When i fill up and take my cap off of the tank it hisses like the fuel tank isn't breathing. Is this a problem could it affect mileage and does anyone else truck do this. Just thing about the little simple things since diesel isn't getting cheeper

 

Sounds like the vent is clogged.

 

Where is the vent at exactly!

 

I think it's that lone teat at the top of that with the red circle (with the fuel in/out teats).



Seems like there'd be a screen or filter there

 

You can see mine to the left of the cross member I think there is a bit of paper towel suck in there....

Kidding aside, on BC847's picture he pointed out the pressure relief/rollover valve. No screen that I have ever seen.

 

Rich, on my mess, that line with the NASA filter on it ( ) runs up to the tank fill bung for venting the tank during filling (I think?). The actual fuel fill pipe goes right below it.



The FSM talks only about the roll-over/pressure relief valve and doesn't say positive or negative.


Where is the fuel tank vent on a '92 ~ '93?

 

Reviving this one.

My tank is building lots of pressure/vacuum. Enough that it's getting very hard to loosen the cap. With access to the vent in the pump module difficult at bes, what would be the problem installing a vent in the large line for venting durring fillups? Other than spillage durring a roll-over.

 

Mine wasn't that bad, but it's definitely that vent or pressure relief, whatever you want to call it. I unplugged it by sticking a little piece of wire in there and scraping it around. Then I connected a piece of rubber tubing with some cotton stuffed in the other end and tied it up on the bottom of the bed. Then I got a new locking gas cap and "vented" that with a drill.

 

I have had two of these trucks that developed an unwanted rust vent in the fill pipe under the portion that gets covered by the connecting hose. Dirt and water thrown from the tires accumulates between the hose and pipe. I remove them and use solder to fill the holes.

 

It could be crank case pressure entering the return line in the fuel system. Have you recently installed injectors or had pump work done?

 

No pump work or injectors. Problem has gotton prgressively worse over time. Not sure I folloe the crankcase to return line problem.

 

Not on this motor it can't.