Hello, I hope someone may be able to help!

I recently took my XJR for MOT, having been working perfectly for the last year.
During the fast idle test the tester did not notice that the fans weren't working (Fuse, subsequently fixed) and so the car did go into the red, switched off immediately it was noticed.

After cooling down he carried out the rest of the MOT without any problem, stopping and starting as required, first turn of the key.

Only failure point was high (very high) emissions!

After completing the paper work (leaving the car for maybe 10 minutes) I got in and tried to start.....turned over but would not run, it tried to start a couple of times but with no throttle response or attempt to idle.
Strong smell of petrol was also present along with an occasional puff of smoke from the exhaust,

We proceeded to prat about with it for an hour and a half, taking plugs out, cleaned put back in, checked Coils, took plugs out and turned over to clear cylinders (felt like flooding...).

Checked compression (due to running into the red) all spot on.

Eventually as the battery was getting low by this point we hooked jump pack onto it and it did actually limp into life, although only on what felt like 4 or 5 cylinders.
Turned off tried to start again same problem, so jump pack back on, got it running and managed to get it home.

Since then no joy getting it to start, I have been scouring forums etc and have changed what seem to be the usual items (Cam position Sensor, Crank Sensor and today after a long and testing day the Throttle position Sensor) all to no avail, exactly the same symptoms still present.

I have also changed the Coil packs (initially we thought they were at fault).

So does anyone have any ideas as to where I should look next (or have had the same issue)?

 

Crank position sensors are known to become flakey...giving poor running. Or sometimes fail outright.....resulting in a no start.

Does the tachometer needle bounce a bit while cranking? If not, your crank sensor is faulty.

Note, however, if the tach needle *does* bounce, it is not proof positive that the crank sensor is 100% good.

Cheers
DD

 

Thanks Doug, I will look at the Tacho when I try starting in the morning.


Latest news as follows:


Went to the car and put on a freshly charged battery this morning, hadn't done anything else, tried to turn it over, after a couple of turns it spluttered into life, not on all six but responding to the throttle, with a little gentle coaxing it picked up and ran on all six, revved properly and dropped back to idle as it should sounding as it always has.


I let it warm up to normal temp the turned it off to check coolant level (and to see if it would re-start)


No is the simple answer, back to square one, exactly the same symptoms as before, same smell of petrol etc.....


Could it be something to do with charge, both times it has started has been with either a jump pack or a fully charged battery?


I will check the Tacho as suggested


Thank you again Doug


Regards
James

 

The smell of fuel makes me wonder if the temp. sensor is not functioning and causing the engine to try to start in open loop when hot, resulting in flooding.

 

A couple of other simple things to check:

1. The ignition coil relay could be failing. It's the left relay in a group of three on the right inner wheel well (not the group of three mounted close to the radiator). Perhaps when the engine overheated the relay decided to go on the fritz?

You can download the 1996 Electrical Guide at the link below. Page 28 of the pdf file has a diagram of relay locations:

http://www.jagrepair.com/images/Auto.../jagxj1996.pdf


2. The Fuel Pressure Regulator (FPR) diaphragm may have failed, allowing unmetered fuel to be inhaled into the intake manifold causing an over-rich fuel mixture. You can check for this by pulling the vacuum line off of the FPR (a gold-colored cylinder near the front end of the fuel rail). Crank the engine and check for wet fuel at the vacuum fitting. If you see any, the diaphragm has failed.

 

I don't remember seeing any ignition coil relay?, the coil packs are fed from fuse #12 10amp in the RH engine bay fuse block this also supplies the started relay so if the engine is cranking over the fuse is good, there is a fuel injection relay which is grounded by the ECM to supply the fuel injectors that could be the one Don is referring to, but it sound like a battery issue low voltage when cranking the engine, see what the cranking voltage is anything below 9 volts will cause problems down the line on a Jaguar

 

Something you may want to check this is the ECM from a 96 XJR the pin that is grounded for the fuel injection relay has disappeared

 

I just went through this with My 97 XJR. It was the crank position sensor. I keep harping on this, although not sure anyone pays attention. These are a service item that does go bad. It is NOT a sensor. It is a electromagnet that produces a AC signal that the computer uses and converts to a timing signal. They are magnets guys. Magnets go bad with heat over time. Replace it, and my bet would be that the car starts right up.

BTW, my tach would "bounce" to 2-300 rpm during cranking with a bad CPS

 

Its a good point from supercharged its worth having a good CPS on your shelf as a spare, its know also as proximity switch its looking at the teeth on the crank gets a pulse every time one tooth passes, it knows its position as far as timing because one of the teeth are missing and it will count that miss also in every revolution. I always make a point of cleaning this area with a wire brush to make sure there is no engine crud on the pulley teeth to effect the signal.
I think a lot of problems come from distorted signal before it can be amplified by the ECM so screening this sensor's wiring is important

 

Hi superchargedtr6,

I completely agree that the CKPS is a service item with a limited lifetime. I learned early on in our Jaguar ownership that keeping a spare known-working CKPS in the trunk was cheap insurance.

However, I'm curious about your emphatic assertion that the CKPS is NOT a sensor. Yes, it is an electromagnet, but in this application it's not used as a "magnet" to attract other objects. It is used as a variable-reluctance transducer to sense the passage of the teeth on the reluctor or rotor, which, in some of Jaguar's documentation is actually called the "sensor ring."

Electromagnets are employed as sensors throughout industry, as are other simple devices such as potentiometers (e.g. the TPS), momentary-contact switches (HVAC blend door travel limit sensors), thermistors (ECT, TFT, IAT), and heated wire (MAFS). A device doesn't have to contain an electronic circuit or be otherwise complex in order to "sense" motion or other conditions and provide a meaningful electrical signal.

The fact that the device is called a Crankshaft Position Sensor by Jaguar and most other automakers should be strong enough evidence that the CKPS is no less a sensor than a wheel speed sensor, differential- or transmission-mounted road speed sensor, or any number of other applications for the good old electromagnet.

My two cents!

Cheers,

Don