HELP!! 1997 chevy making weird NOISE!!

[mbecke2]

1997 chevy cheyene 5.7L 350 Truck has 140,000 miles. I noticed my truck hasnt really been running right lately. When shifting in low gears it makes a wierd noise. Now it is worse and sounds like a low hummin sound. So I put it in park and got out and noticed I couldnt hear the low hummin sound from the motor, but when I got under the cab near the rear tires I could hear the hummin sound a lot better. Im not sure what the problem is, but sounds like tranny to me. Any suggestions??

[brcidd]

Try this-- With engine oiff-- listen if it hums just by turning ignition key on.... see if hum lasts for 2 seconds...then quits.....

There are a lot of fuel pumps that hum good and loud- and does not necessarily mean anything is wrong.

A fuel pressure check will confirm if this is the cause of "not running right"

[mbecke2]

Yea I noticed it IS the fuel pump. But why is it running constantly. I've never seen it do this before. I installed this fuel pump about a year ago myself and havent had any problems with it. Could it be shorting out?? Should I check the wires?

[JMFite]

with the key on but the engine not running, the pump will run and then shut off. with the engine running, the pump will run all the time. I have had some trucks that you could hear the pump running over the engine.