When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I was pulling the beast out of the garage this morning to drive to a local Cars & Coffee event, and it suddenly died on the driveway and wouldn't restart.
Car has been running beautifully and I drove it yesterday to put some gas in it so I wouldn't have to do it this morning. I only put 4 to 5 gallons in at time so I'm keeping the fuel fresh. No sign of any trouble or issues on the way home from the gas station.
Fired up immediately, and didn't stumble or anything, it just died. Cranks with no issues, but doesn't even pretend to be firing or catching. Looking at the Wizard's No Start pdf, but mine is a Marelli system so I'm not sure where to start.
The only other thing I did yesterday was a smoke test to see if I had any vacuum leaks and I used the hose going into the fuel pressure regulators to do the test. But that was before I drove to the gas station so if I disturbed something it still ran fine.
I don't think it is a fuel issue. Had the wife turn the key on and could hear the fuel pump prime for 2 seconds. I can hear the injectors click when I turn the capstan. Tried spraying starter fluid into the throttle body while the wife cranked the starter -- nada.
Tried the Wizard's CTS plug paper clip trick, still no joy.
BTW, should I be concerned about repeated attempts to start if it is indeed getting fuel? Any fear of hydraulic lock?
Agree, based on the little I know of Marelli, its lost spark and Injector pulse.
With no activity with Ether, is NO spark for sure.
Injector clicking on capstan rotation, or lack of, not sue on Marelli, , BUT, they do run the 16CU geezuz box, so I reckon that applies.
Check and clean the Resistor pack plug and socket, getting old and grubby after 35 years.
I can't find any record that I had previously replaced the crankshaft sensor or the flywheel sensor so I must assume they are original. I don't like to "throw parts" at a problem generally, but after 35 years it seems prudent to replace both regardless.
I checked https://parts.jaguarlandroverclassic.com/ and it looks like the OE ones are no longer available, but I sent them an inquiry anyway and will report back when they reply.
Has anyone used an aftermarket one with success? If so, what make and number please. Thanks!
I THINK you might find that you can get the front CPS but not the rear one. However, I understand that the only difference is the angle of the rear one and a front one can be used / adapted. I hope I'm not misleading you!
I THINK you might find that you can get the front CPS but not the rear one. However, I understand that the only difference is the angle of the rear one and a front one can be used / adapted. I hope I'm not misleading you!
Interestingly if I search their site by the three different part numbers I could find -- DAC4606, DBC12507 and DBC12508 -- everyone is illustrated as the flywheel speed sensor not the crankcase one.
From my research so far, on the 5.3L cars the two sensors are interchangeable. On the 6.0L's is where the angles are different.
Last edited by Mac Allan; Aug 4, 2025 at 03:19 PM.
I might not have eliminated the CTS after all. I did the paperclip test on the sensor located on the LH side per @Grant Francis 's won't start .pdf; however, after looking at the Marelli Supplement doc, it appears that the Marelli cars use the RH CTS to send a signal to the ECU.
Is this correct?
The RH CTS is harder to reach and I don't want to go disturbing things to the do the paperclip test if I'm incorrect.
Also, it shows that it uses the Air Temp Switch on the RH air housing, and doesn't reference the ATS on the LH air horn. What does the LH ATS even do if it isn't wired into the ECU?
I've just read through various sections of the Workshop Manual and it's pretty clear that it uses the sensors on the A Bank as per your pic. It. also states that the Primary Inputs which are necessary for starting are the 2 CPS. It says that the CTS is a secondary input and will not prevent the engine from starting. Take that as you will!
Update -- I heard from our friends at Jaguar Land Rover Classic Parts and they no longer make or offer the CPS/Flywheel Sensor. Aftermarket is the only option.
Update -- I heard from our friends at Jaguar Land Rover Classic Parts and they no longer make or offer the CPS/Flywheel Sensor. Aftermarket is the only option.
Make sure you tie a string or flexible wire to the top end of the front CPS you are removing so you can get the new one routed back in. I'm not sure about the rear sensor.
Orangwblossom did a GOOD write up a while back, so search for his posts should give the answers.
It took a long time to find @orangeblossom 's write up, but unfortunately it was a tale of spending hours getting nowhere until his GF took over and got it sorted without any explanation. He said next time he'd pay someone to replace the cps. So unless he has since done another one, how to do this isn't looking promising. Nothing in the MY1990 ROM or the Marelli supplement that I can find.
Well that was surprisingly straightforward and drama free.
The string trick worked a treat, but something interesting cropped up. I assumed that the CPS was original and had never been replaced because I didn't have any record of it. However, it clearly had been replaced at some point because the cable didn't go through the upper P clip. Back when I had an independent Jaguar specialist do the service (he owned an XJS and was the service manager at the dealership when the XJS was a current model), he must have done it as a preventive maintenance thing at one time. He may have figured out an easier routing path for the cable. It was almost easier to do the CPS/TDC than flywheel sensor.
I was tempted to do both before I tried to start it, but decided it would be good to know if the CPS was the cause of the no start condition. Car started easily after the CPS was replaced.
Died backing out and won't restart
