Hi- The car is a 92 Jaguar XJS V12 5.3 with Marelli ignition, and the 26CU 6.0 style intake manifolds and o-ring style injectors. I recently “did the vee” and it hasn’t run since.

The fuel pressure is a solid 40 psi with the injectors firing. The injectors were cleaned by JaguarFuelInjectorService.com, and recently verified by same as working perfectly. I even pulled one out just to watch it squirt (dangerous but I’m desperate)

The spark plugs are firing. A coil strength detector shows they are putting out 15000 to 20000 volts (these tester things are pretty vague cheap tools). Additionally, though these cars cannot be timed, the distributor can be put in wrong. In my case, the lower side of the double decker rotor points straight forward when A1 is at TDC. Aka, it’s in right.

Compression is strong in every cylinder, and the compression stroke is timed correctly with the distributor on A1.

The temp transmitter measured correctly... which in my cold barn was 4.16kohms at the sensor, and 4.17kohms at the ECU connector.

The flywheel and crank sensors have been replaced, just because it’s a common problem. Also replaced coils for the hell of it, cap, rotor, fancy Magnecor wires, correctly gapped NKG plugs replaced twice in case I got antisieze where it shouldn’t be, new TPS, but NOT the ignition modules sitting on the radiator panel because I figured all they do is ground the coil, and if the ignition is firing, then they’re good.

The vac line from the crossover pipe to the ECU held a manually applied vacuum all night, so it’s intact.

There are NO FF codes. I installed the TPS in backwards and got a FF17, but turned it around and the code went away. Disconnecting various sensors does cause thrown codes.

The car does have occasional signs of slight firing.

The car does stumble a bit better with starting fluid, but doesn’t start.

It’s almost like it’s incredibly lean.

So... thats everything! Why won’t this car start? I used to think I was a Jaguar XJS expert

-John

 

I'm aware this is a shot in the dark, but I had a bad no start on my 92 XJS I just couldn't shake and the culprit ended up being the generic switch on the shifter that indicates the car is in park. Its at the front of the shifter below the center console. There should be one for the cruise control and one that signals the shifter position for both the starter and the convertible top if you have one. Cheap part and easily checked.

 

Another 'Shot in the dark' from me

But when I replaced all the Plugs etc

All the Injectors were squirting and the plugs were Sparking but 'No Start'

I was going Crazy! I couldn't figure out what I'd done wrong but after trying everything, I suddenly realized that I had the wires

From the Top Coil connected to where the Bottom Coil should have been connected and vice versa (ie to the wrong Bank of cylinders)

As soon as I changed those wires around She Started on the button and ran perfect!

Might be worth double checking?

It worked for me

 

After OB's great suggestion, if that for some reason does not do it, test for an actual spark at the plugs at the right time (ie about 18 degrees before TDC on the compression stroke).

 

 

Good enough, I would say. Just pull that plug and check there actually is a spark at the plug though. Also, have you removed a plug and looked to see if it is damp? If the injectors are firing, then if the engine is not running, the plug will have petrol on them.