Questionhi mr howard is there any way to bypass those fuel return valvs on 85 xj6 jaguar. if so please let me kno// and what do i have to do to do so. my valvs work when i check them on battery but it seem like not enough fire when thay/r on car test lite works fine when i check for fire. thanks.
AnswerHi James,
To bypass the use of the return valves is easy. All you need to do is to ONLY use the left tank. NEVER use the right tank. To use both tanks without the use of the return valves you will need to carry an experienced flight engineer to transfer fuel when needed and manage your fuel supply or you will be continuously overflowing one or the other tank by transferring fuel when you shouldn't.
Since the valves are good, the far easier job would be to just fix the wiring. All you need is a good wiring diagram, a 12v test light, a volt meter and a long piece of 14 gauge wire to use as a test lead. If you don't have a good diagram, let me know and I will post one on my web site for you to copy.
First lay out your diagram and this set of instructions in front of you at the car. Turn the ignition on and turn the left tank on and confirm the left tank gauge reading as what you think is the fuel level in the left tank. Go to trunk (boot)and remove the spare tire (tyre) and test the White w/Purple tracer wire at the fuel switching valve. (TEST IT WITH YOUR VOLT METER) You should see -0- volts. Now, remove both rear tires (tyres) and remove the lower return valve panels and test BOTH return valve power wires with a VOLT meter. Here again you should see -0- volts at both valves.
Now switch to the right tank and read the fuel gauge to see if it has the amount of fuel that you believe is in the right tank. Go to the fuel supply switching valve and test the White w/Purple tracer wire for voltage. You should see close to battery voltage. Now have someone else switch from right to left and back to right tank while you put your finger on the valve and note if you feel it "Click" and hear it "Click".
With the switch in the "right" tank position, if you did have voltage but could not feel nor hear a "Click" in the valve, test the Black wire for voltage. If there "IS" voltage, you have a bad ground.
Now go to each return valve and run the exact same test as the fuel supply switching valve test that you just did.
When you do voltage tests with a volt meter or even a 12v test light, you need to do it with the "Load" on it. Meaning the item that is powered. The three valves here are just solenoids and do draw some amperage and when under load can show a voltage drop. With good connections that drop in voltage will be minor. However if you have a bad connection, you will see a voltage drop that would not be noted if you had disconnected the solenoid and tested the wire for power. For example, a mechanic can disconnect a wire from a solenoid and turn on the power and test it for voltage and see a full battery voltage. Then connect up the a known good solenoid and finds that it don't operate. He then tests the voltage with the solenoid connected and sees a very low voltage. This shows a bad connection in the power "OR" the ground circuit. A poor connection in the power side of the solenoid (load) shows up as a low voltage and a poor ground shows up as any voltage on the ground side of the solenoid.
let me know.
Howard
