I'm still struggling with this issue, so I thought it wouldn't hurt to check here. My 98 xjr will not start after the engine has cooled down for at least 7-8 hours. It cranks, but will not fire. Sometimes, if I'm lucky, it will start on the 3rd or 4th crank. Once started, it runs perfectly, and will start on the turn of the key for the rest of the day (until it has sat for another 7-8 hours). Now, it won't start at all.

I don't think it's spark it runs great once fired. I heard the following suggestions: fuel pump check valve.......and coolant temp sensor. My guess is that a bad check valve would require a new fuel pump. That will be my last resort. I was encouraged about the coolant temp sensor idea; however, my OBD II said that the coolant temp was 18 degrees Celc, which is consistent with the temp in my garage. So even though I've already ordered this part, I'm no longer encouraged that it will solve it.

Finally, there is no fuel leaking externally anywhere in the fuel rails or lines.

Any ideas?
Thanks.

 

Just from my general knowledge of Injected fuel systems..If the Fuel doesn't stay at the point of the injectors and leaks back to the tank, it will take a little time for the fuel pump to bring the fuel back to the injectors..this is known as losing prime..so, next time, turn the key just to the last point, theON position, let it set there for about 30 seconds, then turn the key to crank...If th car fires right up, then it is the fuel check valve or afuel pressure regulator on the fuel rails.

 

Run your fuel system diagnostics first; but if you draw a blank on those, then you might consider the Nikasil issues.Logic: Whenworncylinders are hot, the parts expandthereby providing acceptable compression; but when they are cold they contract and allow combustion gases to escape into the crankcase.

To check for this condition, pull the plugs and perform a compression test. If the compression is low in one or more cylinders;then add a teaspoon of oil to those cylinders to temporarily seal the leaks. If it starts up... Then... Well let's hope its something else first. gordo

 

Or, throw a fuel pressure gauge on the system to see if the fuel pressure bleeds down over an extended period.

 

I tried the priming thing....leaving the key "on" prior to start - no-go. I replaced the coolant temp sensor, cleaned the MAF no-go. I think (hope!) the Nikasil/compression theory is wrong. This is actually my second engine in this car - I bought a used one (80k miles) the tensioners had already been swapped and the compression was great in my "new" engine (when tested 2 months ago) also, when runnning, it is steady as can be at idle (unlike my last engine, which had compression issues). I think compression is fine.

I don't have the equipment to fully diagnose my fuel system.....so off it goes again to the garage. I've spent more money on this piece of **** jaguar than I have on the last 5 cars I've owned (combined). At least my trusty series III can still get me to work.

Thanks for the tips.

 

not sure if this will be relevent to your car, but if it helps,i had a similar problem on a car many years ago.your problem sounds something like what used to happen to my car but the other way round, start from cold, no problem. get it warmed up and your car wont start. let it sit for a few hours and it'll start on the first crank. in my case it turned out to be the fuel pump. apperently it was getting too hot. i also went through expensive route of trial and error and eventually discovered the problem to be with the fuel pump.

T

***still withthe elite, 'cos i still gotthe XK8***

 

try spraying a little fuel mist down the throttle body on the first cold start try of the day. If it fires up easier, then you know it's fuel related. Narrow down what it's not so you can focus on what it is. If it cranks easier, then get a cheap low tech gauge to check the fuel pressure on the rail. Do you have a repair manual yet?

 

Now that everyone sorta leans on fuel problems..Maybe check the fuel filter..Heck, it maybe something simple as that being plugged up.