Hello
My jag has been off the road for a long time and I finally got round to trying to find the problem. When it was running engine was difficult to start and speed at tick over was between 1400-2000rpm in neutral and in gear was about 1200rpm and then I switched off the engine, I tried restarting and it never did.
I have no spark or injection. I have tested CPS and I found 1.3kohms resistance and while turning the engine I tested for a signal with multi meter on AC volts and I am getting 0.6V, I have replaced it and I am still getting the same reading. I have also replaced the ignition amp and tested all power supplies and earths for the ECM which were all good.
Also before I had FF 44 showing on VCM but now all I have is FAIL.
I am thinking there maybe a problem with the ECM?

Please can someone help

 

Hi pclarke,

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

First of all, please tell us the year and model of your XJ40, engine displacement, right- or left-hand drive and your country (France?) as all of those variables can make a significant difference in diagnosing the issues. For example the early cars have the battery in the engine compartment but the later cars have it in the trunk/boot, and certain countries have different equipment due to emissions standards and some countries offered 2.9L and 3.2L engines while the U.S. only offered 3.6L and 4.0L engines.

A couple of quick checks you can do:

1. To rule out a problem with the battery, check the voltage while cranking the engine. It sounds like you are handy with a meter. If your meter is fast-reacting, you can watch for the lowest voltage sag while cranking. If it falls much below 11V, the ECM will not trigger the ignition to fire. If the voltage across the battery terminals seems okay, check for corrosion on the terminals, then test the voltage at the starter and alternator. If you have a large voltage drop suspect corrosion or looseness on the various battery power connections in the car, which will depend on your model year.

2. Problems with certain critical relays are known. Corrosion in the base and on the relay spade terminals is especially common. The original blue Hella relays were not sealed against humidity and moisture and can corrode internally. Diagnosing relay problems will depend on your model year, but critical relays include the Ignition On relay, Main Relay, Engine Management System (EMS) Main relay and Oxygen Sensor Heater relay. Which your car has and their locations vary depending on model year.

3. Check that the inertia switch or immobilizer switch has not been triggered somehow. It is designed to shut off most of the car's systems in the event of a collision. It is a small black plastic rectangular enclosure mounted in the outside corner of the driver's footwell on left-hand drive cars. There is a small plunger-type button on the top of the case that I think pops up when the switch has been triggered. If it has popped up, press it down until it latches and try starting the car again.

4. Problems with the ignition switch are known. You can test the switch operation from its electrical connector inside the steering column cowl. The Electrical Guide for your model year will show which connections should be made at each switch position.

Other members will hopefully remember the things I've forgotten. Please check the battery voltage while cranking and the inertia switch and let us know the results, as well as the model year and engine/displacement and we'll try to help. Once I know the model year I'll post a link where you can download the Electrical Guide.

In the meantime please visit the New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum and post an introduction so we can learn something about you and your Jag and give you a proper welcome.

Cheers,

Don

 

Hi Don
Thanx for the info I'll hopefully be testing tonight and I'll keep you informed.
My xj is a 4.0l 1990 sovereign french version which I have had since 2010 and now has 160000km on it. As it was my second car when it stopped running I did look into the problem but now its been sitting for a couple of years and I would like to get it running again as I miss driving it.

Thanx

 

Hi
I finally got around to testing this weekend. First I cleand up all the earths I could find except the engine earth strap but I tested the resistance between body and engine and Im geting 0.0 ohms.
Battery voltage is staying about 11.2v while cranking all the places you suggested trying and I also tested on the ECM aswell and still about 11.2v.
Inertia switch and all relays are ok but I could not find the one for the oxygen sensor tho.

Thanx

 

AFAIK the 1990 doesn't have an oxygen sensor heater relay fitted.

Larry

 

Hi everyone !!!!

I have the same problem as well as the other member, I just drive the car and after a few days without using it the car wont start. Will some one help figure out what will be malfunctioning ? It seems like is no power at the plugs, and i don't remember seen any pick up at the ignition. the coil has b+ at the bolts. What else i must check in order to troubleshoot the problem ?

Thanks a lot.

 

This hasn't happened to me but I have read of occurrences where the rotor can short out to the distributor shaft and prevent sparking at the plugs.

If this is the problem, one temporary solution is to remove the rotor and put a blob of grease on the shaft and then replace the rotor.

The logic being that the grease will insulate the rotor from the shaft and temporarily prevent the short ....worth a try maybe?

Larry

 

Thank you Lawrence for your advice, I'll try it today and let you know !!!

 

Hey, you're welcome - hope that helps!

Good luck with it!

Larry