I have an 88 xjs v12. I can start the car but after about 30 seconds to a minute it appears to be loading up with fuel as evidenced by the blue smoke from the exhaust and stalls. It will start again but only after sitting a few hours. This problem first surfaced after exiting the HWY at 70 mph. While sitting at the traffic light at the end of the exit the car stalled and would not start. After I had it towed and a few hours later it started, ran for a few minutes and then stalled. Since then it will start after sitting a few hours but is progressively getting worse and will not run as long before stalling. I've checked the ignition, fuel pump, injectors with a noid light, vacuum line to ECU MAP Sensor, resistor pack, water temp sensor, air temp sensor, etc. Has anyone experience this issue before? Thx Rich

 

I had a similar problem with my X40 or X300 (can't remember which). It would stall after a long run and not start for several hours. It turned out to be the return feed from the fuel rail into the fuel tank is too close to the pump inlet - so the fuel heats up and vapour locks in the pipe.

The solution was to always refill the tank before it reached 1/4 level. On a long run starting with a full tank, refill as it passes 1/2 level. That way the fuel in the tank doesn't get too hot. Try it.

 

Remove the vacuum hose from the fuel pressure regulators. Any raw fuel dripping? If so, you have a ruptured diaphragm ....and raw fuel being sucked into the engine.

Or......

How about a faulty pressure regulator causing excessive fuel pressure? That'll cause over fueling. A fuel pressure test....sort of a hassle on the V12....will be needed to confirm

Cheers
DD

 

Welcome to the forum Rich,

I've moved your question from General Tech Help to XJS forum. This is the place to post technical questions about your model.

Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

First and foremost, welcome to the forum.

Doug has a good suggestion, and quite common.

"Blue smoke", is usually engine oil related. Excess fuel is generally a "Dark Grey/Brown" colouring.

A fuel pressure test is mandatory to stop the guessing.

Also, pop the 2 air filter elements, get a clean rag, soak it in solvent, open the throttle discs (engine OFF obviously), and clean ALL the black goo out of the inside of the 2 throttle bodies.

You have "checked" the CTS, but what about the wiring, both inside the plug, and about 6" up the line where the ATS splices into it.

Next would the TPS. It is dying. A simple test is well documented here for it. Age is its enemy now.

 

Grant beat me to it , and its all good advice

as its blue smoke, i would also pull the oil breather filter on the front of the left head, this has a rubber hood , and underneath is a gauze filled can filter , this blocks and can cause a back pressure stopping the engine from breathing correctly , then the oil can be forced past the pistons and burned off , they can be bought new if required

just remove this filter and soak in solvent and ensure its clean and dry before putting it back in

BB

 

Good one BB.

I dont run that filter in any of the V12's, so its out of the remaining brain cells.

It reeks havoc. The filter, not the missing cells.

 

Thanks for your comments fellas, I still need to check the fuel pressure in the rail, weather permitting. The last time I check I didn't pay attention to the exact pressure, only that it wasn't super high or low. I have noticed the FF regulators are set at 2 different pressures, inlet at 46 +-2 and outlet 36+-2, I'm assuming this is important as the book says they are not interchangeable. As for the smoke, I'm sure its not oil, may have just described the incorrect color. The oil level increases the longer I troubleshoot the problem and smells like gasoline. Does anyone know if the 10 psi difference in rail pressure would cause the engine to flood? Also does anyone know where I can send my ECU for a bench check to eliminate it from the equation?
Thanks again, look forward to hearing your response.

 

It's the LH pressure regulator that actually controls fuel pressure in the rail. The RH (inlet) regulator can actually be removed/bypassed. I don't think the difference in ratings is the root cause of your problem.

AFAIK the only place to send your ECU would be AJ6 Engineering in the UK. Others might chime in with other suggestions, though.

Cheers
DD

 

This looks and sounds to me like an injector problem. 10 psi will not cause it, I believe. However, an injector loom short will hold the injectors permanently open and fill the sump in short order and stop the engine.

Remove the loom and replace it from Jaguar or rebuild it as BB's fantastic thread explains. If you have a marelli car, also redo the amplifier to dizzy looms.

I had exactly this fault about 10 years ago.
Greg

 

I'm currently dealing with this same flooding problem on my '89 w/Lucas.

Tomorrow I will swap out the fuel regulators and see if that corrects the problem.

I'm curious about how to troubleshoot the fuel injector harness. If there is a short will the injectors still pulse or do they just spray continuously?

Suggestions for testing would be greatly appreciated.

Thanks!

Mark

 

Safari
I had this exact problem. The injector loom is permanently live and the system earths to open the injectors. If the loom is shorting out unintentionally, the earthing causes the injectors to stay permanently open and flood the cylinders. At least three injectors will be open per short as they are wired ro fire in batches.

