Let me tell you what happened and what I have done to try to fix it.
My car is a 1995 XJ6 3.2 litre with an auto box. It's a gorgeous car but it was bought cheap, under £1,000, and taking it to the shop and saying, "Here's a cheque. Fix my car" is not in my budget so I need to try all the fixes that I / you can think of first.
Under normal circumstances, I get in the car, fire her up and drive away. No problem whatsoever and she is a joy to drive. That's what makes it so maddening when, having driven the 30 miles to where you want to get to in a calm, relaxed manner while waving to the peasants in lesser cars, she won't start when it comes time to drive back home.
The key fob unlocks the doors and the alarm is turned off at the same time. Giving the key a half turn in the ignition brings up all the lights, some of which go out shortly after lighting. Another turn of the key and the starter motor turns over the engine very powerfully with none of the kind of dragging noises that you get with a battery on its death bed.
She will crank over for 20 seconds or so with not really any drop in power. Even a second attempt still shows a battery with lots of juice so I don't think it is a battery problem.
I have taken off the ski slope woodwork and adjusted the little spring that recognises that the gear selector is in the correct spot and that now works fine.
Like I said, she's a joy to drive but the problem is that she can't be trusted. I can't get my wife and grandkids in the car to go to the beach for the day because I can't be sure that we won't need a breakdown truck to get us home.
OK, I'm not a mechanic but I can follow instructions so if this all sounds familiar to anybody, please feel free to give me a holler.
Cheers,
Steve

 

Crank position sensor? You need to watch your RPM needle next time it happens. It should register about 200rpm. If CPS is the problem, you won't get the RPM needle moving.
The CPS is probably the number one culprit in non start (but cranking) x300. I think coolant temp sensor may be high up on the list of non start culprits too.
If you can get acccess to a diagnostic tool it might point the way.

 

Hi Straight Guy. It's been a while, huh?
So let me see if I got that straight.
If I turn the key in the ignition to crank the motor over and it is the fault of the CPS that the engine fails to start, then the rev counter will stay on zero. On the other hand, if the engine fails to start but the rev counter is showing about 200 revs during the starter operation, then the CPS is NOT the problem.
If I read your post correctly, that is exactly the sort of reply that I was hoping for. Simple tests that I can do myself that "may" fix the problem but that will certainly allow me to build a list of things that I have checked so that if I finally have to admit defeat and take it to a garage, at least I can tell the guy what the problem isn't.
Thank you.
Steve.

ps ... I'll try it next time she fails to start and post what happened re the revs.