Hey Everyone,

I am new to the Jaguar world - well other than an XJS I had around 25 years back and am having a few issues that I am hoping someone might be able to help out with.

I recently purchased a Series III XJ6 that was a non runner. I managed to get it running and found out it was leaking oils from every orifice imaginable. I decided to buy gaskets and seals along with some other parts and removed the engine to replace everything. Fast Forward...

Everything swapped and put the engine back in. There is a current through the fuel pump wire. As soon as I connect the fuel pump up to that wire, the current stops and the fuel pump doesn't work. If I connect the fuel pump directly to a 12v source the fuel pump works. If I connect the fuel pump to a 12v source and connect it up to the car, the engine starts.

I was wondering if anyone has any input on this as to what it could be?

Thanks, Sam

 

Try cleaning up all the ground connections related to the pump circuit. Corroded grounds are a real gremlin in these cars and an iffy one (or two) can create some weird conditions.
You could also try unplugging the connector from the fuel pump relay and jumping from the battery directly to the WG wire in the connector. If the pump runs normally, the wire to the pump and the pump ground are ok. If that works, touch a test light or DVOM to the W wire in the connector and see if you have 12v with the key on. If there is nothing on the W wire with key on, check the inertia switch at far right of dash. Small black box with button on top, push the button down or see that it's in the down position.
Regardless of the results of these few tests, refer to my first sentence for the best chance of enjoyable ownership.

Dave

 

check the Inertia Fuel Cutoff Switch black box located below the right side of the dash corner mounted to the upper kick panel.

if the fuel system was opened without de-pressurizing it, it may have "tripped" the IFCS.

to check it, push the Reset Button on top of the black box.. If it "clicks", it was tripped disabling the fuel system. If it feels "springy" without clicking, then it is fine.

 

Don't forget the little contacts in the MAF. These close on engine start to keep volts supplied to the fuel pump relay. They are bypassed when cranking.

 

Check out the awesome debug checlists here.

XJ FAQ

 

Thank you everyone,

So I connected the white/green wire up on the fuel pump relay and the pump is working perfectly fine. It was running fine before removing the engine out too. If I connect the fuel pump up directly and leave the car running, I will get a huge puddle of fuel inside the throttle body.

I am going to go through the checklist here but something seems quite off to me. I am normally a Mercedes guy and have never experienced something like this on them but it is really fun working on this beauty.

Sam

 

That's pretty weird. I can't see how fuel can end up in the throttle body at all.

Do you have all the various hoses hooked up correctly? That's what pops into my brain at the moment....although I'm tired and bleary eyed.

Cheers
DD

 

Sorry, I should have been more clear, it is in the intake manifold just behind the throttle body.. And a pile of it. Something is definitely a miss. Fuel is getting through no problem and car starts fine if I wire up a pump directly to run full time but there is a backfire if I do that as all the excess fuel in the intake manifold pops.

 

A leaky diaphragm in the fuel pressure regulator could allow raw fuel to be drawn into the intake. Badly leaking or stuck open injectors could cause pooling of gas. The cold start injector is a good place to look.

In any of those cases I'd expect the engine to run very poorly due to over-fueling.

I'll do more thinking

Cheers
DD

 

I just wanted to thank everyone for the replies, I have done more tests and it seems the injectors are not working. On a tester there is current in the wires but when I connect up a lamp via wires to the injector, I get no on / off pulses on the lamp and listening to the injectors through a long screwdriver shows there is no noise coming through them. Obviously electrical now but any hints / thoughts?

 

Here's an easy one to check:

At the rear of the water rail there is (or should be!) a bundle of 5-6 ground wires. These are the grounds for the entire fuel injection system. Make sure the ground contact is clean and tight....and that none of the wires are dangling in air !

Post back if no joy.

Cheers
DD

 

Thanks so much Doug, will get on this first thing in the morning