Hey everyone.

My 1992 V12 XJS has had an occasional no start since I've owned it. No real pattern to it but it generally seems more likely to happen when the car is hot. It used to throw no codes at all and the check engine light was off. The car needed new wiring all along the top of the engine so I just had a jaguar specialist shop build a new harness and repair anything else up there that looked bad/frayed. Car runs a lot better when running but it now throws these 3 codes, FF 23, FF 44, and FF 17, and still has the occasional no start.

Along with the wiring repair the O2 sensors are new as is the cap and rotor, plugs and plug wires. I know the car does have an exhaust leak at the right side exhaust manifold gasket but that is the only repair I know of it still needs. As I said it runs very well once it starts, whisper quiet and smooth. I Would LOVE any thoughts as to what may cause this no start. I have attached a video of how it sounds when it no starts for review as well if thats helpful:
Thanks,

 

That starting procedure for an xjs looks strange. Have you fitted a start button instead of using the ignition key ?

 

Yes, I should have mentioned that. The start button was mounted in the center console where the cigarette lighter usually would be by the previous owner.

 

I would begin by searching the archives (or googling) the three codes and going from there.

FF17, for example, relates to the Throttle Position Sensor. Don't be too quick to assume a component failure. Rather, I'd carefully inspect wiring to the TPS.

Same for the other codes.

The no start might come down to the crankshaft sensors. Fairly common. As far as I know they do not throw a code when they fail.

Others will chime in

Cheers
DD

 

I will second that Doug. The crank position sensors are at that time frame for needing replacement.

 

My 92 is prone to having a moment and throwing multiple codes all at once. It usually happens soon after the car has started. The fact that it throws so many codes at once makes me think its something to do with voltage. I have a switch connected to the earthing wire that can be found on the passenger side behind the ear on the center console where the air vent is. This switch allows me to reset all the codes without disconnecting the battery.

As for no starting, yes, I would go for the crankshaft sensor.

I would also, just for belt and braces add one or 2 more earths from the engine to the body. I added 2 on mine and it seemed to reduce the frequency of throwing codes, but I dont have solid proof it helps...... But it never hurts

 

Thanks all. Are doing the crank position sensors a big job? I've been searching the archives and it seems there are two, one on the front of the engine and one by the flywheel. Looking down from the top of the engine I haven't been able to locate the one on the front yet.

Also, not sure if it helps but when the car no starts sometimes it will start later on its own but it always will start with starter fluid. Does that make sense for it being crank position sensors as well?

 

Perhaps???


Possible scenario. Crank position sensor having a partial "hissy".
Result, weaker spark. Less volatile modern E10 doesn't ignite.
But, more volatile starter fluid, (ether) does. Once fired, it
either runs a bit on the ether, then quits or continues. No starter voltage drain, better spark.


Carl

 

Maybe the sound in my computer is off, but it sounded to me that the starter was spinning but not engaging the flywheel.

 

To me it sounded like a moose in heat, but then my hearing is going south

On a more serious note, have you checked all the grounds? It's the simplest of areas to check, and these cars are prone to corroding grounds, at least on the 80s model years.

The fact that you can always start it with starting fluid seems to indicate fuel related concerns, so especially check your grounds to the fuel pump and relays. A fuel pressure gauge left connected on the rail could confirm

A vapor lock could be culprit on the older models, but I believe a 90s era model is past that concern.

 

Thanks everyone. It took me a while but I finally got around to replacing the crank position sensors. The rear one was very stiff and I thought that may solve this issue but unfortunately things are no better. In fact over time the frequency of needing starter fluid to start has increased and at this point it requires fluid every time to start. Would love any other ideas. Thanks,

 

Mine (1992) will crank over but not start too. I think with forum help that its the battery.

 

I had a fault that caused multiple engine fault codes including FF17 (throttle position sensor), it was caused by cable from throttle sensor or possibly throttle idle switch dropping down from throttle pedestal and coming into contact with HT plug leads. It didn't cause non start however.

I agree that fitting extra earth connection from earth bus bar connection on bulkhead / engine firewall to top of engine can help if engine earth lead has corrosion problem which can cause FF44 (heated oxygen sensor - lambda)

 

Thanks Paul! I think that's next up. Do you happen to have a picture of how these are generally run? I am learning as I go on this car. Thanks again

 

Thanks, unfortunately my battery is new.

 

Update here. I've now run another earth strap to the top of the engine. I also had the fuel pressure tested and it is good. The fuel injectors are not pulsing at startup, but work fine once started. Any further thoughts on this would be very appreciated, I am at my wits end.

 

Have you changed the coolant temperature sensor?
There are 2, one for the gauge and one for the ECU; if the ECU one goes flaky (mine did) it can cause your symptoms.

 

Thanks Steve, can you tell me where the one for the ECU is? I only knew about the one on the front left of the engine. I have not changed it yet but will test it.

 

When I bought my car I had a lot of intermittent issues. I spent the day cleaning switches, all the plugs I could find and all ground points. 95% of issues went away. I would start with disconnect ground points, clean them and use conductive grease then reassemble.

 

In case you are still looking.
See this photo the sensor with one connection goes to temp gauge.
The two connection sensor goes to ecu. And there may be another on the other water rail to the other ecu (ignition and fuel ecu have separate sensor)
Near thermostat housing