I am the original owner of a 76 F350 supercab, 460/C6, with OEM dual tanks. The rear tank has always "puked" fuel out the filler/cap on to the side of the bed. This happens from about half tank to full, and is caused by sloshing in the tank as the rear wheels track over uneven surface, like entering a driveway cut. I have tried everything I know to do, short of emptying the tank and not using it. Every Ford truck I've seen with a rear tank and exposed gas cap has a fuel stain right below the cap. I've "doubled" the gasket on the cap, put a small drain hole in the filler neck just behind the cap, but nothing has solved the problem. It's a poor design, with the tank mounted perpendicular to the frame and the top of the tank being only slightly below the inlet to the filler neck. I guess if more thought had gone in to baffling the neck correctly, the "puking" would not occur. If anyone has a fix for this issue, I'd certainly like to hear from you.

Thanks

 

76 had a problem with that =\
Try re-positioning the filler neck

 

Do you mean cut another hole in the bed side? I won't be doing that.

 

Hopefully that will work for you. I have a 76 F-250 with the OEM dual sidetanks and while both are are pain in the rear to fill. Only on one really hot day with the tanks filled did they have a spillage problem. Otherwise the only spillage is just upon filling which must be done slowly and at the right angle.

 

You're talking about sloshing and not the problem with filling. Right? I see you tried doubling the gasket but have you tried a new/different cap? One that fits tight?

While I don't have a exposed fill; Even with fill tanks and a somewhat loose locking cap it doesn't slosh.

Might be worth finding tight standard cap that fits the filler neck. Maybe some one in the past got one that somewhat fits; but is wrong. I've heard lots about the filling problem but not the "slosh".

.

 

My truck has the XLT trim package with the wide white factory decal from front to rear. The driver side decal for the bed was replaced under factory warranty back in 1978 because of the "sloshing" that stained the decal below the gas cap. My gas caps are the OEM large locking caps. I could try another one, but doubt it would fix the problem. I think LMC or DC have them. The last time I repaired the decal, the body shope painted over the decals with flex bumper-type paint. This paint has crinkled under the cap, so will probably take it in and have the side decal repainted, and then just keep about a 1/4 tank of gas.

 

I do not think so. On my truck to me the the filler neck would a rubber hose that runs from behind the fill cap area to the tank. Maybe a longer piece or different angles will help. I have never had the same problem as you in 31 years and over 400,000 miles of driving my truck. Good Luck

 

Try this cap from D.C.-Part # D4TZ-9030-A
$8.00 worked for me on my 74.Gas no longer sloshes out from around the cap while driving.My problem is filling it.Have to pump real slow and have the gas nozzle turned a certain way.I'm going to fix that real soon.I'm going to move the fill hole into the bed or relocate it behind the the drivers side taillight.

 

Thanks, BigFoot; I'm going to order that cap from D.C. I think one issue with my locking cap is that I believe some of the sloshed fuel may be escaping through the key slot--it's definitely not "water-tight". I certainly hope the D.C. cap will work for me.