Fuel Sytem Problems..still

[stanwood]

I'm at my wits end! I replaced my gas tank due to a mishap on a hill that was steeper than it looked. Since then nothing has worked right.

The truck will run for a minute and then act like it runs out of gas. I have replaced the fuel pump, auxillary pump, filter, fuel lines - coming and going. Does the thing run on some sort of vaccuum that I do not know about? I can take the line from the aux. pump, run it directly into a can of gas and it'll run all day. I thought maybe the lines were pinched at the tank but I rerouted them along the underside of a brace under the bed. Does anyone have any ideas?

Thanks, Stan

[Wesdog]

Does this happen when tank is full, partially filled or close to empty? Do you have a fuel return line to the tank? Are you using an OEM style inline filter with the return line nipple and if so is it connected correctly and is the return nipple at the top of the filter with the filter installed horizontally? Do you have a vent line? Is there a check valve in the ventline and is it working correctly? Have you inspected the carb fuel inlet and needle/seats to confirm there is nothing restricting the flow of fuel into the float bowl? Can you install a fuel pressure gauge near the carb inlet to check fuel pressure when the problem is present?

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[stanwood]

Answers to your questions:

It started when it was full. I have siphoned out all but a gallon or two. I am using the OEM style filter and it is installed correctly (full line on the "bottom". There is a vent line but it has no check valve - it goes straight up to near the top of the neck of the filler tube. I don't have a fuel pressure gauge but if you pull the fuel line before the filter it sprays out (when running from a gas can).

The problem seems to exisit from the sending unit to the aux. pump. I thought it might be a vaccuum forming so I took the fuel cap off - it worked. Drilled a hole in the fuel cap - it didn't work. Any other ideas?

thanks

[Cecil14]

If it works with the fuel cap off possibly the vent in the cap isn't working right. Have you tried a different cap?

Anthony

[Wesdog]

My 76 tank has the 1.25" filler inlet, 5/8" vent tied into the filler neck and a 1/4" vent tube at both the front and rear of the tank. The two 1/4" tank vents are connected via hoses to a liquid check valve and the check valve outlet goes to the charchol canister. I have a non-vented gas cap. The two 1/4" vents allow air into the tank whether when the vehicle is level or inclined up/down. Did your old tank have these extra vents?

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[ July 26, 2003, 02:17 PM: Message edited by: Wesdog ]

[stanwood]

Wesdog,

You've got more vents than I. There are no vents on the new tank, only the 1/2 in or sohole that conects to the hose that connects to the vent hole in the top of the filler tube. The gas cap is not vented and the local NAPA store didn't have one. I'll need to find one but for now I will be stuffing a grease rag in there.

I tested it again without the cap and it ran fine. I put the cap back on (the one I drilled a hole in) and it died in about 10 seconds. That seems too fast. I'll try it again without the cap and see how long it'll run.

I do know that the Chief and J Truck have different tanks and set ups.

-stan

[joe]

Originally posted by stanwood:
Wesdog,
There are no vents on the new tank, only the 1/2 in or sohole that conects to the hose that connects to the vent hole in the top of the filler tube. On a stock 76 truck tank there are two other vent hoses besides the one for the fill pipe. They go to the check valve and from there routed into the charcoal canister.

[Wesdog]

You could probably add a tee into the 1/2" vent hose near the filler and add a new ventline with check valve to a canister. I may have to do a similar mod to my 77 Cherokee cause it's fuel tank is like yours and was designed to be used with a vented gas cap.

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[stanwood]

I took the cap off again and rode around for about 10 minutes and had no problem. I'm going to have to find a vented cap.

As for stock 76, I don't know, but mine has no charcoal canister, but the sending unit has another line coming out of it but the PO had drilled a screw in the opening to shut it off. When I bought a new tank I did not get a new sending unit. It worked well before so I did not think to change it.

-Stan

[joe]

A 76 stock system did come with a charcoal canister and a check valve. The other nipple on your sending unit is for the fuel return line that runs from the fuel filter in the engine bay.

[stanwood]

I'm not doubting you, Joe, I'm just saying that mine doesn't have a canister. As for the the other nipple, I do have that hooked to the return line. There's a third nipple, this one comes out of the sending unit next to the fuel line.

[joe]

Hmmm...3 nipples on the sending unit huh? Ya got me there Stan, I've never seen a 3 nipple sending unit? I have no idea what a 3rd line would be for?
A stock set up just has the out to the pump line and the return line from the filter on the sending unit itself and the vent lines come directly from the tank body one from each end of the tank on top.

[Wesdog]

Maybe that isn't a stock sending unit or it's been modified. I have a Cherokee and the fuel level sender is totally separate from the fuel pickup/return assembly and is installed in a separate opening in the coffin style tank. Never seen a J10 tank so I have no idea how it's setup. Sounds like you might be able to use the 3rd nipple as a vent if it does'nt internally extend past the plate into the fuel. Messing with the fuel system requires care so be certain what you are doing is safe.

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[stanwood]

Here's a pic of the gas tank

http://www.bjsoffroad.com/fsj/fuel/14-6013t.jpg

I couldn't find one of the sending unit.

Wesdog - I was thinking the same thing you were. - use the third nipple as a vent. Maybe run it up to under the rail in the bed next to the cab. That way it wouldn't get water in it. But to do that I wiould have to pull the tank for the 6th or 7th time. Instead, I took the paper gasket out of the filler cap, drilled 4 holes in the underside of the cap, and one to the outside. We'll see.

[Wesdog]

You should be able to get the canister, mounting bracket, checkvalve and hoses from someone on the board for a very reasonable price if you want to set it up properly. I would be hesitant to just vent the tank as you described. Or, if the vented cap works and there is no smog inspection requirement then you could leave it like that. Just consider a rollover situation when making a decision and understand the risks.

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[stanwood]

No smog requirments since it's 27 years old. And I think even if it did roll over the 1/4 in hole in the can would only let it dribble out slowly. You should have seen the 30 gallons pour out underneath the hot engine when I initially started this issue! I ran a 100 yards and stood there for a while before I decided it was safe to return. I thought for sure it was going to blow. The tank was wedged under the exhaust. Guess that's why they make skid plates.