I am currently repairing an 82 xjs HE with a couple friends. The fuel injectors are being forced open, and we think it is because of a faulty Fuel Control Unit. The injectors are being held open, even though they work fine, and flooding the engine. This flooding hydrolocks the engine. The question we have is, is the FCU the problem? Or is there another thing that can cause this? And if it is the FCU, then is it repairable? I haven't been able to find a replacement with a matching part number.

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First check the harness to the injectors. They're often in terrible shape with missing insulation. If the bare wires touch ground the injectors will stay open.

It happens

Cheers
DD

 

For ECU repair....

aj6 engineering | For the Jaguar enthusiast

Cheers
DD

 

The best thing, having done Doug's very important point about renewing the injector harness, is to replace the 6 CU ECU you have with the later 16 CU. This is a direct replacement, just plug it in. The 16CU is a fully digital unit, whereas the 6CU is partly analogue, and the 16 CU is a far more reliable unit.

 

Yes, get the 16 CU ECU. I had issues with my 85 where it would run fine, then just quit, or run very erratically. Finally changed the 6 CU for the 16 CU. Instant cure.

6 CU's are known for cold or broken solder joints. I opened mine up and resoldered everything suspicious. It then worked, but I never trusted it.

I believe there are two types of 16 CU ECUs, one for Lucas ignition, and the other for Marelli. You have Lucas, so be sure to get that type. It is plug and play.

 

There are also variants with O2 sensor feedback and those without.