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'93 F150 dual tanks not working

 
Old 08-30-2011, 10:16 AM
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Default '93 F150 dual tanks not working

I have a '93 F150 5.8L with dual tanks. When I flip the switch it just dies and wont start up until I switch it back to the rear tank. The fuel gauge will change when I flip the switch so I know its working but I don't know what is not working. Any ideas?
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Old 08-30-2011, 11:08 AM
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your pump is bad. replace the pump in the front tank and you'll be good to go.
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Old 08-30-2011, 11:22 AM
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Alright Thanks Is there any way to double check the fuel pump is bad before I replace it? I am a college student on limited funds so I just want to be sure before I replace it.
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Old 08-30-2011, 11:38 AM
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you can with the truck off switch to the front tank. then with the door open and head leaning out. or you under the truck with a friend at the key turn the key on BUT dont start the truck. you should hear the pump kick on and run for about 3 seconds.
that is the free check.
if the pump does not kick on turn off the key and hit the flat spot on the tank a few times pretty good. then try again.

but my experiance with these trucks 9 out of 10 times the pumps are junk and you have to replace them.
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Old 08-30-2011, 11:45 AM
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Thanks! I will give that a try before I buy a new pump.
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Old 08-30-2011, 12:45 PM
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Both fuel pumps are powered by the fuel pump relay but ensure there is voltage at the fuel pump connector anyway, before replacing the fuel pump. There is a 95% chance it is the fuel pump going out on those systems but you can never be too careful, rats get hungry too.

Be lucky the check valve hasn't went bad where one pump pumps all the fuel into the other tank and vice versa, that happened to my dad's truck. If I had to drop the fuel tank again, I would probably cut out a access panel with oxy/acy torch so it wouldn't have to be dropped ever again. That is, when every last drop of fuel has been eradicated completely, first!

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Old 08-30-2011, 12:49 PM
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Originally Posted by bluecar5556
Both fuel pumps are powered by the fuel pump relay but ensure there is voltage at the connector anyway, before replacing the fuel pump. There is a 95% chance it is the fuel pump(s) going out on those systems but you can never be too careful, rats get hungry too.

Be lucky the check valve hasn't went bad where one pump pumps all the fuel into the other tank and vice versa, that happened to my dad's truck.
The fact that he has a working fuel gauge on that tank, means he has power at that pump.
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Old 08-30-2011, 01:25 PM
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Originally Posted by kc0rey View Post
The fact that he has a working fuel gauge on that tank, means he has power at that pump.
Saying that a working fuel gauge means there is enough amps available at the fuel pump (requires several amps) is similar to saying working dash lights means there is enough amps to turn the starter.


Last edited by bluecar5556; 08-30-2011 at 01:38 PM.
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Old 08-30-2011, 02:23 PM
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Originally Posted by kc0rey

The fact that he has a working fuel gauge on that tank, means he has power at that pump.
Not so. When my switch went bad it could still operate the fuel gauge properly but wouldn't turn the pumps on.
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Old 08-30-2011, 02:37 PM
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The fuel tank selector switch is (2) DPDT switches linked together, one DPDT switches the fuel gauge sending unit and the other switches the fuel pumps, as illustrated above. Just because the fuel gauge switch from one rheostat to the other, does not mean the other fuel pump switch isn't worn or faulty that terminate at the fuel pumps. Makes sense, those contacts have to switch a several amp payload (fuel pump) vs. a very small current passing through a rheostat and energizing the windings inside the fuel gauge to move a very light armature.

This is why I am stressing to test the voltage at the fuel pump before replacing it. The fuel tank selector switch could have a bad contact, here.

Last edited by bluecar5556; 08-30-2011 at 02:46 PM.
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