Engine/Transmission (1998.5 - 2002) fixed it

[CATCRACKER]

mystery sucking sound when i take off the gas cap fixed. there was no red nipple on the overflow valve on my tank but upon taking it off and taking it apart i learned it got mud stuck in it . i cleaned it and bam no more sucking sound a 1psi higher fuel press i have the original lift pump on this truck with 115K go figure. thought this might help some of you guys.

 

[lschultz]

Did you mean mystery sucking sound when you took the DIESEL cap off?

 

[AggieJustin]

Better make that the DIESEL cap. Don't want to get caught running the red stuff

 

[rashwor]

Mine does this too...

Mine does the same thing Cat. How easy is it to get to? What tools do I need to remove it? Do you need to drop the tank? Details if you please... .

 

[CATCRACKER]

what, you guys dont have the new and improved cummins that runs on gas:-laf ... anyway to answer rashwor i actually fixed this problem about 3 months age but figured i would help someone who might have this same problem and i guess i worked.



(fisrt make sure there was not a red nipple (left on from the factory) on the end of the overflow vavle on top of the tank if there is a red nipple remove and leave of. if no red nipple drive truck for a while to make sure pressure has built up in the tank and then stick a thin piece of wire in the end of the overflow valve nipple if it releases pressure this is your problem either it is malfunctioning or it has dirt in it). i stuck a piece of welding wire down the end and i heard a release of pressurized air. i knew the valve was malfunctioning.

fix: at your own risk!

1. dont have to drop the tank. access tank from the passegers side

2. tools, screwdrivers (flathead) adjustable pliers, light,shop rags

3. the overflow vavle is on top of the diesel!!! tank. it will pop off with some prying around the edge with screwdriver (don't damage the gasket)

4. once removed take it apart(simple) and clean it. i cleaned it with whatever i had. i used carb cleaner.

5. reassemble and pop back onto the tank (this is the hard part)

tip: place valve on top of tank and use the opening force some pliers braced against the frame to pop the vavle back onto the tank.



hope this helps. if it has always done this (sucking) since new it will probably be the red nipple problem unless the problem just started i dont know your level of mechanical skill but have fun and never be scared to try anything. persistance is the key

 

[rashwor]

Thanks Cat.

Thanks Cat. Mine has done it since i bought the truck new. I will check it out. I asked the dealer about this a long time ago and they said it was normal I did not think it was, but... One question, can you see the valve from the passenger side of the tank, or are there fuel lines and such in the way where you can't see it?



Thanks again.

 

[CATCRACKER]

it is hard to see b/c it is on top of the tank. get a good light. it is the cap without the hoses on it. you will see it it has a little tit sticking out your probably has the red cap on the end of the little tit.