Engine starts and runs great until reaches operating temperature. Then shuts down and gives code that not ready. Will not start until cooled down. Then repeats. This happens whether driving or parked at idle. An ideas?

 

1999 XK8

 

Interesting problem. What is the actual code you are getting. The engine temp sensor would peg the dash gauge but I don't think it would actually shut down the engine. Does this occur while driving or while sitting and idling? If while idling have you tried checking with the bonnet open and idling. It may be a heat build up on one of the electronic components. I am thinking ignition amplifiers.

 

Code is P1000. Temp gauge never goes above mid point. Same result if driving or sitting at idle with bonnet up.

 

Check that the cooling fan under the ECU is running.

 

Does it sputter and die? Do you have fuel pressure on the rail (schrader valve under the right side engine cover, take rag and push down on pin to see if any fuel sprays out) after it dies?

The code is just telling you that the drive cycles have not completed (P1000, i.e. the codes have been reset recently), not particularly useful here if you can't drive.

Since these engines are designed to reach operating temperature very quickly (can be 100-200 seconds out of my driveway in the summer), how long does it usually take before it dies?

 

A possibility, and something good to look at, but I've measured the ECU/ECM surface temperature with and without the fan working (since my fan didn't work originally). It takes a fair amount of time to get the ECM anywhere near its design temperature (85 C), from cold, even with the fan off, even in the summer, because the ECM/TCM box communicates with the passenger floor, and is insulated to a degree from the engine, and a there appears to be some passive convection. Some of this is discussed here:

https://www.jaguarforums.com/forum/x...ration-223001/

 

The obvious would be an air leak which occurs suddenly. Most likely there's a crack in a plastic part or split in a hose or a loose hose or ...

 

Like mentioned earlier, how does it die?

• Does it shut off instantly like you turned off the ignition?
• Does it start running roughly and then quit?
• Does it begin misfiring badly before quitting?
• Are there any sounds/smells as it dies?

We need more to work from.

 

Thanks to everyone for your replies. To answer a few of your questions:
If driving it sputters and looses power before quitting.
If Idling it just shuts down like switched off.
No smoke or funny smells.
Time varies on idle shutoff. Never overheats.
Have determined that fuel pressure is low. When starting cold initially had 30 psig. dropped to 15 then dropped to 6 and surprisingly kept running. Actually idled for 10 minutes at 6 psig. After cooling down restarted at 6 to 10 psig. Thought my gauge faulty. Same results with 2 gauges (one new). Pulling pump to check today. Will let you know what I find.

 

What is the history on the fuel filter?

Also, as a sanity check, what happens when you pull (and plug) the vacuum line to the fuel pressure regulator? Pressure should read higher...

Last, check the wiring diagram, and swap like relays in case you somehow have one with high resistance. Also check voltage at the various fuse boxes (including the trunk) in case one of those power cables is loose. Double check the battery cable for heat as they sometimes fail internally and cause a voltage drop.

Hard to be sure, but normally fuel pumps just die.

Best of luck, keep us posted.