Dual Tank Question
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Dual Tank Question
Ok I have a 1989 F150 5.0L with dual tanks. Now when you use the tanks does the front tank have to be empty to use the rear. Cause everytime I switch it to the rear the needle never mooves and when I switch it back to the front the needle is closer to empty then when I used it last. I know the rear works cause I have filled It before but that was a while back.
Senior Member
Joined: Aug 2000
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From: Lockport, NY USA
You can switch back and forth between tanks at any time. There was a recall at one time for a fuel check valve, i believe the problem was fuel from one tank would get sucked into the other. I don't know the specifics of it but im pretty sure the recall is expired so you would be fully responsible for whatever repairs are needed. I'm sure someone else on here will chime in with some better info.
-Jon
-Jon
Senior Member
Joined: Aug 2006
Posts: 614
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From: Troy, NY
No, the two tanks work independently of each other. They have seperate fuel pumps to supply the hi-pressure injectors. There was an issue in some models where the over-pressure line that flows back to the tanks was defective and only fed to one tank, so it's possible running off one tank actually slightly filled the other.
An easy way to check the tanks is to turn the key to ON, but don't start the motor. Set the switch to front, and you should hear a fairly loud whirr from under the cab. Turn the key off, switch it to rear, and back on again. You should hear a fainter whirr from the rear of the bed. If you don't, then one of the fuel pumps isn't operational.
As for the needle not moving, the fuel sensor could be defecive. If the gauge doesn't get a signal, it just doesn't move at all, it won't drop to nothing. That's why when you shut the key off the temp gauge doesn't move until you re-start it.
An easy way to check the tanks is to turn the key to ON, but don't start the motor. Set the switch to front, and you should hear a fairly loud whirr from under the cab. Turn the key off, switch it to rear, and back on again. You should hear a fainter whirr from the rear of the bed. If you don't, then one of the fuel pumps isn't operational.
As for the needle not moving, the fuel sensor could be defecive. If the gauge doesn't get a signal, it just doesn't move at all, it won't drop to nothing. That's why when you shut the key off the temp gauge doesn't move until you re-start it.
Senior Member
Joined: Jun 2005
Posts: 639
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From: Easton, Kansas
You may have a bad sending unit in the front tank.
The check valve that Ford4ever posted about was for the 1993 in-tank pump and your check valve is in the Hi-Pressure pump on the frame, in short you have a different fuel system.
The sound that RaWarrior posted about will a little hard for you to hear, as the Hi-Pressure pump on the frame will run with either tank selected. You would have to listen at the filler neck of each tank to hear if the in tank is running.
Here is a diagram of your fuel system:
http://i54.photobucket.com/albums/g9...Fuelsystem.gif
Hers is electrical diagram of you gauge system, wire colors may differ.
http://i54.photobucket.com/albums/g9...el/88fuels.gif
The check valve that Ford4ever posted about was for the 1993 in-tank pump and your check valve is in the Hi-Pressure pump on the frame, in short you have a different fuel system.
The sound that RaWarrior posted about will a little hard for you to hear, as the Hi-Pressure pump on the frame will run with either tank selected. You would have to listen at the filler neck of each tank to hear if the in tank is running.
Here is a diagram of your fuel system:
http://i54.photobucket.com/albums/g9...Fuelsystem.gif
Hers is electrical diagram of you gauge system, wire colors may differ.
http://i54.photobucket.com/albums/g9...el/88fuels.gif
