Yes I have that problem where the V12 engine, in an XJ12 series 3 saloon, will not rev past 2000 rpm.
I have read quite a few posts here and have done / considered the following
FUEL Thought it was a fuel supply problem (as I have had that problem before) so I put a new fuel filter and checked and replaced fuel lines between the fuel filter and the only tank I have working. I also checked and cleaned the filter inside the fuel tank. I do not have the equipment to test the fuel rack pressure, I could buy the equipment, but I do not really understand how to attach the gauge.
EXHAUST it appears clear and no blockage. The exhaust from both sides is hot, but the left side of the car is hotter as I cannot hold my hand over it for long, the right side I can hold my hand in the exhaust for a long time. The exhaust smell looks similar from each side, perhaps a bit more moisture in the right side. The left side is smooth and continuos. The right side putters a bit coming out in a slight increases and decreases in pressure.
SPARKING I pulled some leads from plugs especially from the right side and connected a spark plug. Sparking looked good to my inexperienced eye with lots of sparking.
MANIFOLD pressure? I have not done anything here. But I am becoming inclined to think this may be a problem. Some time ago my GM400 gearbox stopped working and I now realise that the problem was not enough oil. I am now pretty sure that the membrane that connects to manifold was perforated and I never managed to have correct oil levels because the oil was passing to the manifold. I have oil in the air filter.
I have not done anything about the gearbox as first I wanted to get the engine running well again. However, I am not getting anywhere with the engine. I was convinced it was a fuel problem, and then a problem with one side not sparking properly. However, I am now thinking that perhaps the manifold pressure is wrong due to the gearbox problem and that this is also affecting the running of the engine?
Any way getting confused and looking for some help.
A fuel pressure test would determine if it’s a fuel related issue or not.
I have never done it, so I can’t help on how to attach the gauge, but there is a lot of info and pictures in the archives.
My two cents…
This possibly means that the left side works much harder, something worth investigating.
The ignition and fueling are global, i.e. there are not right or left bank specific, so the problem could be the plugs, wires, injectors or exhaust…
You should pull out some spark plugs, on both banks, and see their condition, colour and if there is some difference.
Condition of plug wires?
Also it’s worth looking inside your distributor cap for carbon deposits and also to check that the centrifugal and vacuum advance are working properly.
Oil from the tans can foul the plugs…
The manifold pressure sensor is inside the ECU.
Also worth checking is that its vacuum hose has no leaks (from under the balance pipe to the ECU in the trunk/boot).
An other cause could be the TPS. Kirby’s book has all the troubleshooting info.
Test the Air and Water Temp sensors, at the left side intake, temperature vs resistance (charts in the archives).
Removing the air sensor plug will cause about 10% over-fueling, removing the water sensor plug will cause massive over-fueling.
Short-circuiting them will have the opposite effect.
This might give you a hint.
I had hoped to avoid testing the rail pressure, but I guess it needs to be done to fully discount problems in fuel supply. I will look into buying the gauges and stuff needed.
It is interesting that you point out that much of ignition and fueling is the same for both sides. Which makes me think the oil from the transmission entering the manifold on the right side is the cause of that side not running well. I will as you say pull some plugs and have a look into the distributor. I had a look and pulling plugs needs to be preceded by cleaning the V, which is another painful problem. I will also have a good look at the air intake on the right and see if that can be causing problems.
I guess one side running poorly can cause the whole engine not to pass 2000 rpm? Or should I focus more on things like the fuel that can bring both sides down?
Ronbros, you have a beauty there, does not help me much, but does make me want to get my beauty running again! I am being asked to add a photo to my profile, I will see what I can do.
I will report back with any advances!
Thanks, Neil
With no other symptoms than a rev limit it sounds to me like you have a problem with your coil.
I don’t know the year if your Jag, so I can’t say with certainty, but I suspect you have two coils. The second, auxiliary coil would be mounted in front of the radiator. It has no high tension lead, the port is epoxied. It connects to the primary coil via two wires linking the positive and negative terminals of the two coils.
