'97 3.2 Sov, Andy Bracket, K&N pod filter.

I have had this issue happen a couple of times recently; after motorway driving in heavy rain, then when trying to restart after an hour to 90 mins approx (engine block warm to touch but not hot or cold), the engine just turns over without catching. Both times I have eventually managed to start after leaving it a while - but as it's my only car I don't want to get stranded.

Prime suspect is the crank position sensor failing, but are there any other possible areas to look at ? (especially considering damp conditions)

Any help (or confirmation of crank sensor) greatly appreciated.

 

I would have said the egr valve if it was half an hour. After an hour, though, I would suspect the fuel return, and/or the fuel pressure regulator. I believe these have been touched on more in previous threads, so search away!

 

Just have a look at the front of the engine, on the RH corner.

There is the CAS (Crank Angle Sensor) loom connector. It is vertically mounted, and the "gunk/oily mist/road junk, all gather in/on that connector. Seperate it, which can be fun, clean it out thoroughly, spray with WD40 or similar, and replug. Fixed mine.

I did a write up on that and I "think" it is in the stickies at the top of this section.

 

Hi t140pete,

A few things come to mind and we certainly have to wonder if driving in the rain is an important clue.

To answer your first question, yes, a failing Crankshaft Position Sensor (CKPS in Jaguar X300 terminology) can cause intermittent starting issues before it fails completely, and as Grant mentioned, cleaning its electrical connector is well worth doing. I personally recommend using zero-residue Electrical Contact Cleaner since WD40 leaves behind an oily residue that adds resistance to electrical circuits. Probably not a problem for the CKPS, but a definite problem for sensitive circuits like the MAFS, TPS, O2S, ECTS, etc.

Another possible suspect is the Camshaft Position Sensor (CMP), which the Engine Control Module (ECM) refers to initially to establish ignition timing within less than 1 full rotation of the engine. If the CMP signal is faulty, the ECM then refers to the CKPS, but it can take up to 30 seconds of cranking for the ECM to determine correct ignition timing through trial and error based on the CKPS signal. So one test you can conduct the next time the no-start occurs is to crank the engine for at least 40 seconds to see if it will eventually start. If so, suspect a problem with the CMP.

Another possible suspect is the Engine Coolant Temperature Sensor (ECTS). The ECM uses the ECTS signal to determine cold-start fuel enrichment. If your ECTS is sticking at the "full hot" reading, the ECM will not apply cold-start fuel enrichment and a cold engine may have difficulty starting, especially if some of the other components have drifted out of spec. You can test the ECTS behavior with an ohmmeter - its resistance should change significantly between engine cold and engine hot temps, and there is a resistance chart in the Engine Management System (EMS) manual.

Malihide mentioned the Fuel Pressure Regulator (FPR), which works with the check valve in the fuel pump canister to maintain pressure in the fuel supply line and fuel rail. The FPRs do fail over time, typically leading to long cranking times and sometimes to vapor lock, which occurs when the engine is shut off and the failed FPR allows the pressurized fuel in the rail to suddenly de-pressurize. The fuel boils and becomes gaseous, so the engine will not start. But this is typically only a problem when you try to restart the engine within a short time after shutting it down. After and hour, the fuel will have certainly condensed back to liquid, so I don't think this is your primary problem, though a failed FPR may be a contributor to your issues.

Back to ther rain as a clue.... It would be worth checking for water ingress at the electrical connectors for your ECM and Body Processor Module (BPM). Both are known to cause intermittent problems.

The last thing I can think of is a weak battery. If the voltage while cranking falls much below 11V, the ECM will not trigger the ignition to fire. Assuming that the extra load of driving with headlamps and windscreen wipers may be drawing your battery down and heating it up, perhaps the battery is having to cool down before it can supply enough voltage and current to satisfy the ECM for a restart. It would be worth having your battery load tested because Jags are notorious for being unhappy with anything but a 100% healthy battery.

Cheers,

Don

 

Thanks for your replies, gives me some ideas just in case. I have replaced the Crank Position Sensor today, and tried to re-start the engine both an hour and two hours after a good drive to get everything up to temperature - both times with instant success

I also cleaned all the easier to get at sensor contacts (with proper contact cleaning fluid)

The results make me a bit more confident, but I will have to drive in a deluge again to be sure (no problem finding rain in Northern England at the moment) - fingers crossed