84 xjs v12 , was running good, started fine. Parked in garage- negative post of battery off, battery tender on, 8 days later replaced pcv valve and cleaned mesh filter. then 6 days later, put neg cable back on- engine starts- lots of white fuel smoke out the exhaust, strong gas smell, engine runs rough, and runs at 1800 rpm for about 3 min. will not restart until sets for hours then restarts runs rough and gas smeel and white smoke. tested fuel pump, checked vacuum hoses , same thing, now have quite a bit of fuel in the crankcase..
Need to get some thoughts on where to check, and I know i have to change oil , too much gas in oil to be safe.
Thanks

 

Sounds like a stuck injector, or maybe one of the fuel regulators got a hole in it and it's leaking gas thru the vacuum line into the intake manifold. Pull the vacuum line on each regulator, and see if there is gas in it.
Is white smoke coming out of both sides, or just one?

 

Is all of the smoke coming out of one side/bank?

Never mind that... I think you may have ended up sucking a ton of built up oil into the intakes and now your plugs (maybe O2 sensors if fitted) are fouled out and up.

Pull the easiest plugs, inspect them and clean them up, retry BUT eliminating the possibility of ANYTHING coming thru that crankcase vent set up. You can really just plug the hole somehow on the side of that tubing that goes across the top O the engine into the intakes and you shouldn't get an air leak that way.

Speaking of air leaks, are you sure after messing around with that tubing to the PVC you don't have and didn't create a massive vac leak? The high revs, 1800, is telling me lots of unmetered air is getting in somewhere.

I wanna know what other folks think, too. Curious stuff you got.

 

He says he's got gas in the crankcase. Doesn't sound like an oil issue.

 

It is NOT a stuck injector, it is a shorting out injector loom holding the injectors open all the time. The petrol in the sump is because the raw fuel is going down the bores in quantity. The only thing to do is:

• Remove the injector loom
• Remake it with new wiring and injector plugs - re-using the other end plug - or buy a new one from SNG Barratt
• Drain the oil and replace oil and filter.

After which all will be well!

 

I missed (didn't read) the crankcase part. My bad.
I need to be reading more carefully and completely.
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If it's white smoke you are burning coolant. You probably have a small head gasket leak allowing coolant into one cylinder when the car is standing. I had that exact same problem. Very distinct smell. If it clears after 10 minutes that is the problem. It will get worse if you don't fix it. PS no need to disconnect battery to use tender.

 

Fuel diluted oil, which he has, also causes white smoke. A coolant leak does not explain gas diluted oil.

 

Normally, yes; but when a V12 injector loom shorts out, what actually happens is that the quantity of fuel entering the cylinders is so vast, what appears to be white smoke is actually a huge cloud of depressurising fuel particles coming out of the exhaust. Believe me, I know, as it happened to me very early on in my XJS ownership when I knew very little about them, and also thought I had a blown head gasket!

 

But it was running fine when he parked it.

 

Yes. The injector loom fails due to age and heat. The head gasket isn’t going to fail when parked but the injector loom may.

 

The ignition control module tests bad, may have held the injectors open, or a short in the harness may have taken out the icm- so got a lifetime warranty icm, and will install, and remove the noi,se condsensor , if the harness is shorted and takes out the icm time time fix the harness and get another icm under warranty. BTW thanks to everyone!!!

 

Other than sending a signal to the ECU in the boot to confirm the engine is turning, I don't think that the Lucas box has any input to the fuel injection system, so I cannot see how it would hold the injectors open unless the ECU is also failing somehow. By the by, it is worth checking that you have the 16CU rather than the 6CU version of the ECU. If you still have the 6CU, it is a very good upgrade to chnge it to the 16CU, which is a far more reliable item.

 

Yep,

That Ign Module is for SPARK only, and tacho pulse to A) Tacho, B) Pin 18 of the ECU in the boot.

Has NO direct input to the Injectors, and the looms are NOT connected anywhere.

Some thing else to look into. The small vac hose that connects TO that ECU is known to split.

That ECU is s simple thing in its basic operation.
LO Vac = more fuel
Hi Vac = less fuel.
So, if that hose is split the ECU sees Lo Vac, and overfuels the system greatly.

Maybe its THAT SIMPLE.

 

Head gaskets can start to fail by having a small leak and allowing coolant into the chamber with no other symptoms. Strange but true. I have had one, an XJR. When allowed to stand for a few days they will emit white smoke when restarted. Eventually checking plug colors will show a very white plug in that cylinder. And eventually the head gasket will fail fully. But you would smell it. Doesn't smell like gas but the owner could be mistaken.

 

i agree with the above , especially fuel in the oil

but please remember, the gearbox modulator runs from vacuum , if the seal leaks, it can draw transmission fluid into the intakes and burn it

this will be very white smoke, and lots of it

but to be aware

BB

 

EXCELLENT point. That could foul the plugs, causing it to quit. Excess gas injected into the dead cylinders as cylinder after cylinder quits firing would get into the oil. That diaphragm is easy to check with a vacuum pump.
Lots of things to check.

 

Timely thread for me, mine started really smelling of petrol lately and smoking terribly from the A bank exhaust. thought head gasket too, freaked me.
Drained the sump today and noticed 2 extra liters came out! dipped a stick in it and proceeded to light a flame torch. Fuel in the oil.
New oil in and the smoke is massively reduced. Now to work out how the fuel is getting in there, but a far better outcome than a head gasket, phew.

 

It is extremely likely that the fuel is getting there because the injector loom is shorting out and holding the injectors open on A bank. As yours is a pre-HE (about which Grant is the expert and about which I know nothing) maybe it is a possibility one bank only can lose spark; but I have a feeling this is not possible.

 

I've been working closely with Grant on this one, once I figure it out I'll let the forum know, it's a strange problem. Not sure how many preHE are left down our way but I'm doing my best to keep this one breathing.