5.3 V-12 Won't start

Hi Bill ,
"Steve" from from Exotic Motors in Upland, CA (closer to me that you are) has been working on my XJS and made the diagnosis (I think you know each other). Steve said pre 1989 V12's used vacume advance and 1989 up V12's used Merilli ignition. He also mentioned the possibility of a sticky centrifugal advance.

If I have time later today I will look for the engine number. Thanks.

Morning Bob, give me the engine No of your S, The ignition retard/advance was failrly complex with lots of switches and a mess of hoses, and it changed at least yearly.

Doug thanks for that--exactly what I was thinking!!!!!!!!!!!!!

Edited on 2013-07-26 0:19:03

Victor: I agree with the others that the injector harness is a prime suspect. They are known to get very brittle with heat and disturbing them even slightly can cause problems.

Alan Seeling: Numerous possibilities. Are the injectors pulsing/clicking when you crank the engine? You might want to get a "noid light" (inexpensive) to check the injector circuits.

Rovert S: make sure to check the centrifugal advance as well. The mechanisms often seize up.

William: All the "HE" V12s had vacuum advance....albeit with a very complicated control scheme. I think it was some of the older pre-HE V12 with OPUS ignition that had the vacuum retard system.

Of course when the Marelli igntion was introduced on the HE engines the distributor had neither vacuum advance nor vacuum retard.

Discussing 3-4 different problems on 3-4 different cars in a *single* thread is a little confusing. Well, confusing for me, at least :-)

Cheers
DD

Robert, I do not think your S has a vacuum advance , all California cars had a retard system and only advanced above certain temperatures. Check it out, Bill

Aaahh - the joys of owning a Jaguar!

You leave home in a Jag but do not always come home in a Jag.

I recently purchased a 1986 XJS V12 which was running pretty good at first, although ran a little hot. Then, it I started having trouble restarting the engine. I got stuck away from home and luckily had a free 200 mile tow available from my AAA Premium membership. Turned out to be a defective fuel pump -a $510.00 repair. The "running hot" issue is due to defective vacume advance on the distibutor - another $600.00 repair after the NOS part comes in.

All the repairs & bugaboos are still worth it to me - Jaguars are fabulous cars!

.

A friend had a similar problem with his XJS V12 and it turned out to be a computer issue

47000 miles, 1992 XJ12. Ran well, then started stopping. Would run again after a while. Fuel pressure measured at 28 psi instead of 34. Finally stopped and had to fix it outside of home area. Changed fuel pump, filter and O2 sensor. It ran like a scared rabbit for 104 miles. When it stopped that time, I got it started again, but it only ran for a few minutes. After that it has never run again. Towed home from Yellowstone Park (600 miles and $2400). I replaced one of the coils, the A bank, in the rear, and moved it up the throttle stand, further off the engine before I started the diagnostics. Spark from each of the coils wires and then from a park plug on each of the banks. Fuel spews from the rail connection when disconnected. Reset the inertia button inside the car.
I have no other idea what to do. Any thoughts?

Victor,

George's call is by far the most likely possibility here, but one other thing to check is the wiring and connections to the Power Resistor module at the RF. It's very easy to damage or disconnect the harness from that module when messing with the Air Injection pump to release the belt that drives the A/C Compressor and Pump. If something happens there, bingo, no fuel injection.

Good luck!

I think you will find you have damaged the injector harness. It passes under the AC compressor. You have fuel and fire but the injectors are not discharging I think--you need to check and repair as necessary.