1981 XJ12 Early distributor diagnosis

(Aristides Balanos) #21


As Mike said, what you reed is 0.7 - 0.3 and 1 Ohms, and I also think they are a bit off…
0.3 Ohm is almost a dead short circuit…


(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #22

We’ll know better when you get a replacement pickup in hand and measure the ohms on it with the same VOM. And, of course, when you swap it out and see if the problems go away.

(Bard Th Hesvik) #23

Thank you for pitching in, guys! I will get out another ‘VOM’ which I think has readings for the lower resistances too, and re-measure it.

If I were to suggest that it all is put together again as it was, and start diagnosing from there, what would you suspect when the engine stalls above idle speed?

Would the engine run at all if the amplifier had failed? Might it be the ballast resistor? I have suggested that he checks for ‘false air’ by spraying ether gas (start spray) at each injector and note any reaction in the idle… plugs and leads have already been replaced. The coil may be another culprit…?


(Ed Sowell) #24

It could be fueling, e.g., clogged filter or intake in the sump tank. Or, it could be an EFI problem, e.g., faulty or improperly adjusted throttle switch, or (unlikely) a ECU problem.

This will be just a guessing game until it is reassembled and some common diagnostic procedures are carried. First, you have to determine if it’s a fueling issue or ignition issue.

(Bard Th Hesvik) #25

Ok, I found another Ohm-meter;

Black yellow: 0,8 Ohm
Black red: 0,4-0,5 Ohm
Yellow red: 1,1 Ohm


(Aristides Balanos) #26

0.4 Ohms is too low, I would regard it as a short circuit.
How many Ohms does your meter show when you connect the two probes together?
Mine shows 0.5 Ohms! Not a very fancy meter though.

(Bard Th Hesvik) #27

Has anybody heard about a Bosch based replacement ignition system for the Jaguar V12?

Some dude wants to install this in my client’s XJ12…