The symptoms are white-ish "steam" (actually fuel droplets/vapour) from the exhausts and loads of fuel in the oil.

If you have the original loom, 100% necessary to renew it, even if it is not the cause it soon will be! The loom OEM is clipped to the bottom of the V and gets cooked. When replacing it (very straightforward to do) I suggest you cable tie it to the fuel rail so it is in a far less hot location.

OEM injector loom is still available from JCP, or make your own (see BrakeBuster's great write up). Assuming the fuel regulators are not leaking fuel into the manifold through their vac tubes, there is nothing else that can cause a Lucas car to flood except this and a stuck-open injector. This last being the other thing to check, which means removing each one and testing it.

Greg

 

Hi Greg,

Thank you for the info.

I think I will disconnect the connectors on the existing harness and see if any of the circuits are grounded where they should not be. That should tell me if the harness is the problem or if its something else.

As you said, all of the old XJS's have brittle wiring and connectors and my '89's are no exception. They both need new harnesses. I might as well make two. I think I actually have an old '89 harness laying around that I can use as a template.

Looks like I know what I'm doing this weekend!

Mark

 

Today I verified that the Coolant Temperature Sensor was working properly and that the signal was reaching the ECU. I also confirmed that the fuel pressure regulators are providing the correct pressure.

I even swapped out the ECU with a known good unit. The flooding continues.

It appears to be happening mostly with the "A" bank. It looks like replacing the fuel injector harness is going to be necessary.

Hopefully I will have a good result by the end of the weekend.

Mark

 

this should be easy to check without actually disturbing anything on the engine

pull the 8 pin injector loom plug that goes to the power resistor mounted behind the right hand headlight ( in the engine bay ) and after identifying each wire check to see if there is a short to the ground wire in the loom from the injector feed , this will also help to identify which of the four groups has the short to ground , but you may have more than one short !

the way the injectors work is four banks of three injectors
A bank fire 1,3,5 together and then 2,4,6 together , same for B bank ,

this can be done in only a few minutes of testing , without the engine needing to be run

BB

 

I plan to test the harness today before I remove it from the engine but even if it test good I'm going to replace it just due to its age and condition.

Hopefully the wire and connectors I ordered will arrive before the weekend so I can get started in making the new harness.

Stay tuned.

Mark

 

Today I performed a continuity test on the existing injector harness. None of the wires are shorted to ground.

I was able to run the engine for a few minutes and made the following observations;

1. Both banks are running very rich.
2. Using my stethoscope I listened to all 12 fuel injectors. All of them had strong clicking sounds and none appeared to be stuck.

Considering that both banks are running rich I doubt the the injector harness is causing the problem. I thought that maybe the throttle position sensor was bad so I replaced it with a known good one and adjusted the voltage to .34 volts with the throttle closed.

Ran the engine again but it still runs too rich.

The only thing that I can think of that I have not yet checked and could cause all of the cylinders to be rich is faulty oxygen sensors. I will change those out tomorrow and see what happens.

Any other suggestions are greatly appreciated.

Mark

 

Just a thought: there is a a start-up enrichment timing device on the car as standard. To disable it, find the A bank water pipe that links the two water manifolds (it runs between the thermostat casting and the rear water manifold casting under the intake manifold). Follow the pipe to the rear water manifold, you should find a water temp switch in the rear water manifold with two wires to it. Pull these off and insulate them. This disables the startup enrichment system. It can be left disabled even if it does not help the problem.

Greg

 

Safari, If you have the time and patience I would be replacing your injector loom as a matter of course, its most likely not your problem but will end up being one. Greg had a great suggestion in disconecting the cold enrichment switch, again this should be done on all of them no matter if broken or not, then replacing oxygene senors wont hurt matters as well. Could you simply just have a dead rodent or a rag stuck in your air cleaner?

Back to the original post, blue smoke is oil burning, as others have stated, look at your breather lines, I think it has nothing to do with the fuel system, your simply drowning the motor in sump oil from what you describe.

Good Luck

 

Safari
You now have a few things to go at: The sump breather system (as Katoh says, this is quite a possibility given the blue smoke), the loom, the oxygen sensors, the enrichment timer system, and here is a fourth:

If the full throttle enrichment system is earthing all the time for some reason, this would make the engine run rich. On USA spec cars there are two devices that trigger the full throttle enrichment:

1) a microswitch on the rear of the capstan
2) a vac switch on the rear of the A bank manifold.
If the wiring to either of these is cracked and earthing unintentionally, or either switch is malfunctioning that would cause rich running.

Greg