Hello,

1992 Jaguar XJS V12 5.3 cranks but won't start.

Car had recently received a replacement engine and ran beautifully one week ago before being parked outside in the snow against my wishes.

Checked today and car has fuel pressure at rail, spark from both coils, spark to all 12, fuel injectors are firing in sync, cts and air temp sensors are reading properly - even at ECU plug.

I'm going crazy here. Any ideas?

Thanks,
J

 

Maybe it just needs a bit more time to process the Packers loss after dominating most of the game?

These cats have feels…

Seriously though if you have spark and fuel the only other thing is air restriction. Any chance the snow or ice is preventing air intake? Have you tried removing the air cleaner and spraying starter fluid directly into the throttle body to see if you get any attempts to fire?

 

I initially thought the same thing so I moved the car into my heated shop and let it sit for 6 or so hours in the 70° F. Still no change. Tried starting fluid in both throttle bodies, no change.

 

Then, for whatever reason, there is no spark. Have you pulled a plug, held it against the engine with some insulate pliers, and had someone crank while you look at the plug to see the actual spark at the electrode?

 

Yes I have. There is a strong spark. I have tested on multiple plugs on both banks. All have given same result, strong spark.

 

jblessing,

it's really difficult to see how starting fluid wouldn't cause it to at least cough?

Was your spark test with the actual plugs removed from the engine and seen sparking when cranking, not just a spark at the end of the lead or with a spare plug inserted?

My initial thought was that you must have either:

- coked / wet plugs that are preventing sparking inside the cylinders
- flooded cylinders preventing anything combusting in there
- no fuel being injected when cranking (have you checked for fuel spraying from an injector when cranking?)
- stale fuel (maybe water in the tank after the snow?) with so much ingested into the engine that it even prevented starting fluid from combusting

I'd pull all, or as many as possible plugs, examine them, clean them, spin the engine with the fuel pump disabled to clear the cylinders, replace the plugs, check they are sparking when cranking, keep the fuel pump disabled, spray starting fluid when cranking and see if you can get it to cough. If it then does, I'd enable the fuel pump and crank and see if it starts.

Good luck

Paul

 

could be a failed ECU

 

Just wanted to update everyone.

After spending yesterday doing in depth diagnosis, we found one bank of injectors not firing. After every test we could think of, we found that there was a short somewhere in injector harness 1-3-5 on B Bank. We believe that some of the insulation on the harness fell apart due to the brutal cold here outside. Mix this with snow, and its not a good situation. This short took out the ECU at pin 11 causing a permanent grounding issue. We are swapping the ECU in the trunk today and bridging pin 11 to 29 in the trunk to give power and ground to the B Bank injectors. Will update after its together and see if we have a good running car.

While it was not running on all 12, we managed to flood bank A which is why we had a no start. After pulling bank A plugs and getting rid of the excess fuel, we have gotten the car to run on 6 cylinders.

Thanks for all of the help,
J