So I parked our baby in the heated garage to fix a bunch of things she needed. Removed left headlight assembly to repair a broken bracket, Changed module under driver's non operable seat. Repaired clock and replaced lights in dash and radio. Installed new brakes all around. and replaced an outer tie rod end. Went to fire her up and she cranks but no start. WTF! So I spent 3 hours retracing my steps and plugged in the code reader. Threw a few codes regarding the O2 sensor but thats it. Opened the joint at the fuel rail and gave her a crank. Fuel sprayed out just fine. Swapped the horn relay with the relay on the opposite fuse box. Ignition I think. No go. Reading the forums I see that I should get a reading on the tach as engine spins. Nothing. Bad crank sensor? Didn't show up on code reader. Any thoughts?

 

I just went through this a week or so ago. I had same scenario about 2 years / 3,000 miles ago. I thought, "really? the CKPS is out again?".

So yea, engine cranks but no needle movement on tach. Picked up a new CKPS, 15 mins later after replacing it, engine fired right up.

 

....you know in 15 years of oodles of XJ40's, X300's, X308's and X400's ownership I've never once had a faulty crankshaft sensor....but reading the amount of issues these give X300's I think I'll be getting a spare

CPS failure on Pugs, Fords and Mercs have ALL given me problems breaking down when hot, as in when stuck in traffic and heat soak.
I had a Pug 206GTi that would die intermitantly almost at the same waypoint after a 40 minute drive, that took some finding as it didn't throw a code and would start up again after a 10 minute rest!

...these Jag CPS's appear to die when cooling down from a previous run and that's pretty much it, bizarre, but maybe that the best way to fail!?!

 

And, no, you will not usually get any code for CKPS failure.

 

I'll just add a caveat to the above.

XJ40 and the XJ300 especially don't like being engine bay jet-washed when doing a full vehicle valet and can disable a car for hours, until 'something' dries out with seemlingly no amount of WD-40 helping. Will then restart and drive all OK..... I know from bitter experience!

...I'm wondering if the CPS is at fault and doesn't like being wetted...maybe something going on there?

 

I wash the engine bay every 3-4
months and never had an issue.

My recent CKPS outage, it hadn't rained in days and humidity was low. And when it does rain, it's rare in rains in the garage

This last CKPS outage occurred at the same a number of other unrelated outages: had to replace the BPU and the central locking system and rear trunk (boot) electrical release does not work.

The sequence of outage was: turn key, lights on dash but no crank condition. Replaced the BPU; now a crank, but no start (and no tach needle movement) condition. Replaced the CKPS and she now starts.

Next step, figure out the central locking issue.

 

Well, as usual, you guys are right on. New crank sensor and she fired right up. Happy days. Thanks so much guys. I don't believe I could keep this car without this forum.

 

Having that same problem in my 96 300.. Started off with the car running hot due to cooling fan fuse blowing. Car went into a limp mode it seemed. Trans light came on so I had the bright idea that if I cleared the code(s) for the trans it would come out of limp mode. Car crank and turned over just had no power. Well after clearing codes the the car refused to start. Cranks but won't start. Has been sitting ever since (8 months).. I also have a 95 that I took the CKPS off of to see if that would work but no luck. Placed it back on my 95 and it cranks and runs well.. ANY suggestions would be appreciated.. Thnx