89 F-250 Dual gas tanks


Senior Member
Central NJ 08620
I have an 89 F-250 with dual gas tanks. The rear tank leaked when I bought used it so had a new one put in along with a sending unit (i think).

Problem is when I switch tanks from front to back, the gas gauge will go to full, which the tank is, but there is no actual switchover between the tanks. The fuel keeps flowing only from the front tank.

I have also replaced the switch hoping that for some reason that was the problem. On occasion since then, when switched to the rear tank, it will run for a while then start to cough and die out.

Any suggestions??



PlowSite.com Veteran
I had an 88 that had crazy gas gauges too (but at least switched over to the proper tank). Just a shot in the dark, is it possible that the fuse that powers the sending unit is popped ? I know there is a fuel cut-off circuit up under the dash, but I think that would kill both tanks, but there must be fuses that power each of the units too. Just a guess.

Jerre Heyer

Senior Member
Erie, PA
Check your 88 . You put a sending unit in but did it have an in tank fuel pump??

Yes-- Check fuse box(es) for fuse may be one for each tank. Also check the plug in connector at the tank to see that you are getting power to the pump and also a good ground.

No-- Ford used a unit on the drivers side frame rail to switch which tank the fuel was pulled from. Two lines coming in and one out. Located usually inside the frame rail right below the drivers door/ cab corner are. This unit can be a real pain when it starts to act up.

I had one that pulled from both tanks at the same time. Fuel guage read E and both tanks were dry when I flipped the switch. Not a nice suprise when out late at nite. The ultimate I ran out of gas............I was on a date.

Good luck Jerre


PlowSite.com Veteran
My 88, (now gone) I ended up just using the trip odometer. I knew at x miles it was time to fill up. The 88 would go for periods of time working fine, then do the full -> empty in 1 mile trick to me. Fortunately, never ran out.

Sorry for the distraction, that doesn't help CMerLand.


2000 Club Member
There are a number of things which could cause this, you'll have to eliminate them one by one.

1. Make sure you have power at the switch, as has been suggested. If this is OK,

2. Check that both leads going to the switching valve have power at the valve.

3. Check that the valve is functioning. You'll have to disconnect the hoses and I'd use low pressure compressed air to check that the valve is switching when activated.

4. Verify where your fuel pump(s) are, if you have one pump between the valve and the engine, the pump's OK. If there are two pumps, verify that the rear has power and is working.

If it's a one pump system, a rust hole in the rear fuel line could cause this problem, check on this.
Owosso, MI
Don't know if you got the problem fixed or not just happened to read the problem. I have a 85 f250 with dual tanks and had the same problem except with the front tank, replaced the fuel selector switch, still had the problem, what I found was that on the sending unit in the top of the tank that the tit where the fuel line hooked up to was rusted and had pit holes in it so when I switched tanks it would use up the gas in the line then it would suck air instead of gas from the front tank. I ended up cutting the tit back and reinstalling the gas line (quick fix ) but it worked for now until I can drop the tank to have a new tit brazed on. Hope this helps if you haven't found the problem already.


Junior Member
Eastern KY
I have an 89 F150 that has the same problom. The gas gage works but it fails to keep the engine running. I can fill both tanks and leave the switch on the front tank and it will run on both tanks at the same time. I have also noticed that when I fill the front tank, instead of kicking the gas pump off if will let gas bleed back to the back tank. Anyway, there is a valve located on the inside of the frame under the drivers door, it has four gas lines going in( 2 return & 2 main lines) and two lines coming out the other side. That could very well be your problom. I bought one at a junkyard for about $30, but I haven't had time to put it on. On my truck this is the last fuel component that I havent checked or changed.

I hope this helps.

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