Yet another DFR question
Thread Starter
Junior Member
Joined: Oct 2012
Posts: 11
Likes: 0
From: Colorado Springs
Yet another DFR question
I have an '86 F150-302 with dual tanks. My problem is fuel (I would assume) is siphoning from the rear to the frt tank when it sits-the frt tank fills and the rear level drops. The DFR/electrical switch both switch properly and I can see the fuel gauge drop when either tank is used. It does not seem to be filling the frt tank when driving.
I replaced the filter in the DFR and as black as it was I bet it was the original. There was no debris in the cup. The filter in the fuel rail between the high pressure pump and injector rail was clean, the fuel came out looking good. I haven't taken the DFR apart as I'm hesitant to disassemble it without a replacement of some sort and I'd be afraid the seals inside would fall apart when they were disturbed. Fuel ran out while the cup was off-is this normal?
My question is: is this probably one of the valves in the DFR leaking/not sealing properly or is it tank pumps? Knowing my luck it's probably both. It also has an intermittent hard start after the 1st start cold, will start OK if the key is cycled a couple times-again pumps or DFR? I was wondering if there are ck valves in the pumps.
Sorry this is a little long but it's been driving me nuts trying to decide the best place to start.
Thanks for your help-I've found lots of helpful diagnostic info on Ford's quirky fuel system for these years.
I replaced the filter in the DFR and as black as it was I bet it was the original. There was no debris in the cup. The filter in the fuel rail between the high pressure pump and injector rail was clean, the fuel came out looking good. I haven't taken the DFR apart as I'm hesitant to disassemble it without a replacement of some sort and I'd be afraid the seals inside would fall apart when they were disturbed. Fuel ran out while the cup was off-is this normal?
My question is: is this probably one of the valves in the DFR leaking/not sealing properly or is it tank pumps? Knowing my luck it's probably both. It also has an intermittent hard start after the 1st start cold, will start OK if the key is cycled a couple times-again pumps or DFR? I was wondering if there are ck valves in the pumps.
Sorry this is a little long but it's been driving me nuts trying to decide the best place to start.
Thanks for your help-I've found lots of helpful diagnostic info on Ford's quirky fuel system for these years.
Senior Member
Joined: Feb 2009
Posts: 709
Likes: 31
From: Grants Pass, OR
I have an '86 F150-302 with dual tanks. My problem is fuel (I would assume) is siphoning from the rear to the frt tank when it sits-the frt tank fills and the rear level drops. The DFR/electrical switch both switch properly and I can see the fuel gauge drop when either tank is used. It does not seem to be filling the frt tank when driving.
I replaced the filter in the DFR and as black as it was I bet it was the original. There was no debris in the cup. The filter in the fuel rail between the high pressure pump and injector rail was clean, the fuel came out looking good. I haven't taken the DFR apart as I'm hesitant to disassemble it without a replacement of some sort and I'd be afraid the seals inside would fall apart when they were disturbed. Fuel ran out while the cup was off-is this normal?
My question is: is this probably one of the valves in the DFR leaking/not sealing properly or is it tank pumps? Knowing my luck it's probably both. It also has an intermittent hard start after the 1st start cold, will start OK if the key is cycled a couple times-again pumps or DFR? I was wondering if there are ck valves in the pumps.
Sorry this is a little long but it's been driving me nuts trying to decide the best place to start.
Thanks for your help-I've found lots of helpful diagnostic info on Ford's quirky fuel system for these years.
I replaced the filter in the DFR and as black as it was I bet it was the original. There was no debris in the cup. The filter in the fuel rail between the high pressure pump and injector rail was clean, the fuel came out looking good. I haven't taken the DFR apart as I'm hesitant to disassemble it without a replacement of some sort and I'd be afraid the seals inside would fall apart when they were disturbed. Fuel ran out while the cup was off-is this normal?
My question is: is this probably one of the valves in the DFR leaking/not sealing properly or is it tank pumps? Knowing my luck it's probably both. It also has an intermittent hard start after the 1st start cold, will start OK if the key is cycled a couple times-again pumps or DFR? I was wondering if there are ck valves in the pumps.
Sorry this is a little long but it's been driving me nuts trying to decide the best place to start.
Thanks for your help-I've found lots of helpful diagnostic info on Ford's quirky fuel system for these years.
Both in tank pumps must be operational in order for the DFR to work. The DFR is actuated by fuel pressure alone from the selected in-tank pump.
The in-tank motors and the gauges are independently switched by the dash switch so the gauges may switch when the pumps are not switching.
I gave up on the DFR system and installed an after market motor driven selector valve.
See my writeup.. Link in my signature...
Thread Starter
Junior Member
Joined: Oct 2012
Posts: 11
Likes: 0
From: Colorado Springs
I've looked at you setup-looks like it'll be more reliable. On mine both pumps work from the correct switch position and fuel returns to the proper tank when running, just siphons from rear to frt when it's sitting.
