Fuel Tank Selector Valve?

Hello,

The fuel switching valve is on the side of the frame rail here are instructions and diagrams to show you how to change it out. Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

Good afternoon,

The fuel switching valve by the rear tank is stuck open allowing fuel to transfer. It should allow fuel from one tank only to the front, not transferring. I attached the location of the valve and the description.

Roy

Hi,

I think I know what is happening. There is a fuel tank reservoir valve under the vehicle that is the likely problem. If you look under the driver's side door on the inside of the frame, there should be a black canister/fuel reservoir. See pic 1.

Check for that first. If it is there, you have two choices. You can purchase them on Amazon or eBay or you can try fixing the one you have.

What you will need to do is remove it from the vehicle, and remove the (I think 8) 10mm bolts from the top of it. When removed, there will be an orange diaphragm with one screw holding it in place. Remove the screw to expose a steel round plate. See pic 2.

I circled the part I am referring to in the pic. That is the item that determines if the front or rear tank is being used. Now, that steel plate can move up and down. When down, the front tank is being used. When down, the rear is used. What happens is the two steel slide rods attached to the round plate get dirty and no longer freely move up and down. As a result, fuel goes to different tanks when it shouldn't.

Take a good penetrating fluid and spray along the slides that hold the round plate and work it up and down until if feels free and moving smoothly.

Next, put it back together. Because there is fuel pressure in the reservoir, make sure to use a good sealant designed for fuel and heat when you reseal the top.

Let me know if you find it and if this helps. I've done it before because of the cost of replacement parts and it has worked fine. However, I can't guarantee it will do the job in all cases.

Take care,
Joe

Yours might not have a valve because it was a mid year shift. The reason the tank fills is because the check valve on the pump has gone bad. We used to replace both fuel pump assemblies when this happened which fixed the problem, but you may be able to locate the bad valve if you pull the front tank down. Here are the instructions in the diagrams below to help you fix the problem.

Fuel Pressure Check Valve Locations Components - COMPONENTS - Mounted on the In-Tank Fuel Pump.

You are welcome please let us know what you find. Use 2CarPros anytime, we are here to help. Please tell a friend.

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Use a voltmeter to check you are getting a hot feed to the pump .. did the shop replace the whole FDA unit or just the pump .. the sender unit handles the tank switching ?

Fuel Delivery Assembly (FDA)
The FDA consists of a fuel pump inside a reservoir that is attached to the pump and sender assembly. See Fig. 1 . In a 2-tank system, there is one FDA per tank. Fuel sender assembly handles the fuel switching through internal valves.
Fuel reservoir is used to prevent fuel flow interruptions during extreme vehicle maneuvers when fuel tank level is low. Reservoir is located in-tank and is either molded or welded into fuel tank or is part of FDA.
Shuttle valve opens fuel return line to fuel tank when fuel pressure on shuttle diaphragm exceeds opposing check valve spring force. When pump is de-energized, supply check valve closes to maintain pump prime and fuel supply line pressure.
A portion of high pressure flow from the pump is diverted to operate the venturi jet pump. The jet pump draws fuel from the tank into the FDA. This ensures adequate fuel supply during extreme vehicle maneuvers and steep vehicle attitudes when fuel level is low. If FDA is defective, it must be replaced as an assembly.

hope this help's

The return line is connected to both tanks. The only way to make sure it returns fuel only to the front tank would be to modify the return line so it only goes to the front tank. The system does not know the pump is bad as it does not monitor the pumps other than turning them on and watching the fuel pressure.

You would need to test the switch or check the fuel pump operations when you toggle the switch.

Poor acceleration should not be due to a bad switch. If it is due to lack of gas, it could be a clogged filter.

Checking the pressure will help with this.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

If the MIL is indicating, you need to get a scan done to retrieve the trouble codes and proceed from there.

Here is a guide that will help with this:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Let us know what you find. Thanks

FUEL DELIVERY
System Types
Electric fuel delivery systems differ in design depending on model. System designs use one of the following configurations:
Single tank with a single fuel pump.
Single tank with one Fuel Delivery Assembly (FDA). See Fig. 2 .
Dual tank with one FDA per tank.

Fuel Delivery Assembly (FDA)
The FDA consists of a fuel pump inside a reservoir that is attached to the pump and sender assembly. See Fig. 2 . In a 2-tank system there is one FDA per tank. Fuel sender assembly handles the fuel switching through internal valves.
Fuel reservoir is used to prevent fuel flow interruptions during extreme vehicle maneuvers when fuel tank level is low. Reservoir is located in-tank and is either molded or welded into fuel tank or is part of FDA.
Shuttle valve opens fuel return line to fuel tank when fuel pressure on shuttle diaphragm exceeds opposing check valve spring force. When pump is de-energized, supply check valve closes to maintain pump prime and fuel supply line pressure.
A portion of high pressure flow from the pump is diverted to operate the venturi jet pump. The jet pump draws fuel from the tank into the FDA. This ensures adequate fuel supply during extreme vehicle maneuvers and steep vehicle attitudes when fuel level is low. If FDA is defective, it must be replaced as an assembly.

See pic on how to diagnose this system. It's apdf file.

Hello, We had a truck in the shop the other day had the same problem, it ended up being the tank switching valve was bad, we replaced it and the problem was fixed. These valves are difficult to test or I would have you check it out.

Please let us know if this fixes your problem.

Best, Ken