1978 Suburban fuel fill issue
 

Guys, appreciate your ideas on this one. A buddy just completed an LS swap on this 78 Burb. Filling the fuel tank is very slow and difficult. Condition existed before the swap. Still exists with the vent disconnected at the tank. Gas just backs up in the fill pipe.

I've searched for ideas here and I did find several threads about the issue on trucks with no good solutions.

We figure it is the small diameter of the fill pipe coupled with the very slight down angle that causes the fuel to back up. Tanks inc has a larger diameter tank neck that we will try.

Unless there is something I am missing? Appreciate your ideas.

Re: 1978 Suburban fuel fill issue
 

Fill pipe...

Re: 1978 Suburban fuel fill issue
 

Fill

Re: 1978 Suburban fuel fill issue
 

I think your on the right track...your displacing air with fuel...I would think the fill vent is the issue...as long as the vent is behind the pump nozzle it should work...I assume yall made sure the vent tube isn't clogged or kinked...but I guess you eliminated that by removing the vent at the tank...maybe its the tube inside the tank...

Re: 1978 Suburban fuel fill issue
 

Thanks Mongo. Yes, fill issue still exists with the vent tube open at the tank.

Re: 1978 Suburban fuel fill issue
 

I wonder if the fill tube has a restriction...may need to pull the tank and have a looksee...what's that hose clamp in the middle of the fill tube in the last pic?....something looks odd about the hose right there...looks like a hose stuffed inside a hose...

Re: 1978 Suburban fuel fill issue
 

Will check and verify. Appreciate the input!

Re: 1978 Suburban fuel fill issue
 

Under hood shot just because we all like pic's. Swap was completed using the Holley mounts.

Re: 1978 Suburban fuel fill issue
 

May be an anti-siphon device in the metal part of the filler tube?. Loosen a couple of hose clamps and undo a couple of screws and remove the filler neck completely then have a look see. The 'burbs did not change a whole lot in the 18 years they were built. I'm on my 3rd square body without a problem filling the tank

Re: 1978 Suburban fuel fill issue
 

Thanks KW, will do.

Re: 1978 Suburban fuel fill issue
 

There were no restrictions in the hose. The small diameter seems to fill and back up, similar to a funnel with a small neck.

Looking at making use of Tanks 2" elbow at the tank for a larger diameter fill hose.

Re: 1978 Suburban fuel fill issue
 

sounds like a good plan..

Re: 1978 Suburban fuel fill issue
 

Hope so, like Kwmech mentioned above he has had three of this body style with no problem on the fuel fill. This one just isn't happy.

And it could always be something simple we overlooked...keeps us all humble when we do that. Ha...

Re: 1978 Suburban fuel fill issue
 

I'm still wondering about the vent because they fill fine with stock hardware when in good order. You removed the vent lines, did you blow out the hard line on the tank where the vent lines connect? Run a pipe cleaner through it if you can.

Re: 1978 Suburban fuel fill issue
 

Good idea John. The vent through the sending unit is clear and tank still didn't want to fill with the vent hose disconnected at the new sender. Here is is removed from the tank.

Re: 1978 Suburban fuel fill issue
 

How are you filling the tank? At a gas station pump or with a container? More then one station if at a station? Maybe the pumps at the station are too fast. I have had that problem before. My 84 crew cab diesel has to be only on the first stop with the new diesel pumps. Our gasser Sub. most pumps are fine but every once and a while one will be too fast.

Re: 1978 Suburban fuel fill issue
 

Cheepin, good thought. A hand held gas can would overfill the fill pipe causing a back up. Happened with any pump too.

My buddy replaced the smaller neck and fill with the 2" diameter one. That eliminated the problem with filling the tank.

Appreciate all the input guys.

Re: 1978 Suburban fuel fill issue
 

Interesting. The stock neck looked normal when removed?

Re: 1978 Suburban fuel fill issue
 

Yes, there were no restrictions noted on the fill side.

Re: 1978 Suburban fuel fill issue
 

You're right!
It is something simple.
Every truck I've owned has been a pain to fill.
My solution is to rotate the fuel nozzle handle about 180 degrees if possible. THe handle will be upside down. The fuel will flow at full warp with never a stop.
Try it!

Re: 1978 Suburban fuel fill issue
 

I don' know about you guys, but on my Blazer if I hold the fuel handle all the way tilted up so the nozzle is pointing as far down as possible, mine will fill correctly. My opinion is it's just the fill port is at the wrong angle. You'll notice all newer vehicles have the fill tube in the car at like an 75* angle which matches the pump fill nozzle.