Hi everyone,

This past month i have had strange symptoms in my 1990. XJR which seem to be progressively getting worse. ONE POINT OF INFO, THE FUEL PUMP IS THE IN TANK VERSION.

It started about a month ago when during a drive, the Transmission warning light ( further refered to as: "TWL") came on, i got home using limp home and on restart it didn't come up again.

When trying to investigate a week later, the TWL, we could not get it to repeat it after a 2 hour drive. The same day, after i left the mechanic, the car stalled out and restarted 10 minutes later (i immediately poured start spray into the intake as i did not hear the fuel pump and it showed signs of a fuel problem i.e. the start spray made it come to life for a few seconds). I tried to wiggle connectors and the pump relay and the car restarted after 10 or so minutes on its own (no cause and effect with what i was doing to it) and i was able to get home.

After a few weeks of reluctant starts after its shut down (for instance i go to pick up a friend, he is late, i shut the car of, it refuses to start but after a few times of the key being turned and cranking, it starts normally). This happened a total of 5-6 times in the past month (not counting yesterday) out of those times, the worst time was a no start for 10-15 minutes after which the transmission warning light came on. After restarting once again the TWL did not come on. Due to these occurrences being relatively uncommon i was able to use my car every day until yesterday.

This brings us to today (or rather, yesterday), i went to the market up the road, as i was backing up to the parking spot at the store, the car stalled out. As it refused to restart, i pushed it in all the way into the parking spot and went shopping. After getting out of the store 10 or so minutes later, the car started fine and i drove home. In front of my house there was a bit of traffic so i could not park right away and as i was in traffic about 15 meters from my house, the car stalled and shut off. It restarted with the TWL right away but stalled again 5-10 seconds later and would not restart. I pushed it into my parking space and after 10 minutes the car started fine.

In total we have several symptoms:

1. Car stalls/ engine cuts while driving
2. The engine won't restart right away, but does so after 1-10 minutes of being left alone or furiously cranking
3. When shut off, the car sometimes won't start and when it does after 1-10 minutes of being left alone, sometimes it has the TWL.
4. The Transmission warning light comes on intermittently when turning the car on and goes off once the car is restarted. (the first time it came on while driving but this has not been repeated)
5. When the car stalled the first time the pump was not working (i did not check spark and fuel pump on other occasions as it was inconvenient).
6. it may be just me being paranoid, but for the past few weeks, when coming to a stop, the car felt jittery as if it wanted to stall at least 10-15 times or once or twice a day approx.

Any help would be appreciated, could these symptoms be related? Is it one of the sensors? Is it the fuel pump? Could it be the transmission? I had replaced the pump last year with a NOS walbro pump and have had no issues until about a month ago.

I use my XJR as my daily driver so this is important to me, if anyone has any ideas or culprits which would cause all of these symptoms it would be much appreciated as i don't want to go on an all out holy war against its electronics.


Thank you so much in advance,
Kind regards,
Stefan

 

I would start by checking all the ground wires for corrosion- even in the trunk. I would also try swapping the fuel pump relay with another and then try running a "hot wire" to the pump to see if it sounds right. Look at the electrical connections on the transmission, and lastly check the condition of your battery. A weak battery will make the car very unpredictable. It almost sounds like 2 separate problems ganging up on you, but dont get overwhelmed.
Hope this helps some. Good luck

 

Hi Stefan,

I'm sorry to hear you are having such frustrating problems with your XJR. Here are a few thoughts:

1. When you turn the key to position II (ignition ON but engine not cranking), can you hear the fuel pump run for a few seconds? It should run to prime the fuel system, and you should hear the faint sound of the electric motor in the fuel tank (from behind the rear seat). If you can't hear it, try Jerry's idea of removing the fuel pump relay and jump the terminals in the socket that correspond to relay terminals 87 and 30. This should force the fuel pump to run. Note that on your car, the oxygen sensor heater is in the ground path of the fuel pump relay. You can test the O2S heater circuit for continuity/resistance with an ohmmeter.

2. When the car stalls and will not re-start, does the tachometer/revolution counter register about 200 rpm while cranking the engine, or does it register 0 rpm? If it registers 0 rpm, suspect your Crankshaft Position Sensor (CPS). This is a very common failure point and it would be prudent to replace the CPS preemptively. It's right on the front of the engine, accessed from the right side of the car. The sensor is secured in its bracket with one screw with an 8mm hex head.

