I am having a persistent hot start issue for the last few weeks.
When cold the car fires up as normal and idles fine.
When hot, i.e. driven for 45 minutes to an hour at normal temp:
If I shut down the engine and immediately try to restart - it fires up straight away.
If I shit down the engine and wait to ten/15 minutes - it needs to be cranked a couple of times before it will start on the third attempt.
If I shut down the engine and wait for an hour - it needs one crank and will always start on the second attempt.
It is very consistent. When I say it needs two cranks and will start on the third, it really will. It doesn’t seem to matter what the outside temp is or any other variable.
Another consistent symptom is that the fuel pump does not run for it’s normal 2 seconds when trying to start hot. Only after the cranking is done and the key turned again do you hear the telltale whine from the pump and then the car starts right up.
A lot of posts in the archives would suggest fuel pressure, but wouldn’t I expect the pump to be trying to prime every time if the pressure was dropping? And if there was a leak down or a check valve issue wouldn’t the cold start also be affected?
an old engine starting after three cranks doesn’t sound bad at all to me!
I would guess you’re just dealing with slight vapor/hot gas in the fuel rail.
Oh, just read your other part. Yeah, if the fuel pump is not running for it’s normal 2 seconds when hot, then you don’t have good fuel pressure to help start it. How old is your fuel pump? The fuel pump will prime no matter what the fuel pressure is.
I take it your fuel pump is in the tank? So not easy to replace…
FPR is another place to check, perhaps when it’s hot, it doesn’t keep pressure up high enough to start easily?
Hi everyone, I know one thing that upsets the people that give up their time and expertise to help the rest of us is when we don’t come back with a confirmed resolution to a problem.
So I wanted to let you know that the reason I haven’t done that is that I still haven’t fixed this problem!
I have changed CPS, CTS and FPR. Symptoms are exactly the same as they were a year ago, when the car is hot:
Turn ignition on, no 2 second noise from fuel pump, engine turns over and does not start.
Turn ignition on again, no 2 second noise from fuel pump, engine turns over and does not start.
Turn ignition on for third time, 2 second noise from fuel pump and engine roars to life as normal.
It is always the same, no random variation always three goes and only when the engine is warm.
If you are saying the fuel pump doesn’t run on the first 2 attempts then
this part of the circuit in the ECU must be the problem. When my ECU
failed, I did draw out some of the circuit but not this part. Normally
electronic timing circuits are done by charging a capacitor. When the
capacitor is charged, it need to be discharged before the timing circuit
will work again. If anyone can give me an ECU circuit, I can tell you
where to check. I would guess that this part is the same on all XJS &
XJ6 ECUs.
To be clear your running the AJ MOTOR correct.
If you run the fuel pumps on low tank of fuel, they will HEAT UP and burn out as they suck in junk from the tank. Are you getting hesitation after awhile.
Your back to pumps, crank sensor or ecu, but if its hot issue, back to pump and filters…
Its 26 years old…Change the pump and filter.
good luck
gtjoey1314