98 XJR - I just replaced my engine with a used 98 XJR engine (tensioners have been replaced) it runs great now; however, it doesn't want to start from cold start. It will just keep turning over and not fire. It will usually start on the 4th or 5th try if I'm lucky - once it's been fired up, it will start for the rest of the day on the first turn of the key - only has problems with the first start of the day.
I have no idea why this is....... any suggestions???

 

Skanoski, as I am still learning about Jags, this will be a shoot from the hip kind of diagnosis. It sounds to me like the problem is fuel and not fire. The problem may be the fuel rail loosing it's prime so to speak from a leaky fuel pump check valve. This would allow the fuel to flow back down from the engine over several hours. I would think if it was leaky injectors it would at least try to start on the first try.

Joe
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[align=left]To test this theory, start the car and let it run for only about a minute right before you go to bed. Then see if it starts easier first thing in the morning.[/align]

 

not sure what the deal is - the threshold from the engine firing right up to barely starting is around 8-10 hours of cooling off. Any other ideas?? How would I diagnose a leaky check valve?
thanks ...

 

[align=left]I think we have enough information to make a good diagnosis. The good news is it may be a cheap or easy fix! Start thinking in terms of, "it takes 8 to 10 hours of the car sitting, for gravity to pull enough gas out of the fuel rail to cause it to barely start.

Did this starting issue appear right after the engine swap? Is the car sitting in a garage? Is there an odor of gas around the car now, where there was not one before the engine swap?

If the answer is yes, you may have a fuel line fitting seeping gas. I would start at the fuel rail, check for leaking line fittings, leaking injector fittings etc. Rub your finger under them then smell your finger. Then work your way back, check the fuel filter area and any other splices or fittings in the fuel lines.
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fuel pressure gauge.. or pinch the return.. does it fill like its flooded?

 

I think the problem is in the throttle body. The electric motor that opens the throttle may not be able to overcome the goo trying to hold the throttle plate shut on initial start for the day. You may need to clean the throttle body. The check valve in the fuel pump could be involved, but the pump should pressurize the system much faster than 5 starts even if it was at 0 psi. After all night, the pressure in the system would below even if the check valve was good. You might put a tester on it to check fuel pressure for sure. The check valve will only hold 21 psi for an hour after shutdown, the system gradually goes to 0.

 

thanks for the replies - I'm having a crazy busy week and hadn't checked back on the thread yet. Joe this problem appeared right after the engine swap, and not before. The car is sitting in the garage - there's no smell of gas anywhere, and no obvious leaks at the rail or the injector fittings I plan on checking much closer this weekend when i have more time

I don't have a fuel pressure tester - I may get one this weekend when I dig in a little deeper. Also will check the throttle body tonight - it was clean as rain before the swap, but who knows. I'll let you know how it goes