3. Low transmission fluid has been associated with stalling, especially when slowing to stop or to make a turn. Have you checked the fluid level? To do so, drive the car at least 15 or 20 minutes to get the transmission fluid fully hot. Park on a level surface. Depress the brake pedal and move the gear shift lever through all the gear positions (PRND32), holding each position for at least 3 seconds. This fills the passages in the valve body. Then put the transmission in Park and check the fluid level with the dipstick. If you can't get a clear reading of the fluid level, wipe the dipstick, reinsert, and repeat until you can get a clear reading of the fluid level on the dipstick. The level should be exactly at the HOT or MAX mark on the dipstick. Even a pint low (or high) can cause issues.

4. You can check for diagnostic trouble codes by turning the key to position II (ignition ON but not cranking the engine), then press and release the VCM button on the trip computer. Watch for any messages in the small display window below the speedometer where the odometer/kilometer counter normally appears. DTCs appear in the form of Fuel Fault or FF and a two-digit numeral, such as Fuel Fault 22, or FF23. If you have any message, write it down exactly as it appears and post it here and we'll try to help.

You can download a mostly-complete edition of the Haynes repair manual here:

Haynes Jaguar XJ40 Repair Manual

Cheers,

Don

 

Dear Don and Jerry, thanks for your replies and getting back to me so quickly and my apologies for the lateness of my reply, i have had a huge load of work this month so i didn't get a chance to do a lot, I am however using the holidays to take a look at my beastie.

Don, regarding your suggestions,

1. the fuel pump runs until i stop, and in traffic, i could not hear it *currently unable to reproduce stalling without getting into traffic - will try again in the following days. so i suspect the fuel pump to be not working when the issue happens - it has been changed for a walbro unit last year around this time.

2. The CPS has been changed two years ago, the revs happen and also, compared to that "type" of stalling, the car fires back after a few minutes, when the CPS was going, it was more like 20-30 minutes.

3. I have checked the trans fluid as described in the manual when i first had the trans light come on, it was slightly low, so i added half a quart or so and it was just slightly high - however, the date i added trans fluid was the first day i had a full stall, before that i only had the trans light come on once.

4. No codes on the VCM, on cold days i sometimes get the Oxygen sensor code/check engine light, which goes away after a few minutes, (advise if relevant to the situation) but currently, no fault codes.

And thank you i have both the haynes and the service manual.

Please advise if you have any ideas what could be the cause.

Thank you so much.
Stefan

 

Hi Stefan,

It's great to hear from you again, but I'm sorry your Jaguar is still misbehaving. Regarding the CPS, they are known for a variety of failure modes, so just because your old one misbehaved in one way doesn't mean your new one won't misbehave differently. At the very least it would be worth checking the CPS electrical connector for oil contamination and clean the sensor tip and crankshaft toothed reluctor wheel of any accumulated gunk.

Overfull transmission fluid can cause sypmtoms similar to underfull fluid, so you may need to remove some fluid. Follow the procedure I laid out in my prior post, which is the most accurate method of checking the fluid level (the manual version is neither as thorough nor as accurate).

One thing that would be easy to check is the fuel pump relay. I am not sure where it is located on your car, but on the early N/A cars it is located on a rail behind the glove box in a brown base. On the N/A '90-'92 cars, it is located on the brake pedal housing in a yellow base. On the '93-'94 N/A cars, it is located in the right rear corner of the boot/trunk behind the carpeted trim panel near the tail lamp assembly, in a black base.

You could try swapping the fuel pump relay with a similar relay from another, less important, circuit, such as the A/C compressor clutch. Bear in mind that the fuel pump relay is rated for high current and has a diode and resistor in parallel with the coil to help protect the associated transistors in the Engine Control Module from voltage spikes that occur when an inductive load like a relay coil is switched off. If you sway relays, try to identify one with the diode & resistor by reviewing the schematics in the Electrical Guide.

You can force the fuel pump to run by removing the fuel pump relay and jumping the terminals in the socket that correspond to relay pins 30 and 87. I use a large standard paperclip bent into a U to jump the socket terminals. You can wrap a piece of tape around the central section of the U if you're worried about receiving a shock, but it's not usually necessary.

Regarding the Transmission Warning Lamp, unfortunately there are no diagnostic trouble codes in the Jaguar implementation of OBDI and the ZF 4HP24 electronically-controlled transmission. The DTCs are mostly emissions-related. John Ping wrote an excellent diagnostic procedure for the '93-'94 cars that might be useful on your '90, possibly with some revision to take into account any differences in your car. You can find John's procedure here:

Jaguar XJ40 Transmission Warning Light Troubleshooting

Cheers,

Don

 

Thank you so much for the superb information Don.

