1986 fuel tank problems
10-09-2009, 06:57 PM
#1
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1986 fuel tank problems
have a 1986 f150 302 fuel injected supercab. my question is can fuel go from one tank to another? it seems to be going from the rear to the front. when on the front tank it seems to run rough some times. not all the time. runs great on the rear. can it be sucking air some how?
10-09-2009, 11:09 PM
#2
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The fuel selector is most likely the problem. It's located on the frame rail near drivers seat:
http://i608.photobucket.com/albums/t...ordfuelres.jpg
The selector is supposed to switch the return fuel lines to the selected tank. The in-tank pump motors are switched by the dash switch, however the selector works by fuel pressure alone from the running in-tank pump.
If gummed up or broken or just warn out, fuel will be returned to the wrong tank or both tanks at the same time depending on what is broken.
In my case a bad pump/sender in my rear tank allowed bits and pieces of junk to pass which plugged everything up.
I ended up replacing my selector with an electric motor actuated tank selector switch. also added inline filters from each tank.
http://i608.photobucket.com/albums/t...ordfuelres.jpg
The selector is supposed to switch the return fuel lines to the selected tank. The in-tank pump motors are switched by the dash switch, however the selector works by fuel pressure alone from the running in-tank pump.
If gummed up or broken or just warn out, fuel will be returned to the wrong tank or both tanks at the same time depending on what is broken.
In my case a bad pump/sender in my rear tank allowed bits and pieces of junk to pass which plugged everything up.
I ended up replacing my selector with an electric motor actuated tank selector switch. also added inline filters from each tank.
10-10-2009, 10:36 AM
#4
Senior Member
Looks like it can be re-built IF you can get the parts? I have no idea if parts are available? This would be a dealer item.
You can get the lower reservoir filter at any autoparts store.
I looked inside mine and did manage to get it unstuck and working (bench test) but the parts looked warn. Had so much trouble with it in the past so I gave up and installed a different selector.
Here is what the original selector looks like on the inside (not mine).
http://i608.photobucket.com/albums/t...s/FUELRES2.gif
The 2 'star' retainers come out and the plungers and parts come out.
You can get the lower reservoir filter at any autoparts store.
I looked inside mine and did manage to get it unstuck and working (bench test) but the parts looked warn. Had so much trouble with it in the past so I gave up and installed a different selector.
Here is what the original selector looks like on the inside (not mine).
http://i608.photobucket.com/albums/t...s/FUELRES2.gif
The 2 'star' retainers come out and the plungers and parts come out.
10-11-2009, 02:17 PM
#6
Senior Member
I removed the top cover by taking out all the screws.
I blew air through the tank return ports and actuated the valve by pressing the diaphragm disk. The diaphragm is rubber with a metal disk attached (~3" diameter), not shown in the photo. The disk is mounted between the top cover and the valve chamber that you see in the photo.
If operating properly then one tank return port will be open and the other closed off. They will switch the other way when the plunger is moved.
I don't know if this will completely test all functions? My unit was stuck in one position at first but I was able to clean things up got it working somewhat but never put it back on the truck and tried it.
I blew air through the tank return ports and actuated the valve by pressing the diaphragm disk. The diaphragm is rubber with a metal disk attached (~3" diameter), not shown in the photo. The disk is mounted between the top cover and the valve chamber that you see in the photo.
If operating properly then one tank return port will be open and the other closed off. They will switch the other way when the plunger is moved.
I don't know if this will completely test all functions? My unit was stuck in one position at first but I was able to clean things up got it working somewhat but never put it back on the truck and tried it.
10-15-2009, 08:52 PM
#7
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ok i changed out the fuel selector valve with a new one. my question is the in tank fuel pump. can it operate sometimes and sometimes not? it will still sputter sometimes on the front tank; rear runs great.
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10-15-2009, 10:50 PM
#8
Senior Member
A tank pump may not be working and the engine can still run. Listen to the high pressure pump as you select between the 2 tank pumps. If you hear the high pressure pump begin to strain or change pitch then that tank pump may not be working correctly.
The photo below shows a sender unit. The silver can is the pump.
Notice the black rubber hose between the pump and metal tube. If that rubber hose has a hole in it, then that may cause what you are describing. May act differently depending on the fuel level in the tank.
In my case that entire rubber hose had disintegrated into a pile of sludge in the bottom of my tank. The pump was also jammed up with gunk.
Sender unit:
http://contentinfo.autozone.com/znet...2093S/image/8/
The photo below shows a sender unit. The silver can is the pump.
Notice the black rubber hose between the pump and metal tube. If that rubber hose has a hole in it, then that may cause what you are describing. May act differently depending on the fuel level in the tank.
In my case that entire rubber hose had disintegrated into a pile of sludge in the bottom of my tank. The pump was also jammed up with gunk.
Sender unit:
http://contentinfo.autozone.com/znet...2093S/image/8/
10-16-2009, 09:52 AM
#10
Senior Member
Not that hard to get the tank down. Hardest thing for me was the bolts on the skid plate. I think the front tank has a strap. The rear did not.
You will need let the tank down some on a jack or something until you can reach the connections. Remove the electrical connector, fuel lines, filler hose and air bleed line then drop it down the rest of the way.
I cleaned and reused the check valve. Bought a new 'donut' gasket at the dealer for $6.
I had planned on just cleaning my tank and tried for days, but gave up and bought a brand new tank for $100 at Autozone. There was lots of rust and thick tar like deposits in the tank. Not sure but the new tank seamed slightly less thick than the original.
You can have the tank professionally cleaned and treated if you can find someone who still does that. There are also DIY tank restoration kits you can get but they cost about as much as a new tank.
I bought a new sender with pump for $120.00 also from Autozone. You can buy just the sender or just the pump alone.
You will need let the tank down some on a jack or something until you can reach the connections. Remove the electrical connector, fuel lines, filler hose and air bleed line then drop it down the rest of the way.
I cleaned and reused the check valve. Bought a new 'donut' gasket at the dealer for $6.
I had planned on just cleaning my tank and tried for days, but gave up and bought a brand new tank for $100 at Autozone. There was lots of rust and thick tar like deposits in the tank. Not sure but the new tank seamed slightly less thick than the original.
You can have the tank professionally cleaned and treated if you can find someone who still does that. There are also DIY tank restoration kits you can get but they cost about as much as a new tank.
I bought a new sender with pump for $120.00 also from Autozone. You can buy just the sender or just the pump alone.
