Hi everyone, I have an intermittent problem starting my 2005 XJ8 VP with 78k on it. It only happens after it's been sitting for a while (overnight) and doesn't always happen consistently. When the issue does occur, the engine still cranks fine but almost starts, sometimes to the point where the starter kicks out and you have to cycle the key again to crank further. Sometimes this is a few extra seconds of cranking and sometimes it's multiple tries for 10-20 seconds before it starts. As soon as is does start, it runs perfectly and doesn't cause an issue again until it's at least sat for an extended period of time. The problem was getting fairly consistent and then I took a six hour road trip and had no issues for several days even after it sat for a day. Then the problem slowly started up again. I've tried cycling the key to see if it's low fuel pressure (am I right there's no fuel pressure valve to check on the 05?) and that appears to do nothing. I've run injector cleaner through but also doesn't seem to solve it. I had heard/read/seen somewhere that leaking injectors would be more of an issue on a hot start but don't remember well enough where or how I came to that conclusion to trust it. It seems like if the pump was failing I'd have some issue running wide open but it's smooth and powerful. I've had no codes whatsoever. I do have a BlueDriver code reader and fuel pressure is low 50's when running, drops to immediately to high 40's when car is shut off and right back up to low 50's when started again. I don't believe this is at the rail, not sure where it's getting the reading from but I think my app says at the rail isn't supported on this vehicle. It's been a little while since I checked that. I haven't been overly motivated to find the issue since it's never left me stranded and it's hard to diagnose something intermittent. I'm getting ready to sell this vehicle and wanted to resolve this issue before I did. What should my approach be? I don't mind doing work myself and would rather not sink a ton of money into it right before selling. Thanks!

 

Hi! You’re problem sounds exactly what I’m going through same model as well. But now it stopped working completely. I change fuel pump, inertia kill switch and trunk fuse box and nothing. I’m not getting no fuel pressure. Were you able to solve your issue? If so what did you do?

 

How old is the battery on the car? Jaguar XJ8s are notably finicky if the battery voltage should dip below a certain point (~11.5VDC)) while cranking the engine. I mean, they just won't start no how. Try attaching a voltmeter across the battery, and monitor the voltage while cranking the engine.

You could also try placing a jump on the battery while cranking the engine.

 

I’m not sure how old the battery is. I just bought it about a month ago. It was driving perfectly fine. Then it start having the long crank problems then a week later it just didn’t wanted to start what so ever. It cranks but it just doesn’t star. There was no power going towards the fuel pump, that’s why I replaced the trunk fuse box thinking it was the fuel pump relay because They can’t be replaced by themselves. I had tried to turn it on with a jump the first time it happened to me before replacing and after replacing parts.

 

Check those earth ground connections first, and especially in the trunk area of the car.

 

I had a similar issue - long starts. My problem was the check valve inside the fuel tank that allows the system to retain fuel pressure once the car turns off. The way to find out is to hook up a fuel pressure gauge on the fuel rail and see what the fuel pressure does when you crank, start, stop. If nothing else, you can eliminate the fuel delivery being a problem.

 

All the ground wires look good. I replaced the battery and same thing. I have no fuel pressure but that’s because I’m not getting no power to the fuel pump.

 

I got no fuel pressure on the rail but it’s because the fuel pump isn’t getting any power. I change the trunk fuse box since the fuel pump relay is part of the PCB. And still doing same thing. I already change inertia switch, trunk fuse box, fuel pump and battery.

 

We have two different problems in this thread which points out the problem of piggybacking on another thread. First is a long start. And second is fuel pump not kicking in.
The first will log a flight recorder showing parameters during the start - may help in diagnosis. It may also be logged for the second problems as well. Worth checking in both cases.
The first could be faulty temperature sensor, leaking injector, slow feed from pump to injectors, bad grounds (grounds looking OK does not mean they are - you can not see electricity flow.), etc.
The second could be the fuel pump relay however the ECM controls the pump relay output with a PWM signal that needs to be checked. SDD (and possibly others) will show the ECM output live data.