Perhaps the hoses are some how misconnected so crank case fumes are being allowed to collect in the dist...at some point a combustible mixture is established and it ignites under the presence of spark. My years of boating experience has taught me that crank case vapors are more combustible than they most people expect.

Typically a vented dist has port vacuum applied to the one tap and a fresh air supply downstream of the air filter on the other tap. Both hoses should have check valves to ensure a one way flow of the air stream.

 

OK, I'll take a stab at it as well.

I'm sticking with a Marelli failure. You say that the cap, rotor, plug and coil wires have been replaced. Is it possible the spark plugs themselves are an issue? If the plugs are not properly gapped, or if they are old and the gap has opened up, this can put stress on the rotor and cap leading to a Marelli failure.
Best of luck and let us know what you find.

Bill

 

I agree with you and also think that proper maintenance can prevent most problems. Checking the cap/rotor/plugs every 15K, coolant changes every other year, etc.

 

After the first incident I replaced all plug and coil wires, rotor and distributor cap. Inside the distributor is very clean...no sign of engine vapors or such. This time I had the car hauled to John's Cars in Dallas and he like me has doubts about gas fumes building up inside because there is no sign of an explosion even a minor one. We can fine no service bulletin that addresses this problem. I really appreciate all responses.

 

Just to recap:

• Have you done the Palm fix?
• Are the cats and lamda sensors definitely 100% with no chance of one having been partially blocked/wrecked by a dizzy fire failure?
• have you (as I think an earlier poster suggested) rigged up a new suck pipe direct to the airbox and replaced the inflow pipe and filter?

Finally, my suggestion is to carefully check the crankcase breather system and ensure it is all unblocked and functioning 100%. If all this is done, I think you have a good chance of having fixed it!



Greg

 

Next i would check the fuel system. With that many connections, one could be leaking. Fuel leaks can come and go. If the damage to the dist is external is was like caused by a fuel leak. Often fuel leaks occur when the vehicle is cold, the fuel collects, vaporizes and at some point ignites. Have your mechanic pressurize the fuel system by powering the fuel pump then physically check the connections and wiggle them by hand. Often the pump can be dead headed thus increasing pressure and exposing a week point.

 

As my engine is already mainly in pieces, I though I'd check the distributor at the same time. Safe is safe...







Does that look as if a fire is due? Looks kind of like a good setup. A little bit of white dust but otherwise it looks all fine. I'll still be replacing the hoses with some silicone ones with high temperature rating. Whilst it is in pieces a clever thing to do

 

That made is Italy badge is a real concern!!!!




Looking at the pics it is very had to tell particularly since mine is Lucas. For the price of a cap and rotor, plugs and leads its worth doing the lot for piece of mind. That has always been my approach and I have yet to go up in flames (touch wood).


Quite a bit of oil build up crud just below the cam covers and above a hot exhaust manifold though. I would remove that asap if were you and track down the source. Leaky 1/2 moons would be a prime suspect.

 

Here is a cut and paste from Kirky's "Experience" book, found on page 164 (in the Marelli failure section).

THAT’S NOT ALL: George Schulte says, “I came out of a store after 15 min of shopping to see smoke billowing out of my hood. When I opened it the flames were pretty well involved. Luckily a fire extinguisher was close at hand. The fire began from the center of the distributor cap. The lighter cap besides being cheaper and lighter is also flammable. I noticed some arcing around the center hi voltage lead but didn't think too much at the time because the car was running fine. The plastic is not hi temp and the entire cap caught fire which spread to the rest of the wires in the area which spread out and melted the fuel hoses.”

 

Made in Italy isn't my concern

But yeah, the oil sludge is going to go. New half moons, new gaskets, etc. HT-leads and plugs came in around May. So they are all fine - only driven about 500 km on them so far this year!

 

A final "Thank you" to all who have responded to my search for an answer to the second distributor fire in the last 5,000 miles on my 92XJSV12. You all have me convinced of the lack of proper venting in the distributor. I could never find any service bulletin from Jaguar addressing this. In answer to other suggestions I will let you know that all hoses around the distributor are new. The engine bay is almost show quality and could be so with only a little attention. The only missing decal from the engine bay is the one atop the brake fluid container and I still have it in the console. Again, thank you for the info and your patience. Should have the car back on the road by this weekend.

 

Please read Kirby Palm's book. Especially the part about the Marelli ignition system.

Available as a pdf or for download here - http://api.viglink.com/api/click?for...m&txt=XJS_BOOK

Starting on page 159 and going through page 172.

This distributor and rotor are notorious for failure just as you describe.

 

Same thing happened to me one time. Once power was lost, I stopped immediately and had as an emergency a fire extinguisher. I pulled the Dis cap and the rotor had a small burn hole through rotor. The dist cap was ok and nothing burned there. When I put the new rotor on, I filled it with silicone and so far touch wood its working well. ALWAYS carry a fire extinguisher that is full. When the one bank shuts down, there will be a fire if you keep driving it as fuel is being pumped into the dead bank cat converter. Yes It was a Mirelli cap and rotor. I will always carry a spare rotor and Dis cap, wires and plugs.

 

Final note to distributor fire for the second time in 5,000 miles on my 92 XJS 12. Replaced all wires, plugs, distributor cap, rotor and pinched hose in the vent system. The darn thing was located on the top edge of the left fender well where the bonnet nests when closed. Have driven about 500+ miles and so far no problems. Thanks again to all.