I'm not getting any spark at all. So far I've replaced my Crank position sensor with a used one and a new one. Both tested within range using an ohm meter. When cranking the engine,I don't get anything on my tachometer though. I've also tested both primary and secondary on the ignition coil and it seems fine. I'm getting power to the coil and also to the ignition amplifier. Would the amplifier keep the tachometer from registering while cranking the engine? Is there any way to test the amplifier? Could I have a bad ECM? Is there another way to test the crank sensor?

 

I think you could test the crank sensor by backprobing its electrical connector and connecting a scope or a meter with a duty cycle setting that will show the percentage of on time or milliseconds of on time, but you would have to do your measurements while cranking the engine.

I'm not sure if a problem with the amplifier would prevent the tach from showing 200 rpm while cranking - you might check the schematics to see if there is any connection between the CPS and amplifier. Off the top of my head I think the CPS connects directly to the ECM.

If the battery is weak and the voltage sags much below 11V while cranking the ECM will not trigger the ignition to fire.

 

Voltage is right up around 12.25 volts. I've been using a booster while testing and cranking so my battery doesn't drain. Aside from having it towed into a local repair shop to have that sensor tested I'm just stumped. Is it possible the ECM just died?

 

Way out in left field here but is the inertia switch triggered?

 

I wish it was. That was one of the first things I checked!

 

It's possible, but very rare. It would be worth checking the electrical connectors at the ECM for any signs of water ingress or corrosion.

It is also possible that used and new CPS's you've tried are not working. Non-working new CPS's have been reported.

I can't remember if we've discussed the grounds but corrosion on the ground points can cause problems. It would be worth cleaning all the ground points in the engine bay, especially the ones used by the ECM (two on the intake manifold and one on the firewall/bulkhead behind the cylinder head). I have a number of photo albums on the ground locations and how to clean them - see the link in my signature.

P.S. I added the year and engine of the car you're working on to the title of your thread so we wouldn't have to keep asking you.

Cheers,

Don

 

I don't remember the wiring for the 3.6 but I had a customer with a 1990 4.0 that had no power to the positive side of the ignition coil. It turned out to be a connector under the right side under-dash panel. It was a white/pink (WK) wire so I put a jumper around the burnt connector to get the car going again.

This was 10 years ago so I don't remember the details.
Check to make sure you have power to the ign module and coil. (same power source I think)

bob

 

I'm getting battery voltage to the ignition coil and module with the key turned on. I've come to the conclusion that the crank position sensor isn't being read by the ECM or the signal isn't reaching the ECM.

 

ok, maybe you hooked up the "new" plug backwards or something - try reversing the connections and see if you get 200 rpm on the Rev counter - try unplugging/replugging the ECM too.

 

I can try unplugging and plugging in the ECM but the CPS can only plug in one way wsith the round style connector on an '88.

 

I thought you'd modified the connector and asked which wire was which in the other thread, but no eh?

 

I did change out the connector on one of the two crank sensors but they use the same color coded wires in both connectors.

 

Update: Well,managed to get out today and take a trip to one of the salvage yards about an hour away. Seems this yard is the only one with an XJ40. I picked up an ignition module as one of my last resorts before having this car sent off to a specialist to figure out why it wasn't getting spark. Well,it's amazing what a little two inch ignition module can do. I now have my spark back! It was so exciting to hear that roar of the 3.6 liter come back to life after weeks of trying to track down the problem. As a bonus,while at the salvage yard,the car had a Jaguar heavy duty car cover that I purchased for just $10. Everything just managed to fall into place today!