My '96 Chevy C3500 6.5L is acting like it's almost out of fuel and when I "wiggle" it back and forth it smooths out for awhile. Both tanks are full, filter is new. It's now occasionally not starting. Ever since I had the heads replaced (3 mos ago) my fuel gauge hasn't been working properly. Don't know if it could possibly be related or not. Please help. Gus

 

Wiggle what? Getting good flow out the t - valve? If not test the lift pump. Check that your fuel cap is venting. Possible dirty sock filter in the tank.

 

X2 on fuel sending unit sock

 

This!

 

When I wiggle the truck back and forth while still driving down the road.

 

Thank you, I'll try to drop the tank and check that filter.
Gus

 

Don't forget to check lift pump and fuel tank cap for proper venting first. If the sending unit has been replaced before, it's very likely it has the wrong tank sock (strainer) on it. Diesel and gas used different strainers but it seems all the aftermarket senders come with the smaller gas sock installed. Otherwise, if you got a batch of really bad fuel or something, even the correct diesel sock will plug up. The diesel sock has a bypass in it that will still allow some fuel flow if it gets plugged or the fuel gells or whatnot.