This coil is required to provide quick enough recovery of charge to supply a spark strong enough to jump the spark gap at revs above approximately 2000 rpm. Coils available at the time were not capable so the second coil was added. I think this coincided with the HE models compression increase which raised the required energy to jump the gap.
Check to see if you have dual coils, and if you do then confirm the wiring and replace the secondary if there’s no wiring fault.
The problem here is that common available replacement coils will be normal coils with an open HT port for the coil wire. If you mount that in the place of the original auxiliary coil it will arc to the frame and do you no good. I suppose you could fill it with epoxy and see if that works, but the better solution is to replace both coils with the later models single coil. This coil is capable on its own and simplifies the engine bay a bit.
I wonder if you will find oil in the manifold sensor hose/pipe. If you have been sucking oil from the transmission, it might have ended up settling in a low spot in the sensor pipe.
However, any fueling issue, I would still expect the engine to rev above 2,000 at light throttle. Which makes me think ignition …
Hello,
Aristides, I had a look inside the distributor, it all looked fine a little carbon. I cleaned all contacts. I missed the bit on vacuum advance, I will see if I can check that.
Jaguarrr, I had a good look at the coil and wiring and also in my manual. I am pretty sure I just have one coil. I have a XJ12 series 3 from 1991.
Mark, I will look into the possibility that the manifold sensor has oil. It can be ignition, but fuel is also a prime suspect, I had that problem before and this all started when I was low on fuel going up a hill so lots of power needed. But as I mentioned I think I have done everything about fuel except the important rail pressure test which I am getting organised.
Thank you, Neil
Very nice ronbros and surprisingly I am just getting to that point! (I should perhaps be awarded the slowest jag-lover worker award…)
I honestly have read a lot of posts and Kilbys book and I just do not get it clear on how to connect the gauge.
I see two options, one is to try and find and buy some connecting pieces and connect just after the hose that brings the fuel to the rail at circled point in the photo.
Another option would be to cut the longer straight hose where the fuel leaves the rail and put in a T with clamps at point I have indicated to cut in photo. This would obviously mean I would need to replace the hose. The hoses are hard and I should probably replace them. Reading about replacing hoses, am I correct to think I can cut / burn the old hose out and then just jam a new hose in and it will be ok?
Ronbos, I hate the look of my Jag to yours! What a difference, what a neglected mess I have. One day I hope I can advance to have my car at least look like I am taking care of her…
Neil, two things, make sure you use 2 spanners to undo the fuel rail,otherwise you stand a chance of twisting off the small diameter pipe, ask me how I know!
I would be inclined to repair the diaphragm from the trans sooner than later, if you are ingesting ATF its not going to help with the diagnosis.
Robin, Thanks for the tip to avoid more problems. Yes you are right I probably should address the diaphragm issue. I will clap the hose. The transmission does not work! No third gear and no reverse, I think I have completely burnt it out. My plan is to get the engine running properly again, before I open the transmission and see what is going on. If it is as suspected -
dead, I will put a manual transmission in. I went to a transmission specialist and he told me 3000€ perhaps more to repair. He then hurtfully said not worth spending that on an old car like that. Some people just do not understand. I can probably get a new manual transmission for that, but will need to make the change. But that would be an interesting project. But cannot bring myself to start if the engine is not even running well.
Another simple question, perhaps someone can help?
Struggling to get the old hose off and it is taking forever.
See the photo, on the right: an example of how it was and on the left: a mess trying to get the hose out of the collar and I just cannot get the old hose out of the collar.
I am thinking to just cut of the old collar and in so doing destroy the collar and throw it away and then replace it with a jubilee clip?
Good idea? Bad idea?
If I need to dig all the old hose out of the collar and use the old collar any tips on how to do that. I am going to damage it.
