I know this is a NOT an unusual topic.. But Now I am stuck..

Have fuel..Have fuel pressure..Have new coolant switch(2 wire),
Have spark..Have also substituted ECU from another XJS(same #), Have checked resistor box.......

Engine cranks, but will not run.. Injectors will not pulse..
Ign computer is original, as well as sensors

Problem occurred after a stumbled start, drove home parked in garage now a dead kitty..
Any help would be appreciated

Regards,
Henderson

 

Replace the CKPS on the FRONT of the engine??????

A failed REAR engine SPEED sensor will cause the engine run poorly but a failed FRONT sensor (POSITION) will 'SHUT-IT-DOWN'. (pretty common fault)

The sensors are the same, so if you want to do some labor intensive replacement experiment you could swap sensors and it 'SHOULD' start but run poorly.

I just replace the front sensor and go on with my life.

bob gauff

 

I thought the coolant switch would do the same... Thanks, I think I will buy a new one one just for giggles.
Not much to laugh at at when in the garage !!

Regards
Henderson


PS I will post results one running

 

I've moved your post from the General Tech section to the XJS section for greater visibiity

 

Is the fuel injector wiring harness connected and in decent shape?

When you say coolant "switch" are you talking about the coolant temperature sensor on the LH front water manifold? If you've got a 1K or so resistor (value is not critical) unplug the plug from the coolant temperature switch and short the plug with the resistor. If the temperature sensor is the problem then the car should start.

Thanks,

John
1987 XJ-S V12
64,000 miles

 

Thanks JCR.. I replaced the CTS and ohm valued switch cold and the ECU all ohmed very close to the same # (1.8) Pins # 5 & 19.
I had to re work injection harness in prior months..fix broken wires(heat) car ran very well until a momentary stumble, no power, then regained its last breath and died !!.
I will take harness apart and look for s problem.. because the injectors are not working...
Thanks for your time .. John

 

Had my 1990 xjs do the same thing, Front position crank sensor.

Steve.

 

Thanks Steve, On my list to replace... after all it only 24 years old.!!!!
Once running,I will share the grief of pursuit.

 

If I might throw in my .02 cents worth, I would check the clearance of the "crank sensors" first. I bought a 89 Marelli car (same as yours), that had been worked on by a Jaguar shop for months without success. I bought it not running. It took about 40-50 hours of trial and error, but I finally figured out the problem. The front and rear "sensors" aren't really sensors at all. They are small electromagnetic pulse generaters. They produce about .08 volts AC during cranking, and the rear "sensor" can go to as much as 80 volts AC at wide open throttle. These "sensors" are electromagnets, or magnetos. What I found on my car, is that the rear "sensor" was about .047" away from the flywheel. The front "sensor" triggers from three fingers. It was varied in distance. What I did, was file the mounting boss(es), until I got the rear one to about .020 from the flywheel, and the front one, about the same on the closest(sic) finger, and about .032 on the widest one. The car literally fired right up. What I came away with, is that my car most likely never ran right from new. What I recommend, is that ANYONE with a Marelli car check these clearances. Given the age of the magnet, I would presume that even if the car ran with excessive clearance when new, after the heat, time, and distance of what causes it to produce voltage, take its toll, the car cannot run as intended.
Take a look at airplane engines. They are magneto fired even to this day. Yet, at 2000 hours, the magneto(s) must be replaced, for the very same reason. Can't afford a misfire, or failing ignition at 20000 feet.
Hope this makes sense, contact me if you want, doubt me if I'm wrong.

 

Super Charged :Thanks for your input. I will look at the respective distance of both sensors. Age and heat will warp the plastic.. I do have fire to the plugs, but all systems have to work together.
Thanks again,
Henderson