XJS V12 morning sickness

Hi, check sparks & plugs (replace if necessary) check distributor cap Is oil press correct? If it's cold where you live and you have 20W50 consider to replace oil to 15W40 (less viscosity) best regards

"WayneC" escribió en el mensaje news: snipped-for-privacy@corp.supernews.com...

There was a global recall back in 86 that changed the fuel rails and removed the cold start injection system. If so there will be a block-off plate on the manifold below the center of the fuel rails.

These engines are a little cold blooded but should clear up after 45-

Make sure that the mechanical advance in the distributor is free and acting properly, then set timing to 18 BTDC at 3000 RPM with the vacuum advance hose removed & plugged.

BD

Fuel injected engines have a cold start fuel injector that adds fuel during the first XX seconds of running. Your engine's cold start system is not working.

Generically, these systems have a temperature sensor, a time-temperature relay and an electric valve to inject the fuel. It's a chain and any link can fail, the task is to find the defective link.

Hi,

I have had three Jaguar V12's I had this problem once (1981 XJS). It was the ECU.

Regards

ILT

Wow, apparently it could be a lot of things, many of which I probably cannot check (ECU, sensors, etc). I guess I need to light a fire under my mechanic somehow.

I do hear a hissing sound (vaccuum leak, perhaps) while it's cold, the problem being that I can't get out and look for the source of the noise while I'm busy pumping the gas pedal to keep it running... it goes away upon warmup. But, in fact I did have the cold-start problem prior to hearing the sound, which seems to have developed right after the exhaust pipes were R&R'd a few months back, although I don't know if there's a link.

Hi Wayne,

I would suggest that you check all hoses (about 1/4" rubber) associated with the Vacuum Advance System. It sounds as though one of these may have been pulled off during the Exhaust Work. These are located "in, around and under" the right hand air cleaner area. If there is more than one pulled off and it unclear which goes where, I can scan the layouts for you and send them to you by email.

Chris

WayneC wrote:

Chris, I tried to find a disconnected hose, but was unsuccessful ... there's a lot of hidden stuff in that area, and the noise of rushing air stops shortly after I get the car started and smoothed out enough to idle (after multiple starts and die-outs and much pedal-pumping) to allow me to get out and look, so I only get perhaps one minute to look for the source of the noise before it stops.

The noise is quite noticeable, seems to emanate from somewhere near the passenger side front corner of the engine, and the noise stops abruptly, as though it were simply switched off, rather than fading away.

Ambient air temperature was about 65 degrees F, so we are not talking about cold weather winter behavior.

BTW, on the driver side there are two small hoses coming off the center of the side of the air cleaner, while only one hose is hooked up to the corresponding nipples on the passenger side air cleaner (the second nipple has a rubber cap on it).

Any ideas what the noise could be?

I had similar problems due to a sticking auxillary air valve. This is on the lhs top rear of the engine. It mounts on the water pipe from memory and has an adjusting screw to alter tickover. When it sticks tickover tends to be fast until it warms up and hopefully frees. You can check it by taking it off and putting it in hot water.

The throttle potentiometer is another possible source. It wears in its early range as this is used most.

The advance retard of the distributer is by the centrifugal weights which seize up and by the vacuum module. Take off the dist cap and see if you can turn the rotor arm against a spring action just a few degrees. If it's solid apply oil drops sparingly to the screw in the centr after removing the rotor arm and keep wiggling gently until it frees. The screw has space under it for this purpose. Don't overdo the oil or use too light an oil or it may explode and wreck your expensive dist cap.

Check the vacuum module by sucking on the pipe to it and checking it moves. Also check all the pipes you can see on that rhs to see if any are split or have come off. A stethoscpope to listen for hissing may help.

Also check your throttle butterflies are correctly balanced and adjusted and aren't stick> Anyone have an idea why my 80K mile 84 XJS V12 HE runs horribly until it

Thanks for the reply.... for unknown reasons, the XJS suddenly began acting normal again (I guess whatever was stuck came unstuck), so the crisis has subsided, but I'll stash your advice away until the problem bites me again. I appreciate your advice.

Now my woes have shifted to my 89 XJ40, which refuses to fire up after sitting out in the rain overnight, then starts easily a few hours later. If it's not one thing, it's another.

Twojags wrote: