Dropped the top the other day to go for a drive in my 1990 XJS and turned the key, lots of spinning over and lots of not starting. Spark, Check. Fuel pressure, Check. sprits a little starting fluid and she tries to start. So injectors are not doing their job. It is in the shop now after a nice drive on the rollback. Mechanic is researching the possible issues. He says the relays are ok and he is now trying to figure out how to test the various components that are involved. He is a great European mechanic but Jags are a little outside of his wheelhouse.


Any ideas on what part that is common to go **** up on these cars to cause this? The car was driving fine a week or so before I parked it. I figure it is something simple. I hope!


DJ

 

V12 or AJ16?

 

Assuming a V12....and assuming he has at least checked for voltage at the injectors......

Have your guy check the crankshaft sensors. Fairly common for them to fail. There a two: one at the crank pulley (TDC sensor) and one at the flywheel (engine speed signal).

The fuel injection ECU is 'triggered" by input from the ignition ECU.....which in turn takes the trigger signal from the rear crankshaft sensor or engine speed sensor. No engine speed trigger = the ECU staying asleep.

Lots of other possibilities such as injector harness fault (common), a injector ballast fault (not so common)....and others that I can't think of at the moment.

Cheers
DD

 

V12. I spoke to him a bit ago and he said there is no voltage at any of the injectors.


Thanks Doug

 

Might be worth trying this. What you described happened to me a week or two ago. This was the trouble:

https://www.jaguarforums.com/forum/x...sistor-134745/

Greg

 

if you don't have voltage at the injectors then you have a different issue to normal

as the injectors are ALWAYS LIVE , and the power resistor fires them through the ground wire through the ECU

the injectors get there power from the ' main relay ' in the boot/trunk ,

this is mounted by the battery and the fuel pump relay ,

the main relay should , if still original , have a diagonal red stripe on the top to indicate its importance

if this relay has failed then you will not get power to the injectors ,

you need a special relay with two pins ( 87 ) on the output, as the second pin provides power to the fuel pump relay , this relay is switched by the main EFI switching relay from the ignition


BB

 

Thanks for the help Doug. It was the front Crankshaft position sensor. Time to get back in the wind!