No, constant drone - like a fan turned on.
Fuel tank changes are to be made next week.

Should there be pressure in the tank while running? Bad venting fuel cap?

Thanks

 

[Flyer58]

Sounded like rear axel area, but hard to tell for sure. I think if it were the fuel pump, the sound wouldn’t go away when fueling to full.
No, constant drone - like a fan turned on.
Fuel tank changes are to be made next week.

Should there be pressure in the tank while running? Bad venting fuel cap?

Thanks

I don't know about the pressure, I've never checked that but when I fill my tank at the gas station I do notice a small puff of air when removing the gas cap. I just assumed the cap has a one way check valve to let air in but not out. As gas heats up during the day or while driving it will expand and can build pressure.

I'll be pulling my fuel pump soon because the fuel level sending unit attached to the pump is bad. The pump is submerged in fuel so to me it makes sense that it's quieter with a full tank than when close to empty. Maybe running it out of gas picked up some crud to make it louder.

Turn the key on and off a few times without starting the engine and listen for the pump to run for a few seconds. See if that's the sound you hear. Maybe get a helper where you can get back by the tank to help pinpoint the sound.

I changed out the pump in my Chevy truck several years ago which had a similar submerged set up. The new pump really squealed loudly on cold mornings but still had good pressure. (Don't go with the cheap pump). Since I had to remove the bed of the truck to get to the pump I learned to live with it.