I've been fixing up a new to me 1996 F Superduty with a 7.5L big block to be my toy hauler. I started with brake lines, rear pads and a caliper (need to do the other now!)

Anyways, this thing is slow as hell to fill with gas. I only use the front tank, and when I gull I have to pump less than a tenth of a gallon and wait for it to make its way to the tank. I have heard of such things as a clogged fuel vent, do these trucks have the vent on top of the tank, or just the cap vent? Also, this is a flatbed, so could it just be the lack of slope from the filler neck to the tank?

This could be unrelated, but when I run the truck for more than 15 or 20 minutes it starts to studder as if it is running out if fuel or air, is it possible that the tank is pulling into a vacuum and the pump can't deliver enough fuel? I will report back with fuel pressure readings when I get the chance.

TIA

 

I was under the impression on these trucks the slow filling was due to a crack on the internal pipe of the fuel filler neck. But yes there is a vent at the top of the tank.

 

Also, if you have the wrong gas cap, it can cause a vacuum condition like you described. There are different types of venting for tanks but usually, there is a vent tube at the gauge sending unit on top of the tank. A hose goes from the vent tube to the filler near the gas cap. The vent hose can get pinched or clogged and cause the slow filling that you are describing.

 

What's the slope of the filler like? It can be tricky to get it right especially if the flatbed sits close to the frame rails. To test, bring a 4x4 piece of lumber with you to the gas station, drive the driver side rear tire up onto it at the pump, and see if the fill rate is better. I've developed an eye for pumps that have the ground sloped away, and also have figured out which pumps in town are overly sensitive to kicking off.

 

LOL forgot about the 4x4 trick. Haven't seen that done in years.

 

I was considering bringing a log or 4x4 to the gas station next fillup, good plan, I'll give it a go. As far as the filler neck goes it wouldn't surprise me of she's messed up. The one for the rear tank is rotted off of where the bung is welded to the bed rail.

For the rear tank filler neck, do you recommend buying OEM part or should I fabricate my own? They were around 140 bucks at the local parts store. Maybe I'll take a trip to the junkyard.

The path for the filler tube goes between the flat bed and the frame rails, and it's a narrow path. The tube is partly pinched, bu I wouldn't call it blocked.