Hi guys,
I have a 1990 Jaguar XJ6 that cranks but won’t start. I’ve changed the crank shaft sensor, rotor, distribution cap, ignition coil and the ignition module as well. They’re also not very cheap. It was my late uncle and I don’t plan on getting rid of it. It has 90k Miles only. I’ve tried everything and it seems not to start. I even did the whole starter fluid and doesn’t start. Tested for spark and have non. Any help would be greatly appreciated. Thanks.

 

Did you replace with new Crank Sensor, or used one?


When cranking - does the tach register about 200 rpm?


Do you have fuel pressure? Can you hear the fuel pump turn on?

 

Welcome to the forum Chris,

I've moved your question from XJ6 & XJ12 Series I, II & III to XJ40 forum. This is the place to post technical questions about your model.

Graham

 

Hi Chris,

Welcome to the Jaguar Forums! It's great to have you with us.

As JBzXJ40 hinted, a common indication of crankshaft position sensor (CPS) failure is that the tachometer reads 0 rpm while cranking. If the tach reads about 200 rpm, the CPS signal is probably plausible and not the cause of the no-start.

A common cause of cranks-but-won't-start is low battery voltage. If the voltage falls much below 11V while cranking, the engine control module (ECM) will not trigger the ignition to fire. You can test the voltage while cranking with a voltmeter, though many digital meters do not react quickly enough to display the true voltage sag - analog meters are better at this, and professional battery/charging system testers are even better.

A basic maintenance procedure on an XJ40 is to clean all the battery power connections between the battery and starter/alternator, including the jump-start terminal on the right side of the firewall (as viewed from the driver's seat). A small brass wire brush and zero-residue electrical connector cleaner are very helpful for this. Don't use sandpaper of any grit since scratches create air gaps that promote future corrosion.

On the other side of the electrical equation are the many ground points throughout the car. The most important ones are the battery ground cable where it connects to the right rear inner fender, and the engine ground strap which connects from a starter bolt to the front left inner fender. The engine ground strap completes the circuit for several engine-mounted components, including the spark plugs.... Other important grounds include the ones referenced by the ECM, two on intake manifold studs, and the one on the firewall/bulkhead behind the cylinder head. Clean those thoroughly with the wire brush and contact cleaner.

Make sure the king lead between the coil and distributor cap is in good condition and properly seated at both ends.

Some critical relays are mounted on a panel behind the front right hand knee bolster & glove box, including the Ignition ON relay (blue base) and Engine Management System relay (red base). You might try swapping the Cigar Lighter relay (white base) and Door Guard Lights relay (brown base) for the relays in the blue and red bases to see if the engine will now start.

The ignition switch (the electrical part, not the key barrel) is known to fail. You can test the switch at its electrical connector inside the steering wheel cowl, which is easy to remove, just a couple of screws on the underside. Use an ohmmeter to test for continuity between the correct wires per the schematic in the Electrical Guide, which you can download here:

Jaguar XJ40 Electrical Guide 1990

You can download the Engine Management System manual here:

Jaguar AJ6 4.0L Engine Management System/OBDI Diagnostic Guide

The Jaguar Daimler Heritage Trust has offered the original Jaguar Workshop Manuals on DVD-ROM, but the last time I checked it appeared they were discontinuing these items. You can download the British edition of the Haynes XJ40 Repair Manual (minus a couple of chapters) here:

Haynes Jaguar XJ6 XJ40 Repair Manual

Just in case your issue is more than a lack of spark, you can do a simple test of the fuel pump by turning the key to position II (ON) and listening for the fuel pump to run briefly in a "priming burst." The pump is inside the fuel tank, behind the rear seat.

Another thought is that the fuel in the tank may be old and contaminated, or the tank may be empty and the fuel level sender may be faulty, suggesting there is more fuel in the tank than there actually is.

Please keep us informed.

Cheers,

Don

 

Thanks guys.
If this helps, I was driving it down the street. Came to a stop sign and when I turned right, that's when it all over a sudden it lost power and would not start again.
Ill try all those suggestions and get back with you guys but I do know that I have a new battery in there and I also added a jump cable with another car running. I do have over 200rpm. I'll keep you guys posted.
Thanks.

 

Mine was doing that a few years ago. It was only in the afternoon, never in the morning.
Intermittently it would die, try to crank a few times, the would start after about 2-3 attempts.


One day I was in drive through at Wendy's for lunch and it died ( wonder if it had anything to do with gf telling me off for eating fast food night before..ponders ) while on a slight incline - XJ40's are not light. Luckily I was able to put it in neutral and let it roll back into a parking space. Had a quick look, found when I bang on the fuel tank, it started straight away, turned out to be fuel pump. Something to try next time it dies on you, see if it starts after a bang on the tank.


( went inside after to reorder food )

 

I would beg borrow or steal a ignition amplifier, the black box under the coil. I had one die on one of my ‘40’s Just make sure if you do try a substitute that you earth the body, the plug connection does NOT earth the module (ask me how I found that gem out $$$$)