1987 Ford F-250 fuel transfer issue
#1
1987 Ford F-250 fuel transfer issue
So I believe I am having an issue with my fuel tanks where when I switch the tanks from rear to front, the front is not pushing fuel to the engine. What might be causing this? I was driving down the road and the truck just died when I was the full front tank, electronics still worked, but lost power steering and the engine turned off. Any ideas? It's a 6.9 diesel with a switch on the dash up front
#2
This is a common problem with gas fueled trucks of this vintage. Check the fuel pressure coming from the front tank - its fuel pump is probably DOA, or the fuel switchover valve/reservoir is DOA and not switching properly.
The gas fueled truck have three pumps - one low-pressure in each tank and one high-pressure on the frame.
Don't know if same is true of diesel.
The gas fueled truck have three pumps - one low-pressure in each tank and one high-pressure on the frame.
Don't know if same is true of diesel.
#3
under the door located inside the frame you will see a canister looking fuel filter then going back the main high pressure pump then further back next in line is the vacuum diaphragm fuel tank diversion valve, this is actuated totally on pressure created from the chosen fuel tank pump. This is retaliative to both fuel systems. The diaphragm inside becomes Dirty or develops pin holes and will not allow the pressure from the chosen tank to switch the inlet fuel line.. the best way to check this system is have your friend sit in your truck while you crawl under your truck and listen for the chosen tank pump to run...
#1. with the key off select the front tank. now hold a wooden dowel on the forward tank and place the other end of the dowel in the inner joint of your thumb now jamb your thumb knuckle in your best ear and have your buddy turn on the ignition key ( do not start the engine) tank pumps begin to build pressure immediately.
#2. If no noise is noticed from forward tank repeat this same procedure for the rear tank. making sure to turn off the ignition before selector switch is changed and the test is started
#3. If noise from pump run is noticed in the rear tank you have three possibilities.
(A) the forward tank connection on the selector switch is corroded or not making contact. check connection under dash. I have seen wires pulled out of the wire connection plug offering the problem you have.
(B) your forward tank fuel pump has a possible wire loose on the loom on top of the tank. check connections this can be done with out removing the tank just takes some wiggling your arm on top of the tank.
(C) your forward tank pump has expired. replacing pump requires removing the tank, your pump is on the bottom of the sending unit Dorman makes a kit that includes the retainer ring that hold the sending unit secure in the tank,, i recommend it when replacing the pump or the sending unit
#3. if fuel from a full tank is being pumped back and filling the opposite tank being used your problem is vacuum switch valve located inside the frame rail behind the high pressure fuel pump.... parts geek sells a affordable alternative to the factory junk switch.. this is what you would be replacing
#1. with the key off select the front tank. now hold a wooden dowel on the forward tank and place the other end of the dowel in the inner joint of your thumb now jamb your thumb knuckle in your best ear and have your buddy turn on the ignition key ( do not start the engine) tank pumps begin to build pressure immediately.
#2. If no noise is noticed from forward tank repeat this same procedure for the rear tank. making sure to turn off the ignition before selector switch is changed and the test is started
#3. If noise from pump run is noticed in the rear tank you have three possibilities.
(A) the forward tank connection on the selector switch is corroded or not making contact. check connection under dash. I have seen wires pulled out of the wire connection plug offering the problem you have.
(B) your forward tank fuel pump has a possible wire loose on the loom on top of the tank. check connections this can be done with out removing the tank just takes some wiggling your arm on top of the tank.
(C) your forward tank pump has expired. replacing pump requires removing the tank, your pump is on the bottom of the sending unit Dorman makes a kit that includes the retainer ring that hold the sending unit secure in the tank,, i recommend it when replacing the pump or the sending unit
#3. if fuel from a full tank is being pumped back and filling the opposite tank being used your problem is vacuum switch valve located inside the frame rail behind the high pressure fuel pump.... parts geek sells a affordable alternative to the factory junk switch.. this is what you would be replacing
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