So after driving around for a while and the engine is nice and hot, I am having trouble restarting the engine when getting back into the car after running into the store etc…

She will restart but then promptly shutoff. I have to pump the gas after I gets running to keep it from turning off. I did make a small adjustment to the Extra Air Valve prior to this happening. Is this the reason for the problem? Any thoughts on how to remedy the issue is greatly appreciated!

Cheers,
Scott

1992 XJS V12

 

First thoughts fuel vaporisation - known challenge with V12 under bonnet temps - your AC in good condition ?? - why did you adjust the AAV ? - presuming some issue with idle speed (because thats all you can adjust with it)

 

AC is not working at all. Haven’t gotten around to fixing that issue…

Yes you are correct I was adjusting the idle speed earlier in the year.

- Scott

 

Idle Speed - Adjusting up or down ? ...

How much fuel you keep in the tank may impact this behaviour - the XJS uses the AC to keep the fuel cool, the hotter the fuel in the tank gets the more prone it will be to do this, add this to high ambient temperatures and the V12 will vapor lock in a hearbeat.

You need to be sure of the culprit behind you modifying the idle - you sure the throttle butterflies are correctly adjusted, linkage correctly adjusted and no intake airleaks (my manifolds were loose).

I think a simple test of vapor locking is to drive the car in a manner that produces this not starting scenario, when you stop open the hood and wait as long as you would were you following the normal pattern, then try to start the car, if it fires up straight away and stays running it is vapor locking.

Somebody posted a trick to get the pump to flush the injector rail but I'm struggling to find it - it could be as simple as turn on the igniton but don't immediately try to start - leave the pump run to refill the rail - I think ...

 

Awesome thanks for the help! I’ll give it try and hopefully will be able to run it down.

As for the idle, I was adjusting it down. It was running a little high.

Cheers,

Scott

 

I believe you 92 has a non return valve in the fuel system (after the pump). Their function is to hold pressure in the fuel rail when the engine is off. It often fails. Try replacing it.

 

ok great I’ll give that a try as well. Thanks for the help!

 

Hi Scott

On the Side of the Fuel Rail on my 89 + 90 XJS's (see photo) is a Wax Thermostat 'Thingy' designed to assist with easier Starting during very hot Weather to overcome Fuel Starvation after the Car has got hot and has been switched off

As you can see there are 2 Vacuum Hoses going into this where the Vacuum passes through this Wax Thermostat 'Thingy' and if the Wax inside this melts as it did on mine it can shut off the Vacuum

Less Vac = More Fuel

More Vac = Less Fuel

So when this Wax Gizmo melted on mine, then it just cut off the Vacuum, so that my Car was 'Over Fueling' as it may be doing so on yours, so since it is debatable as to whether or not this is ever needed, I cut this Vacuum Switch out of the mix, with a Single continuous piece of rubber tube and the problem was solved

And I've never had a problem with any Hot Re-Starting Since and so it might be worth a try



Wax Thermostat 'Thingy' causes Major Problem and so I by passed it with a Single Piece of Tube

 

Hot start issues suck…. Relays are rarely seen as a problem so check those out too