!987 Jaguar xj6 4.2

Started By: Sharon Sidoti on 2014-08-22 16:28:15

While trying to figure out why my Jag. starts, then stops and will not start again,I came across this situation...I pulled the spark plugs, they were wet, for some reason I opened the door on the passenger side gas tank, started the car, and fuel started coming out of the tank, I shut it down. After a little investigating I found a valve (in the spare tire well) with three lines connected to it, I removed the valve, connected two lines, the line returning back from the engine I put into a gas can, started the car, it runs great, continually, but, fuel come from the return line, what is going on??????

Comments

Edited on 2014-08-22 23:22:28
That's the 'changeover valve'. On command from the dashboard switch it determines which tank gasoline is drawn from. None of the three hoses on this valve is a return line. It has one supply hose from each tank and the output hose to the fuel pump.

The return line is under the car and branches off ahead of the rear wheels. Each branch has a return valve (located in the wheel well) that open to allow unused fuel to return to the tank it was drawn from. So, for example, if the RH tank is selected the changeover valve opens to allow flow from the RH tank, and the RH return valve opens to allow unused fuel to return to the RH tank. The LH return valve is closed.

However, if fuel is drawn from one tank but returned to the *opposite* tank, the opposite tank can overfill (and actually overflow) and flood into the venting system and eventually into the vapor canister...when it can be drawn into the engine and cause drastic over-fueling. This might be the cause of your wet spark plugs.

Here's info on checking the system

http://www.jag-lovers.org/xjlovers/xjfaq/fuelchangeover.htm

Cheers
DD