Engine/Transmission (1998.5 - 2002) Lift pump testing & fuel tank cap vent

[Gordon Maney]

A first question: Is the cap for the fuel tank vented to allow air to enter the tank? It seems that mine (2001) will make a bunch of air rushing sound when I remove the cap at a fueling. I don't recall that it has always done that, but admit to not being sure. Is this a normal situation? Is the cap supposed to be vented?



A second question: Do you find that if you go to a dealer where you did not buy the truck, they are not helpful in matters such as testing, diagnosis, replacement, of lift pumps? Over a period of time I figured out that the dealer where I purchased my truck is not as technically capable as I might have hoped, and would rather go to a different dealer on this, but am uncertain as to the reception I would receive. Thoughts on this?



Thank you... .

 

[nps]

Did you read my reply to your 911 thread?



If $ are involved, any dealer will be helpful.

 

[Thomas]

A first question: Is the cap for the fuel tank vented...

The model year 2000 (and likely model year 2001) Factory Service Manual mentions the following about fuel tank filler tube caps:

OPERATION The loss of any fuel or vapor out of the fuel filler tube is prevented by the use of a pressure-vacuum fuel fill cap. Relief valves inside the cap will release fuel tank pressure at predetermined pressures. Fuel tank vacuum will also be released at predetermined pressures...


The tank on diesel-fueled trucks is vented to the atmosphere via the vent at the rollover valve on the fuel tank. The only need for the relief valves inside the cap (mentioned above) would be in case the check valve/vent at the tank (rollover valve) became blocked. This blockage could be caused by a red cap left on the vent at assembly. This source of blockage has been documented in TSB's. I've never read of a red cap left on the vent stopping the mighty Cummins or totally collapsing a fuel tank-probably because of the vacuum relief valve in the filler cap.
The gasoline-fueled trucks have a similar setup, with the following differences. Trucks with 35 gallon tanks have two rollover valve/vent assemblies. The vents are not open to the atmosphere. They are plumbed to a source of engine intake vacuum via charcoal cannisters.
The gassers need an emmision system on their fuel tanks. The diesel trucks don't.

Inspect the fuel tank rollover valve for restrictions or that the shipping cap has not been left on the end of the valve.

 

[Gordon Maney]

Did you read my reply to your 911 thread?



If $ are involved, any dealer will be helpful.

Yes, just now. Sometimes the notification e-mails do not get to me right away. Thank you for your reply. I am going to buy a new cap.



The reason I asked the dealer question is that years ago I was a mechanic in two dealerships. Neither of them wanted to do warranty work on vehicles they did not sell.



When you talk about dollars involved, are you including warranty dollars, or customer-paid service dollars?

 

[nps]

When you talk about dollars involved, are you including warranty dollars, or customer-paid service dollars?

Customer $ are always more in demand, but I've not had problems getting a reputable dealer to do warranty work. Now me wanting to have them do the work is another story.