Fuel Tank

[WCoberly]

The other day when I stopped down and looked at my truck (in the shop for collision repair), the box was off and I looked at the fuel tank. The tank appears to be divided into three sections. The center section is where the fuel pickup unit is. The front and rear sections have a hose barb attachment for some unknown reason to me. The rear hose bard had a rubber hose plug slid over it, but the front one did not. I was wondering what these two hose barb connect points are for, and if there should be a plug on the both of them? The reason I ask is that there was dirt on the top of the tank near the hose barbs, and if I was to power wash underneath the truck, I could potentially get water shot into the barb and the water could end up in the tank. Thanks for any information.

 

[Badunit]

There was a recent thread about this problem. Maybe it was on another site. I can't seem to find it right now. Anyway, it said the two nipples are check valves and are for emissions equipment on gas powered trucks. The thread was about how someone thinks water is getting into their tank through one of the nipples. Pg 14-2 of the factory service manual has a drawing of the tank and the rest. I can't see any use for them on a diesel and, if mine are not blocked off with a cap, I will be making caps for them just to be on the safe side.

 

[Badunit]

https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=88531&highlight=142

 

[Rosco]

I had followed the thread that Badunit referred to when it was active and I was a little concerned. However, One thing's for sure. The only way water will get into the tank is if these barbs truly have check valves that flow "into" the tank.



My reasoning is due to the fact that I, along with others have filled their fuel tanks to the very top (fuel in filler neck) and have never had fuel "exit" through the barbs.



Maybe someone could try attaching a length of hose to the barb and see if low pressure air will enter the tank. If it does there is a check valve and if it doesn't then the barbs must be plugged from the factory.

 

[rbattelle]

Those nipples are there for the 1/2 ton trucks, which use the same tanks. They are connections for the EVAP canister, and must be plugged on the Diesels.

 

[Badunit]

You can blow air in and suck air out with no resistance. Maybe the "check valve" part has something to do with if the tank is upside down (i. e. , in an accident). Sloshing fuel would probably close it off too, if that's the case.



I capped both of mine today.

 

[rbattelle]

Originally posted by Badunit

You can blow air in and suck air out with no resistance.

You really shouldn't suck or blow your fuel tank. :-laf

 

[Badunit]

Alrighty then, I'll rephrase it for those with dirty minds: If you apply air pressure to the hose barb, air will flow into the tank. If you apply a vacuum to the barb, air will flow out of the tank. There appears to be no restriction in either direction.

 

[Badunit]

After taking a long drive today, I removed one of the hose caps I installed and the tank sucked in air for a good 30 seconds. I was parked on a slight hill so I assume some fuel was locked into that end of the tank (like a gas can before you open the vent). The reason I removed it was because, every now and then, I get the smell of raw diesel and I was wondering if the tank was burping fumes or something due to these nipples being capped off. I didn't prove anything one way or another but I'm starting to wonder if these vents actually do something useful and capping them isn't the best idea.

 

[Prairie Dog]

Originally posted by rbattelle

You really shouldn't suck or blow your fuel tank. :-laf

Sounds like he really loves his truck

 

[Badunit]

Actually, I do love my truck but not in THAT way.

 

[Joseph Donnelly]

If I recall, the gist of the thread posted by DCTECH was that we should put a hose on the open hose nipple near the front top of the tank. I did so (1/4" hose), and tucked in between the side of the tank and the steel shield that runs along the tank.

 

[scotty1]

Can we use one of those nipples as a fuel line from a transfer tank in the bed?

 

[Badunit]

Good question. They are 1/4" nipples. However, they are "check valves". I assume they keep fuel from coming out but I don't know what they do if you are forcing fuel into them.