Overflowing R/H Gas Tank 87 XJ6 4.2 Liter Fuel Inj

[Michael J.]

I have had the 87 XJ6 with 173,000 miles for just over one month now.

When I bought the car, the prior owner told me that he was having a problem with the tank change-over system.

I filled both tanks to check it out. The fuel tank selector switch was in the <font color="red"> </font> "out" <font color="black"> </font> position. The prior owner had a small plastic tube stuck in the left cap keeping the flapper valve open and keeping the fuel cap spring loaded seal from seating. He was using only the left tank and kept the right tank empty.

I bought and installed a change-over valve kit. The kit included the two non-return valves, one in each wheel well and the changeover valve in the trunk at the rear near the fuel pump.

The non-return valves have two wires color-coded white and black.

But, is it possible to cross the wires for the change-over valve? I was careful to collect the wires the same way as the valve being replaced.

I filled both tanks, presuming that the problem was solved. I drove for a few days with the tank selector switch pushed "in". When the tank was almost empty, I released the switch to the "out" position. A short time later, I had gas comming up out of the right tank, a lot of it, pushing up the spring loaded valve and overflowing down the fender onto the ground.

<font color="red"> </font> With the switch in the out position, Which tank is supposed to be the supply tank?

Any other suggestions? <font color="black"> </font>

The scematic diagram for the fuel system on page 19-2 of the Series III Service Manual appears to have some errors in which the non-return valves in the text are both referred to as the change-over valve and the change-over valve is not numbered or mentioned, although depicted on the schematic.

Should I swap the wires at the change-over valve? Is there something else to check?

 

[jessebogan]

In is left tank, out is right. - The non return valves are handed. Make sure that they are exactly like the ones you removed. Find a bright spot, and run the car with the fillers open. You should see the fuel returning through the filler openings. Use a thin screwdriver to push the flap out of the way. Fuel should only return to the tank selected. If this is not the case, it is time to electically check the fuel return valves. I think that the harness that connects to the non return valves is a link harness, and connects behind the gas tank cover under the rear bumper. HTH

 

[Michael J.]

The Cross-over valve kit was from Welsh Enterprises and they had each of the non-return valves clearly marked and the flow direction arrow on each valve was pointing in the same direction as the valve removed.

I will check the flow as you suggested and report back.

 

[John S Farrington]

The situation that overflowed the right tank was brought on by the following: The switch out position should select the right tank (main tank) via the trunk changeover valve. The selector out position will also close the left return valve and open the right return valve. In order to have the overflow the right return valve was correctly letting return fuel go the the right tank. However the crossover valve had to stay in the left tank position. That caused the full right tank to have return but not draw with the result that it severely overflowed. In trouble shooting as to why this happened, remember that the fuel selecter switch can develop errors and give erroneous results with correct switches in the system. I recommend that you create a schematic of the fuel switches and valves from the main system wiring diagram in order to assist your trouble shooting. It is a good assumnption that your three valves are correct but there is a fault either in the selector switch or the wiring going from it to the valves. With an ohmmeter/voltmeter you can verify the operation of the fuel delivery system. Pay particular attention to wire color coding. (white and black) As I remember, The three valves are signaled to open or close by the presence of 12 volts and ground. In the case of the cross over valve, it toggles from one tank to the other. If the 12 volts is not present they default to the opposite position. Hope this helps. Jack

 

[Michael J.]

I checked the fuel flow with both caps open as suggested and with the engine running. With just the ignition on, there did not seem to be any fuel flow to either tank.

I did not see any flow at all returning to the left tank with the switch in or out at any time. With the switch in, I did not see any return to the right tank either. Where is the excess fuel going when the switch is in?

I pumped about 2 gallons from the right tank into a gas can. With the switch "out", there is a LOT of fuel flow, so much so that the tank overflowed again, in less than 2 minutes!

Where did the gas come from? The left tank has only about two or three gallons in it. How much fuel has to be in a tank before there is a fuel return?

What about the air bleed valve located near the fuel filter? Can it malfunction?

 

[Michael J.]

Jack, I will start on the wiring diagram and checking for voltage for each valve as well.

 

[Michael J.]

I changed out the air bleed part that screws into one side of the hex shaped fuel block that has the CAC 2027 Fuel Non Return Valve. I am not seeing fuel spewing onto the flapper at the r/h cap at it had been.

If I fill the left tank and keep the switch in to operate off the left tank, I have no problem. I switch to the r/h tank only when fuel is less than 1/4 tank on the left tank, or if there is enough room in the r/h tank to take everything in the left tank. Fuel still transfers, but much more slowly.