Unusable Fuel in Tank

This is not an uncommon Grand Wagoneer complaint, but needs troubleshooting.

And a properly functioning GW fuel system, despite what the mechanic told you, will not normally run out of gas at 1/4 tank even on a curve.

First you have to do basic stuff- the tank has a volume of ~20.3 U.S. gallons. Do something like this. Carry a 5 gallon can of gas around town with you and do errands near gas stations until it runs out of gas. Check the indicated fuel level on the gauge then fill with the 5 gallons and go to a nearby gas station and fill the rest of the way. Do the arithmetic and figure how much gas was really in the tank when it ran out. If it really runs out at 1/4 tank full then there is a fuel delivery problem. If it was really empty at 1/4 tank indicated, then it is a bad sender, bad gauge, bad wiring or connections. I would also say, do NOT do as some recommend and try to correct any of these problems by putting resistors in the circuit. I just think this is a bad approach to addressing a problem with a component, and is likely to confuse you or someone else in the future.

The reason a GW should not "run out of gas" on a curve or otherwise when the level is low is because the tip of the fuel pickup on the sender is positioned in a well in the tank. Unless on extreme inclines with very little fuel, the pickup should remain immersed.

The problems I can think of that can mimic an out-of-fuel condition are as follows:

1. Clogged in-tank fuel filter sock
2. Replacement sender with incorrect short pickup tube
3. Upside down fuel filter with the vapor nipple at 6:00
4. Clogged gas tank vent (normally runs back to the charcoal cannister)
5. Bad vent check valve
6. Weak fuel pump.

If venting is the problem, removing the gas cap when you seem to run out of gas should let the engine start again.

Be aware that the sender (and the vent check-valve) can be checked or changed out without dropping the tank using the access panel on the driver's side of the cargo area (back seat folded forward). It is under the carpet and may be riveted, but the rivets can be easily drilled out and then replaced with sheet metal screws when you are done.

"If needed, BJ's Off-Road has the senders and socks (which should be attached to the pickup tube with a hose clamp).

Your GW did not "run out of gas" at 1/4 tank when new, so if repaired properly, there is no reason for it to do so now to do so now.

Thanks for this very informative response. I will work on doing this and get the fuel system back to normal, as my GW only gets about 8.8 mpg, I sometimes need all the fuel in the tank!

In reference to the fuel filter vapor nipple, are you referring to the inline fuel filter in the engine compartment?

I'll look into it. Does the float and sender sit under the access panel, or do I need to drop the tank to check this?

Thanks, Bill.