I have an "86 XJS V12 with fuel injection. It will start with the key in the "start" position but as soon as the key is moved to the "run" position it dies. It can be kept running in the "run" position by spraying Carb Cleaner or Starting Fluid in the Air Intake. Obviously the ignition system is OK, the problem is that something is turning off fuel flow in the "run" position, probably by cutting off power to the fuel pump. What would do this? Someone mentioned a gizmo in the distributor that sends a signal to a computer somewhere. Anyone know anything about this and how to diagnose it?

I'm an old time mechanic but diagnosing electronics is a challenge.

Thanks in advance.

Submitted by dougdwyer1@com… on Tue, 06/22/2010 - 09:10

The "main" relay....which powers the ECU and is the voltage supply for the fuel pump relay, is sometimes called the "start" relay.

And I *think* that the earlier HE engines.....the ones that still used cold start injectors....had a "start" relay just for those injectors.

I'm fairly sure, though, that the 86 in question will have just a single fuel pump relay.

Cheers
DD

Submitted by dougdwyer1@com… on Tue, 06/22/2010 - 00:42

For engine starting the fuel pump circuit is activated by the starter circuit. For engine running the fuel pump is controlled by the ECU in the trunk.

Go to the fuel pump relay and ground the orange wire....which is what the ECU does when everything is working right.

The relay is in the trunk, right hand side, behind a plastic cover....sorta up there by the trunk lid hinge.

Shout back with the results.

Cheers
DD