All,
Recently bought a well cared for and maintained XJS 4.0 ltr. A couple of weeks back my son started it up it ran rough until reaching temp. Since that I have been unable to start it. There is no spark or power to the Injectors. I have replaced the Crank sensor and coil still no joy. I am replacing the fuel relay and ignition amplifier today. Any body got any ideas as where to go next. I have checked all fuses and getting a bit lost as what to do next.
colin

 

Colin,

I wouldn't just start replacing items for the sake of it. There are very few items where you can't check if they are working or not before deciding to replace them. So don't replace anything else now until you know it's a failed item.

Also, you said that the car ran (albeit poorly when cold) and then now will turn over but you don't have ignition spark or power to injectors.

Whilst that could be a random number of different but unrelated items, it sounds more fundamental about power circuitry if its precluding both ignition and fuel injector circuits operating

So, perhaps start with some very logical diagnosis. The fact that the starter operates would SEEM to indicate that your ignition key circuitry is ok. If you start considering the fuel delivery side, when you first turn the ignition on, the fuel pump should operate for a short period. 3 key potential failures: the fuse, the relay, the pump. If the pump doesn't operate when you turn the key, start tracking the electrical side through those 3 items.

Same with the ignition side. Is the coil being enlivened? And then is it delivering back to the distributor during the starter operating?

If you approach both sides logically and separately, you'll pin down the problem. Plenty of people here to give you advice as you progress.

Good luck

Paul

 

Paul,
I have got a relay for the fuel system to try. Checked the pump by connecting to battery and it runs but, not when ignition is turned which lead me to a faulty relay thought.Thanks for the advice

Colin

 

Check the fuel inertia cutoff switch on the passengers side. There should be a button there, press that and see what happens.

 

Colin,

Very pleased to hear that you've got the problem sorted as per your other thread! Well done!

As suggested, a logical approach always solves the day. Your original post of simultaneously losing both spark and injector pulse implied that it would not be fuel pump, pump relay, inertia switch, coil or even CPS. It was always likely to be something that affected both sides of ignition and fuel together ie power feed from ignition switch or power feed in or out of the ecu.

Even if not necessary, at least you've now got a few new parts on the car!

Enjoy driving it!

Cheers

Paul