XJ40 suddenly not starting

Suddenly while i got home. Changed sparks, rotor cap, CPS. Could it be the ECU ? Other ideas or tests i could do ?


Have you checked if you get a spark? Do you get fuel (are the spark plugs wet)?

Will check again, voltage at coil, spark and injector pulsing. I have also ordered a new ignition amplifier. I suspect the CPS but tachometer shows 100 rpm when cranking. By the way, where is located this ignition amplifier ? Thanks

Welcome Guerpillon,

There is a separate category for the XJ40.
With your permission, I will move you thread, you will find much more relevant info over there.

Best regards,

Yes, for sure, thank you for that.

Guerpillon …

If I understand your post your car had no problems and then all of a sudden it wouldn’t start at all.

As frustrating as that can be it’s probably one of the easiest problems to troubleshoot. Fuel - air - spark
Lots of information in the archives on this.

Screen Shot 2021-03-30 at 12.38.20 PM

The ignition amplifier module is number 4 (sits under the coil).

To add to the ignition amplifier, it earths through its body so make sure if you try a replacement that you either bolt it in place or have an earth wire connected to the amp and car body, don’t ask how I know :anguished:

1 Like

Robin …

OK let’s hear it … How do you know :grinning:

Had a mobile sparkie help me get an old ‘40 going after I had done some stupid things to the battery/ECU (reverse battery connections anyone)
I had purchased the car for $NZ700.00, replaced the petrol tank, repaired rust around the rear window (causing the replacement tank, luckily I had one sitting there)did a complete home repaint in my garage then drove it from Auckland to Invercargill for a charity run. I don’t know how much it cost me but it did raise a few dollars when it sold.

I had a notorious issue with one of mine having issues with the distributor rotors. They would arc through fairly often. Swap with a new one and they run again. Definitely check spark

1 Like

Thank you very much for this diagram and advice

I had the same issue as Larry Trom on my XJ40, rotor is common no start problem. There is a resistor in the rotor that fails and goes open circuit. Replace rotor and try again.

New coil, resistance tested, new distributor cap, new CPS, resistance tested, still no spark. 12V on + coil, lamp connected between + and - coil flicking while cranking. Tachometer at about 100 rpm while cranking, Andy other ideas ?

Guerpillon …

Did you take Larry’s wise advice and … “Replace ROTOR and try again” ??

When not getting spark, it has been the first thing I try, learning a lesson back in 1970 with an MG Midget. Spent a then, ungodly sum of $40 labor as a mechanic tried to figure it out for three hours. He was sooo pissed at himself when he discovered the rotor was at fault, that he threw it across the shop.

Will do, ordered a new rotor, thanks

Let us know if that was the problem :crossed_fingers:

In all these posts, Unless I’m missing something, no one mentioned checking fuel pressure at the fuel rail.

But he said he was not getting any spark. If he could get spark, and not starting then definitely
Check fuel pressure


Thanks, my bad, I should have picked up on that.