Engine/Transmission (1994 - 1998) cab noise from fuel lines

[SMorneau]

Since I had my 6 speed conversion done I have periodically noticed a thumping noise that is in time with the engine and sounds like a loose tailpipe hanger. Well tonight I started by putting my ear on the sheet metal all around the truck and it was most prevalent on the lower rear cab drivers side. I got out the stethescope and tracked the noise to the frame on the drivers side. Further exploration showed it was the loudest on the straight section even with the drivers door (standard cab truck) and looking a little deeper took me to the fuel lines that are anchored to the inside of that frame rail. There is no doubt the thumping is being transmitted thru the frame into the cab mounts by the fuel lines.



The reason I mention the 6th speed conversion is the cross member was changed and that may be related and it was the first time I ever noticed the noise. I don't think the fuel lines were ever disturbed during the operation.



My fuel heater is toast but I cannot say the temp make this noise louder only that I don't always notice it.



With the stethescope on these lines it is really a loud hammering. Is this normal? I put the stethescope on the overflow valve and the lift pump and did not get a thumping or anything I would say sounds abnormal. I will try and get it down to one of the lines but any wisdom here would be appreciated. At 260kmiles I am not against putting a new lift pump in the truck if it is a problem.

 

[HEMI®Dart]

I get the same noise in my truck. Sometimes it's a Swish Swish type noise. If I get down near the return line it thumps. I notice it more in the cooler weather. I don't think a new lift pump would do any good.