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04 xj8 starts and dies

6.8K views 18 replies 6 participants last post by  2woody  
#1 ·
I was driving down the highway and going to pass a truck when my car just suddenly died on me. All of the dash lights and everything electrical are working fine. Pulled it over to the side of the road and tried to start it bit all it will do is start, idle up to about 1000rpm, and then die.
I suspected the fuel pump so I changed the filter and got a gauge on it. Reading about 28 to 30 with key on and 40 or so at crank up. Leave it sitting and the pressure drops down eventually, but not sure if that's relevant.
It's at my friends house in Chattanooga right now, 5 hours away, but I will be going back up in a couple of weeks and would like to have some ideas on where to start or what to eliminate.
I had just filled up the tank with fuel about 10 min earlier. But not sure what kind of bad gas would have such an effect. Any help would be greatly appreciated
 
#2 ·
Try starting it with MAF sensor disconnected - will eliminate and its free.

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#4 ·
I'm surprised that this is the ONLY suggestion I have received from this question. Surely there is someone else out there that can offer me alternative solutions...Damn y'all, I'm gonna be traveling 5 hours in just a few days to go try to get this car home...
 
#5 ·
#8 ·
I do not think it can be that as the car cut out whilst driving and if it was associated it would not occur until you recycled the ignition.

Roger
 
#9 ·
Another thought is that it could be the CKP (Crankshaft Position Sensors) or the H02 Oxygen sensors as you state you have misfiring.
What were the codes being thrown. It would help if we knew.

Roger
 
#10 ·
Well after I had it towed to my friends house I put a code reader on it but I didn't write them down. I do remember the pertinent ones were the misfire codes. Also, as far as the ckp or the oxygen sensors, I m not sure those two things would cause it to stall out going down the interstate at 70 mph...
 
#11 ·
There is another possibility that of the Alternator. If the alternator is not charging then the engine could start and then just die.

Roger
 
#12 ·
I thought of that, but wouldn't the battery have run down to some degree causing the starter to drag or the lights to dim? It's turning over strong and the lights are bright. Also, if the alternator had suddenly went bad, surely the car would not just die going down the interstate would it?
 
#13 ·
If the voltage required by the functions of the car is below parameters then the vehicle could shut down irrespective of the condition of the battery. The ECU reads alternator output not battery condition. I know its a long shot but something to think on.

Roger
 
#16 ·
+1 for that diagnosis. Otherwise it's an amazing coincidence.
 
#18 ·
You're welcome my friend - glad to have helped. Often the simplest solution is the right solution - many people start looking too deeply!

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#19 ·
it does sound like a fuelling issue - was it raining by chance ?

the fuel pump doesn't work flat out all of the time - there is a control module which decides how hard to drive the pump(s), based on output from the fuel pressure sensor in the fuel rail. It just detects the pressure and when it falls below certain levels, it drives the pump(s) a bit harder. I say pump(s) because XJR has two and a separate box to drive the second one.

It sounds like you have a code-reader available, why don't you try repeating your tests based on what I've told you above.

My XJR suffered from a corrupted wiring harness around the back of the rear subframe, which had become chafed internally as a result of the rear subframe having been removed and mis-handled. the loom goes to the tank aperture and the around the axle before going to the second tank aperture. worse when it rained.

and there's also the scope of the different tank venting system you have stateside, of which I don't know the specifics. Other than its not really an option to run without the filler cap on