I am taking things one part at the time and from the forum thd TPS looked like a likely suspect to me, especially as i havent cleaned the throttle body for thr 6 years i have had the XJR.

I have removed the throttle body today and will change the TPS as i have a brand new one ready to go, (un)fortunately not too much gunk to be seen on the throttle body so i am vary that the problem may be elsewhere.

Will fit the new TPS tommorrow and have a go and then report back here, but, just curious, is there anything special i should know regarding TPS voltage on a 1990 (1991 MY) XJR? Or should it be 0.5-0.6 v when closed and around 4.5-5v when open? This is from the book and otger forum posts i managed to find.

Would greatly appreciate any info or advice you might have for me.

Thanks,
Stefan

 

Hi Stefan,

I do not know the voltage specifications for the TPS on the S/C cars. One thing to be aware of when cleaning the throttle body is that you do not want to allow cleaning fluid to enter the TPS. In fact, one of the common problems on the N/A cars is that oil from the crankcase breather system settles in the bottom of the throttle body and drips down the butterfly valve shaft into the TPS, where it accumulates and interferes with the contact between the wiper(s) and resistive plastic trace(s). Many of us solved this problem by drilling drain holes in the corners of the TPS case and flushing out the interior of the TPS with electronic contact cleaner spray. By then leaving the drain holes open, the oil has a path to exit instead of accumulating.

Cheers,

Don

 

Don, thanks for your reply,

I replaced the TPS and set it with no problems, around 0.6v at closed and 4.75V at fully open.

We took the XJR out for a test drive, the throttle seemed a bit smoother, so we came back to my house and tried to switch drivers only to have it refuse to start.

This time the problem was more persistent, around 15 minutes of no start, spark was present, fuel pump was not coming on, fuel pump connector showed power on key turn.

After 15 minutes of looking around, one key turn, the pump became audible and the car started HOWEVER, with the transmission light. Turned the car off, restarted, no Transmission light.

At this point i would point to the fuel pump, but i am now sure that the Transmission light is somehow connected.

Any thoughts, or any previous threads with similar symptoms? i have not been able to find any.

 

If it isn't impulsing when you have power to it, you either have a problem at the flange connector on the top of the tank or a failing fuel pump. The other possibility is that the the fuel pump relay or the oxygen sensor heater relay (not sure if the 1990 has that) has failed. Either one will prevent fuel delivery.

Larry

 

Larry's suggestion to check the fuel pump relay and oxygen sensor heater relay (if relevant) is good. See my tips on the fuel pump relay in post #5.

Replacing the fuel pump is not as daunting as it may seem, but it's obviously easiest if the tank is nearly empty. The trickiest part of the job is disconnecting and reconnecting the fuel lines on the bottom of the tank due to their location above the differential. If you have to replace the pump, we'll offer some tips.

The transmission warning lamp will sometimes illuminate if the engine takes too long to start. I think it may be related to the battery voltage sagging too low while cranking.

If your battery is healthy, it would be worth disassembling and cleaning the battery power connections and ground points throughout the car, especially the battery cable terminals and posts, the negative cable ground/earth connection at the body, the B+ connections at the starter solenoid and alternator, and both ends of the engine ground strap. Also clean all the grounds referenced by the ECM and TCM. To clean the grounds, remove the nut and harness wire eyelet/ring terminals, clean everything to a shine with a small brass-bristle brush and electronic contact cleaner spray, allow to dry, then reassemble. Do not use sandpaper, as the scratches will promote future corrosion. The nuts do not need to be terribly tight, just snug. it is possible to overtighten the nut and snap the stud off the body.

Cheers,

Don

 

If you have the diagnostic tool it is very simple to check the transmission light! But as mentioned I think it is engine related and due to a long start the light is on.

 

Dear all,

thank you so much for bearing with me, knock on wood, been a few weeks of driving around and i seem to have fixed the issue, and thankfully it was a irritating but a simple one, allow me to caps lock it for future reference to anyone with similar symptoms,

CHECK THE MAIN P.I. RELAY.

it was the matter all along, switched it out and 3 weeks and 600km later, she's purring and happy!

On a side note, not sure why and how the tranny light came on so i switched the auto box CPU for good measure as i had a spare laying around.

Thanks so much for everyone's helpful suggestions, they have helped me so much, its members like you who keep these forums a treasure trove of information and make living with a classic a pleasure!

kindest regards and a beautiful summer with worry-free motoring to everyone!

Stefan S.

 

Just saw this post. Remember to replace ALL 'crappy-blue-Hella-relays'.