HI,

1994 XJS V12 conv 2+2 won't start on 1st try, starts only after turning key to ACC position first and then retrying. I was told a gas vacuum may cause this. If so, how do I fix this issue.
Thanks again.

 

This happens every time, or only after driving and trying to restart? If after driving, it may be a vapor lock, which would mean you probably have an issue with your charcoal canist/vapor recovery system.

If it happens when cold, can you hear the pump come on and prime when you turn the key before starting? Sounds like perhaps you aren't getting enough fuel and then after a cranking sequence it has enough.

 

Hi,

This happens every time so I think it is a vapor lock. Is there a write up on how to fix this?
Thanks.

 

If the later cars are like the pre facelifts, the ECU switches the fuel pump on for 2 seconds once the ignition is on, but does not keep it running after that unless the engine is cranking/running. This may not be a sufficiently long time to pressurise the fuel rail in your case, for a number or possible reasons. Try the following:

• switch on ignition (do not start)
• repeat
• repeat
• Then try to start.

If the car starts right off, then fuel rail pressurisation is the problem. The easiest fix is to just do as above always!
Greg

 

As Greg said,

AND

At 24 years old, she deserves a NEW fuel pump, and NEW fuel filter.

Neither item last much longer than 10ish years usually.

 

Just out of curiosity, what time of the day are you trying your first start? I know all of us in the midwest and atlantic coast states have been feeling the heat, but my only experience with vapor lock ('87 V12) have been when it's been run for awhile and then parked for a short period of time. Fixing the fuel rail temperature switch cured those issues, I've not had it happen since. And I've never had it happen on a first start attempt, regardless of the temperature or time of day. Then again, mine is a pre-facelift, so many things may have changed between the model years.

Thanks,

John
1987 XJ-S V12

 

HI,

It happens all the time. I think it's time for new pump and new lines.
As always, thanks.

 

My car does this exact thing, if I crank it for a split second like barely enough to have the starter move then try again it'll flick on like a lightswitch. I would also note that often you can crank away and the engine won't fire up but if you turn the key back while cranking it'll come on as if the car is simply waiting for you to stop using the starter before the engine comes alive. The entire fuel-ignition system is new.

No effect on performance or reliability so I assume it just part of the car's 'personality'

 

Maybe I should keep it the way it is then and save the money for something else... Uhmm ...

Thanks for sharing.

 

 

I haven't heard of a fuel rail temperature switch before; is it fitted to all iterations of the V12 (mine's a Marelli) and if so which bit is it?
Part number would be useful!

 

I guess it's no 19 here. I don't have it on my Euro-spec '89 Lucas-HE
Could also be 13, which is a thermal valve controlling vacuum to the LH FPR

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