I have advanced a little, I have all I need to measure fuel rail pressure. I am doing my option 2, putting a tee in the hose after the rail. Robin, thanks, I used 2 spanners and a lot of force, they were solid with that kind of white aluminium oxide. With 1 spanner I would have broken something!
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
16
As I suggested before: My choice was to use a Dremel with a cut-off wheel to cut that cup in two circumferentially, separating it into a ring and a cupped washer. Slide the ring back for access to the hose for removal. Reassemble with new hose and the cupped washer only, throw the ring away.
DO NOT, under any circumstances, use a hose clamp on these fittings. It just causes leaks.
Neil,
I have removed and replaced all of the fuel injection hoses twice in the engine bay of my wife’s 1990 XJ-S convertible (is has a 5.3L V12 much like the one in your 1991 Series III XJ12). The first time was in 2005, when we got the car, and all the fuel hoses were original, hard, and some of the rubber was cracked and appeared unsafe. When I did this I removed all four of the special hoses with metal fitting from the car and took them to a local shop that rebuilds many types of hoses (fuel, air conditioning, hydraulic, etc) for cars and for other purposes. They cut off the old rubber hoses and the swaged metal fitting at the ends that hold the hoses on the metal pipes, put on new rubber hoses and then swaged new metal fittings on the ends but keeping the old pipes. These rebuilt hoses did a great job for about 10 years when I decided to restore the engine bay to a like new condition following an exterior bare metal repaint and installation of a new convertible top. I wanted a new original looking set of new hoses at this time but couldn’t find the OEM ones at the dealership or any place else. Fortunately for me MOTORCARS LTD in Texas, USA was selling a kit with four new aftermarket fuel injection hoses for the Jaguar 5.3L V12 engine that looked pretty nice. It is what they call “EAC9886.KIT” and “Fuel Return Pipe Kit” on their website. The purchase included free shipping so the total was $250 for the four hoses: fuel rail feed hose (CBC 7979), fuel return pipe, fuel rail (EAC 9987), fuel rail return pipe (EAC 9986), and fuel pipe (EAC7938) and some new NORMA hose clamps for the ends that do not have the swaged metal fitting. Some of those hoses are clearly visible in the attached picture that I took of the engine bay this April after I cleaned it up a bit.
I don’t know if just putting clamps on the ends with the swaged metal fitting will work for the long run. I thought you should know that you can get the original hoses rebuilt but also that new ones are also available.
I have no affiliation with MOTORCARSLTD other than as a satisfied customer.
Thank you. I got my wife’s 1990 XJ-S convertible repainted in 2014 and then put on a new convertible top with the help of a friend in 2015 so the exterior looked amazing as you will see in the attached picture.
However the engine bay looked pretty much like you would expect a 25 year old engine bay to look, and that didn’t sit well with me with the exterior looking so good. In addition, the engine coolant temp was running higher than it should, so I decided to remove and replace the radiator and then I guess I got carried away.
The attached picture shows what the engine bay looked like when I removed everything so that I could to adjust the valve clearances and before I started putting everything back in. I pretty much cleaned, polished, painted or replaced everything (hoses, belts, seals, etc) as I put it back in and also rebuilt a bunch of the wiring harnesses with new connectors.
Lately I have been working on the interior, redying most surfaces and rebuilding the seats with new leather seat covers I had made. I also got the interior birds eye elm wood professionally restored and it looks amazing after I reinstalled most of it.
Regards,
Paul M. Novak
1990 Series III V12 Vanden Plas
1990 XJ-S Classic Collection convertible
1987 XJ6 Vanden Plas
1984 XJ6 Vanden Plas
1969 E-Type FHC
1957 MK VIII Saloon
Ramona, CA USA
Paul it is truly a very impressive Jaguar. I aspire to have my Jaguar half as good. I hope you are not offended, but I am much more impressed by the engine bay, as Mark says, mighty fine.
It puts me off to post photos…
Perhaps I will remind you of when you started…
