Fuel pump info?
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Cargo Master
Joined: Sep 2006
Posts: 2,120
Likes: 390
From: Evansville, Indiana
Fuel pump info?
My '86 F150 302 EFI has two fuel tanks. Recently the guage quit working for the rear tank. Also it gets a running out of gas vibe sometimes when it is running on the rear tank. This goes away when I switch to the front tank. There is a fuel pump om the frame rail under the cab on the driver's side. Also a canister type fuel filter.
I was told that my truck may have a fuel pump inside each tank as well. (info not from a reliable sorce)
However, since the poor performance when operating on the rear tank coinsided with the failure of the gas guage, I thought this extra fuel pump could be possible. Perhaps a bad ground could cause both to fail simultaneously?
I figure someone here knows for a fact about the fuel pump or pumps.
I am replacing the fuel filter now.
I was told that my truck may have a fuel pump inside each tank as well. (info not from a reliable sorce)
However, since the poor performance when operating on the rear tank coinsided with the failure of the gas guage, I thought this extra fuel pump could be possible. Perhaps a bad ground could cause both to fail simultaneously?
I figure someone here knows for a fact about the fuel pump or pumps.
I am replacing the fuel filter now.
Elder User
Joined: Nov 2004
Posts: 666
Likes: 5
I have no personal experience with the '86, but according to Autozone, there is a fuel pump in each tank plus the external pump on the frame. If your rear level sender does not work and performance is bad when using the rear tank, it is possibly a ground problem. The in-tank fuel pump in mounted on the sending/pickup unit.
Looking at the pictures on the Autozone page, it looks like the sender has a 4 conductor plug: 2 wires going to the pump, one to the sender, and the other may be ground for the sender. I don't know about the wiring outside of the tank. It is possible that the sender ground wire and the pump ground wire go to a common ground point, and that may be corroded or broken. I would start by following the wiring from the sender to see if one or two wires go to the frame somewhere near the tank and check that connection.
Sorry I can't offer any first-hand experience on this one.
Looking at the pictures on the Autozone page, it looks like the sender has a 4 conductor plug: 2 wires going to the pump, one to the sender, and the other may be ground for the sender. I don't know about the wiring outside of the tank. It is possible that the sender ground wire and the pump ground wire go to a common ground point, and that may be corroded or broken. I would start by following the wiring from the sender to see if one or two wires go to the frame somewhere near the tank and check that connection.
Sorry I can't offer any first-hand experience on this one.
Freshman User
Joined: Dec 2005
Posts: 28
Likes: 0
From: Wheatland, Ca
yes the 86 have two low pressure pumps in each tank, they the m flow through the 6 port fuel reservoir (this switches the return line fuel to the correct tank) from the switch to the high pressure pump on the frame rail. when you fir turn the key on you should be able t o hear that tank run. this might take to people one turning the key the other listening at the tank. another good check is disconnect the the 3/8 line going to the 6 port switch. have some one turn the key and see if you are getting good fuel pressure.( i hope i don't have to explain the dangers of gas and fumes and ignition sources) i found that my switch was stuck if i by passed the switch using 3/8 inch fuel line to tthe high pressure pump everything worked great.
Thread Starter
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Cargo Master
Joined: Sep 2006
Posts: 2,120
Likes: 390
From: Evansville, Indiana
Thanks Jim and JD for the leads. I tried but failed to run down a wiring diagram today. Our library has a repair manual with a good one. Someone else must have it checked out.
Also, when I changed the fuel filter (cannister type) there were tiny white bits of something in the cap. Not a lot but this is the first time I've ever seen anything that looked like a contaminant come out during a filter change.
Also, when I changed the fuel filter (cannister type) there were tiny white bits of something in the cap. Not a lot but this is the first time I've ever seen anything that looked like a contaminant come out during a filter change.
Freshman User
Joined: Dec 2005
Posts: 28
Likes: 0
From: Wheatland, Ca
