93 F150 Fuel Always Returns to Rear Tank
#1
93 F150 Fuel Always Returns to Rear Tank
When the tank selector is in rear, fuel returns to the rear tank as expected. When the front tank is selected, it slowly fills up the rear tank but may be also returning to the front tank. My question is that since I don't see a valve under the truck, the in tank fuel pump must have a valve in it that selects the return meaning that the rear tank valve is stuck open. Correct? Is there a way to repair this or is it a fuel pump replacement project?
#5
Originally Posted by bluesman2333
When the tank selector is in rear, fuel returns to the rear tank as expected. When the front tank is selected, it slowly fills up the rear tank but may be also returning to the front tank. My question is that since I don't see a valve under the truck, the in tank fuel pump must have a valve in it that selects the return meaning that the rear tank valve is stuck open. Correct? Is there a way to repair this or is it a fuel pump replacement project?
EDIT:
On a 1993 you need to check the FPR (Fuel Pressure Regulator) also as they had a lot of bad ones that year and the FPR will take out these valves.
Last edited by subford; 02-02-2008 at 07:07 AM.
#7
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#8
You have two valves in the FDM. One is the hi pressure check valve that prevents gas from entering the tank from the other fuel pump and hold the fuel pressure after you turn off the key.
The other valve is the shuttle valve and it prevents gas from entering the tank from the fuel pressure regulator when the other fuel pump is running.
The extra hi pressure check valve out side the tank will only work if the hi pressure check valve is bad but will do nothing for you if the shuttle valve is bad.
The FDM.
/
The other valve is the shuttle valve and it prevents gas from entering the tank from the fuel pressure regulator when the other fuel pump is running.
The extra hi pressure check valve out side the tank will only work if the hi pressure check valve is bad but will do nothing for you if the shuttle valve is bad.
The FDM.
/
Last edited by subford; 02-02-2008 at 06:58 PM.
#9
Ah right! I can compare the fuel pressure bleed off between the two tanks to see if the check is bad. If that is OK, then it's the shuttle valve by default. From the pictures on autozone.com, it looks like the fuel pump assy must contain everything including the shuttle valve, so it must not be a separate item. As far as repairs go, this 150.00 won't be the most expensive one recently!
#10
Originally Posted by bluesman2333
Ah right! I can compare the fuel pressure bleed off between the two tanks to see if the check is bad.
Originally Posted by bluesman2333
If that is OK, then it's the shuttle valve by default. From the pictures on autozone.com, it looks like the fuel pump assy must contain everything including the shuttle valve, so it must not be a separate item. As far as repairs go, this 150.00 won't be the most expensive one recently!
Example of one brand that autozone sells.
/
Last edited by subford; 02-02-2008 at 09:48 PM.
#12
#13
Originally Posted by bluesman2333
@subford, forgot about the fact that you need the pump running.
You said you can compare the fuel pressure bleed off between the two tanks and you can not do that with them "T"ed together.
With the lines "T"ed when you shut off the rear pump and the pressure holds you have a bad shuttle valve and if not you have a bad check valve.
And you can only do this if the FDM is 100% OK in the front tank.
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