My engine bay had a fire and a lot of the electrical wiring is toast. The person before me started replacing the wires and I should have what I need to finish the job. I'm worried about what caused the problem because I don't want to go through all this trouble just for it to burn again. I'm thinking it started in the front passenger side but I have no idea. The smog pump is frozen and will not move but I don't know if that had anything to do with it.





Front passenger side








Rear passenger side

 

lack of maintenance is the main cause

make sure the fuel system is perfect, and make sure the electrical system is perfect, both ignition and general wiring, anything less will result in the above

a well maintained XJS ( or any car ) won't catch fire for no reason


don't get me wrong, component failure will add to the risk of fire, but if the rest of the system is good, there is no reason for it to combust on the outside


BB

 

Ok thanks

 

It won't be easy, and no promises, but if you work carefully you might be able so see an area that looks like it burned hotter than others and that'll probably be where the fire started. From there perhaps you can narrow things down. Probably a direct voltage-to-ground short circuit due to chaffed, cracked wires.

Cheers
DD

 

Any misfire will cause the oxygen sensor to see excess oxygen. That then causes the fuel controller to richen the mixture in an effort to burn the excess. The excess unburned fuel causes the catalytic converters to get very hot. Excess fuel and glowing cats are a disaster waiting. This is a common cause of XJS fires. I watched this scenario take place on mine. I caught it before any fire. My cats were melted. Just make sure all 12 are firing correctly.

 

The biggest problem with the XJS engine bay is heat and age.

After 25 to 30 years of high heat conditions many of the electrical harnesses and rubber fuel lines become brittle and deteriorated. Engine fires are usually a result of leaking fuel lines or electrical shorts.

If you have had an engine fire I would recommend that you replace all of the old engine bay harnesses and all of the rubber fuel lines. Especially the short lines that go to the fuel injectors.

This is a lot of work but completing it will ensure many years of operation without fear of future fires.

Mark

 

Compared to some of the engine fire pics ive seen posted, this one looks minor. So while deteriorated fuel hoses are often the cause, yours appears to be electrical. If you dont already have it, google and download "kirby xjs help", his free book goes into good detail on causes and prevention

 

forgot to mention, someone did a good writeup on this forum of replacing the injector harness wiring, you may want to search for it. The smog pump along with the air injector rail may be jettisoned if you and your state/county does not care avout emmissions on older cars. Its unlikely that a frozen smog pump caused a fire, though it looks like youre missing the belt

 

I was reading about an engine fire that was caused by brake fluid leaking on the exhaust, Who knew?

Leaking injector hoses. The little short ones will crack and leak on the manifold.

The fuel rail may crack and leak at the welds.

There are more I am sure

 

all the items mentioned above would come under regular inspection and assessment of the under bonnet ( hood ) condition of all the critical components, maintenance also includes recognising when something is about to fail due to its visual condition ,

who lives with leaking brake fluid ?? talk about a death trap

i did a thread on how i rebuilt the injector harness to my own V12 last summer

https://www.jaguarforums.com/forum/x...ctures-127573/

hope this helps

BB

 

The ignition amps (the two flat small electrical black boxes sitting on the bodywork above the radiator/air conditioning matrix) can be a pain. They can start to fail and suddenly shut half the engine down while the other half stays running. This pumps lots of unburned fuel into the cats on the non running side and either obliterates the inside of the cats or catches fire in the cats if the amp re-sparks the ignition and the accompanying excess heat from the fuel burning inside the cats starts to melt the underseal on the bodywork around the cats. If your car suddenly drops power and sounds like a truck, pull over immediately, switch it off and recheck the wiring harnesses on the ignition amps. It happened to me once driving from a concert in downtown LA and even though it was momentary is remember seeing a pile of red hot catalytic converter material shooting out of one side of the exhausts when it re-fired. I always have a fire extinguisher in the trunk just in case.

 

How about some pics of the rest of the car?