Cant change tanks

That is normally located on the engine right where the fuel line comes in. It should not be affected by a second tank.

Check your fuel pump in the front tank. The fact that it begins to stall - tells me that the valve is actually working - the front fuel pump just isn't pump fuel.

If you're doing it yourself, what you do is find a good spot to park it where you can wiggle under it and you crawl around and find the leak. You're going to be under there for a few minutes so make it a comfortable spot.

If the truck leaks all the time, running or shut off, then you'll find the leak at a level lower than the tank or in the tank itself.
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If it only leaks when running then it's going to be a fuel line, the valve that switches tanks (likely) the lines coming out of the tank (also likely) or under the hood somewhere. Find the wet spot and look up from there, that's how you start. Maybe the leak isn't obvious, if it's dripping off the frame or a crossmember then you have to look around and see where it's coming from. If it's dripping off the tank, only when the fuel is being pumped, then you'll find rotten steel lines coming out of the top of the tank.

With a truck of this age, you can solve a lot of current and future problems by buying enough 3/16" or 1/4" fuel hose and just replacing all the fuel line between the tank and the motor. Zip-tie it to the frame as you go, don't pinch it hard- just enough that it can't move and wear a hole in the hose. Keep the hose where it's safe from road debris- on the top rear of crossmembers and tucked back into the lower corner of the frame rails.

lp

Hi:
You might have two seperate problems:

If fuel is draining from the rear tank to the front, there is a tank shuttle valve located on the drivers side frame rail that is the most likely suspect to fix that.
It costs around $120 or so, and when it fails, you get that siphoning going on, and often the front tank wont pump at all.
In your case, if the engine is running rough off the front tank, you might have another issue, such as a bad in tank fuel pump, but the shuttle valve needs changed first , so maybe it might fix the other problem too!

If the gauge works on the rear tank but not the front, the problem is most likely the sending unit in the front tank. You will have to drop the tank to change it. I guess what I would do is, set your trip meter to zero when you fill the front tank. Then, run that tank to the point where the truck is starting to run out of gas and then switch to rear tank. Keep track of how far you can go on the front tank. Then when you refill the front tank reset the trip meter and switch tanks about 20 miles before you think it's going to run out. It's not a good idea to run those pumps dry. Just make sure you have gas in the rear tank. If you do decide to change the sending unit, run that front tank as empty as you can, also, I would change the pump too. In 92, I think the pump or the sending unit can be replaced seperately. The worst thing about changing those in tank fuel pumps is getting the gas out of the tank. No trip meter? Just write down the mileage from the odometer. Good luck.

there is a special tool to do this, but I just use a giant pair of channel locks

your tank os on the right side standing in front of your car,it's the bottle and your radiator is in front of the engine,it looks like a bunch of black finns.

Hello bilsher...The La Crosse does not have a serviceable fuel filter. It has a strainer that is located in the tank... but there is no maintenance required for the fuel system.
Hope this answers your question.... please rate me a fixya.

I could be wrong but I thought it was in the engine compartment by the fire wall. If not find the fuel line going to fuel rail on intake and follow it back. There were a few cars they put them in the front fender. but follow the line from front back to the tank you will find it.

The tank selection device is located in the frame, it is expensive and is probably your culprit. It is has valves which open and close as you switch tanks. It should have blocked the line to back tank as it changed to front tank.