Hi everyone
my name is Billy and I have just joined this forum and sorry my first post is a problem. I have a 1995 jaguar xjs 4.0 auto aj16
was running fine and suddenly cut out and I assumed fuel has gone so put fuel in and cranked but no start, just cranks, heavy smell of fuel and I can see cold fuel leaking out of exhaust front pipe and even from back box joint. I removed injectors from inlet and just turned ignition on and it was pouring Petrol out through all injectors just with ignition on at fast flow for like 30-40 seconds constant. I am baffled to say the least as car was fine the other day
how can all injectors be pouring so much fuel out just with ignition
Ecu maybe ?
your help and advise would be much appreciated

 

This is a short video to give you an idea of the speed of the fuel coming from injectors just with the ignition on

 

Video

 

I’m assuming you typed diesel back there by accident?

None of your links to any videos work.

 

Yes my mistake have corrected it now

 

I have tried to attach it again, hopefully you can see now,

 

That’s pretty ridiculous!

Generally speaking, injectors fire with ground switching. The hot side is always hot, and the ECU just grounds the injector it wants to fire at any given moment. You should review a wiring diagram to verify if I’m right.

So if a ground makes the injectors fire, either you have introduced a permanent ground somewhere between the injectors and the ECU, or your ECU is grounding all the injectors simultaneously. A worn wire could ground itself… but grounding all six sounds unusual.

Good luck! Study that wiring diagram!

-John

 

What is your fuel pressure? There is pressure regulator on the return line, to best of my knowledge on your year car. Too much pressure = too much fuel.

I can't watch your vid due to my very slow internet satellite connection. I really should sign up for Starlink.

Doug

 

You for sure have a short to earth (ground) on the injector circuit. It could be the injector loom, or a fault in the loom to the ECU from the injector loom, or a fault in the ECU. Start by carefully inspecting the injector loom.

 

I'd start with AZDoug's recommendation. Check the fuel regulator. If you pull that little rubber vacuum hose it should be dry with no scent of fuel. If it's wet, it is shot and sending the full force of the fuel pump to the injectors which could be bad? That's a quick and easy test.

Next, pull the harness off of your ECU, see if there is any visible corrosion on the pins.

After that, I would look at the ECM Controlled Relay. I think it's as simple as swapping it with a known relay, which you have plenty of.

On second hand, it might be cheaper to do this in reverse order. The regulator is not a commonly known failure point.

 

Thank you everyone for your help and advice. Today I pulled that rubber hose off and it was dry not wet, I put a test bulb on injector (node light) and put ignition on and it the bulb stayed on constant and didn’t blink. So I tested for an earth when the Ecu is unplugged and no earth. Would this suggest I don’t have a ground problem and is Most likely the Ecu itself ?

 

Work in order. Sounds like you have crossed fuel regulator off the list. Good.

If you suspect an ECU problem, pull the connectors off and look for corrosion, which is quite common.

After that, swap relays with the ECM controlled relay.

There's also an EMS Power Relay that seems to provide grounds to the coils which could be swapped out.

Let us know what you find out.

 

Can I ask where is the relays located please
I see one near the ecu and it’s a pink colour relay?

 

Both relays (light blue) are where the glove compartment would be in a normal car. It's below the passengers side airbag. You'll have to pull down the panel and there they are.

You might want to go to JagRepair.com - Jaguar Repair Information Resource and download electrical diagrams for your car.

You should also order a service manual. You have many relays, you're going to want to know where they are and what they do.

Please don't forget to pull the connectors from the main ECU. As I've mentioned before, corrosion at the pins is a common issue on these cars, easily resolved with some contact cleaner.