My wife's 2001 XJ8 VDP has died 3 times in the last 2 days. It tries to start (idles, sputters, dies - if you push the gas pedal - it won't rev, just sputters and dies). We had it in to a local Jag location (father and son repair shop) about 3 weeks ago when it died for the first time and they said it was a "fuse" - don't believe that was true. (and we got the car back with a dent in back of the trunk - frustrating). The problem came back - and if eventually starts (fuses don't "reset").

Seems to be a relay. If you let the car sit and cool, it will start again - or if you mess around switching relays - it seems to start. Doesn't seem to be the fuel pump - seems to be an injector or other issue as the car will idle occasionally.

I am thinking of simply replacing all the relays associated with fuel and spark as they are not that expensive. I can't seem to find the bank of relays that have to do with the A/C clutch, etc. - the fuse/relay diagram in the electrical manual shows that there is a bank of relays just forward of the windshield on the right and left side - apparently it must be buried under the dash or something because for the life of me - can't see where they are on either side (and it's hard to stick your head under the dash of a Jag!).

Appreciate some help/wisdom/experience.

The problem has ONLY happened after the car has been running and is hot and you shut it off - then you go to restart and it just sputters and dies, or idles roughly for awhile and then dies.

 

Is the CEL on? If so, have the codes read and post back here.

Somehow, I do not believe that changing the relays is going to have any affect.

Sounds more like a throttle body problem. Might clean it and check the duct work from the air filter to the throttle body. Also the part load breather tube from the left valve cover. It tends to get clogged up. Run a 5/32nd drill bit through the valve cover fitting holding it with a pair of vice grips, not a drill motor. Careful, the 9 year old plastic cam be brittle. Squeeze the tabs and carefully pry up.

That's my thought for the day.

 

Thanks...I will check those items when I get home from work tonight. Although, here in Florida we tend to have few issues with gunk build up - air filters stay very clean - we have sand - not dust.

No, the check engine light does not come on. I had it into the local Jag repair shop and they claimed it was a fuse, but I am skeptical (they had the car for 2.5 days....maybe they were just backed up....? I don't know.).

The funny thing is that each time after messing around with switching relays the car did start - of course - it may just be a coincidence. Everything under the hood (hoses/tubes/plastic) is in excellent condition and clean inside....but I will still check it all. Car has 87,000 miles and I have changed the oil more than regularly to help things stay clean.

When the car does start, it is like someone just threw a switch. It goes from barely running (sputtering, shake and stall) to purring like a kitten and revving up perfectly. When it's running well it never sputters, never misses, pops, or anything like that - it runs perfectly. I had a friend that had a Nissan SUV that had a similar problem and it was a relay - hence that's why I gravitated toward that. They would run their vehicle - get somewhere - go to restart it and ...won't fire. Same issue I am having. In their case it was a fuel pump relay......

Replacing all the relays related to the fuel and injectors wouldn't bother me - cheaper and less trouble than other trip to the shop.....and at least I could rule all those relays out if it happens again.

Do you know where the banks of relays that are near the firewall are located? I couldn't find those - they are shown in the book on the left and right just in front of the windshield. I think one of those relays had something to do with the throttle body and another was for the fuel injectors (don't have my book with me). Thought if I replaced 7 or 8 relays at a cost of less than $100 that would be one more thing I could rule out. Just can't find those relays......

I'll let you know what I find when I inspect everything this evening that you mentioned in your post. Thanks for your time and help.

 

There's a link to really good document (with lots of pictures) for cleaning the mass air flow sensor, throttle body, and part load breather that test point was referring to in the XK8/R forum, at the top, in the FAQ thread. The model shares the same 4.0L engine as yours, so many of the same troublespots are related. Good luck, we'll follow up after you report back.

 

Here is the relay layout. Most of the relays in the car are the same. Why not swap a few and see what happens.

Seems strange with all the sensors in this car but the fuel system doesn't have any. The only way to see fuel problems is via their affects.

Good luck!

 

Quick update....since switching the relays we have not had another episode (had 3 in 24 hours....). The last 2 days my wife has gone about 10 or 15 places with no incidents. However, we switched the fuel pump relay with the "auxiliary positive relay" - not sure what's on that circuit, but so far no other anomalies. I would imagine that eventually we would see something electrical not functioning since we still have a potentially bad relay still in the fuse box.

I did speak to a couple of NASA engineers on the problem and they said while they weren't experts on the car, that the failure mode that I was experiencing was consistent with a relay. The most common failure mode is a failure to engage - which is why once you are driving and the relay has already engaged to flow current, it is unlikely to disengage while on the road. Also - no other performance symptoms whatsoever - it's like someone "flipped a switch" (or didn't flip the switch....).

I did realize that on the Jag XJ8 electrical schematic that the Control Module Enclosure Relays are either on the left or right side of the car (not both). The schematic shows the relays on both sides, but now I realize that the schematic shows the same bank of relays on both sides....so the bank is represented as an "either/or"....mine is on the right side under the second cover that needs to be taken off with a torx screwdriver.

I ordered 4 new relays on Ebay (5.99 each plus shipping for a total of about $28). I'll replace the perceived "bad" relay and the two fuel pump relays and the throttle motor power relay and then wait and see what the future holds. If any problems pop back up - (or not) I will continue this post to ensure all knowledge (or my lack of....) is properly shared.

 

And we appreciate that!

 

~1:30 am last night I came back to my car ('01 VDP S/C) to go home (the car had been sitting for about two hours and was still hot to the touch). Car cranked, started, sputtered badly and died all in about 4 seconds. Repeated cranks yielded the same result (repeated about 10 times). Sounds very similar to Jim's problem.

Itmes of note
1. Throttle body assembly was replaced ~2 years ago with new part from dealer ($$$$$$$$$). Visual inspection last night showed some carbony kind of build up bellow the butterfly (probably should clean it out).

2. When key was in the run (not start) position a noise could be heard eminating from the throttle body. Somewhat similar to the noise my '78 Continental makes when I leave the lights on... kind of an eeeeeeeeeeeeeeeeeeee.

3. When I initially turn the key to the run position (not start) I can hear the butterfly in the throttle body clicking back and forth a few times. I'm assuming it is calibrating itself or something like that... not sure if that is normal or not.

4. I unhooked the battery for about two minutes. Hooked the battery back up and the car started immediatley.

I have half a mind to try Jim's approach of replacing some relays... I'm going to run over to autozone and see if there are any codes that it spits out (as a side note I have been have intermintient ABS pump failures... seems to be a fairly common issue eventually i'll take the unit out and get the PCBA fixed up).

 

#2 & 3 are normal, don't worry about that.

#1, unfortunate, but TBs in those model years did have some quirks

 

We haven't had a single problem since switching the fuel pump relay.

When your car wouldn't start, did it seem like the car would try to run at low rpm at first, but after each successive try that it would run less time? My guess is that since the fuel pump wasn't kicking on that the residual fuel pressure would allow the car to start at first - but then once that residual fuel is used, then there's no fuel available at all.

My wife called me at work yesterday and told me that her mirrors wouldn't move (the motors in the mirrors weren't getting power). This is probably because my "fix" was to switch the fuel pump relay with one of the accessory relays. Relays can fail intermittantly - as the contacts get carboned up over time. I was waiting to see if the old relay would act up again, and it appears that it did.

I found the relays on ebay for cheap, so I bought 4 of them. I'll replace the one that I had the original problem with and then I'll have some spares. The fuel pump relays are in the trunk fuse box on the left side.

If you simply switch the fuel pump relay with another relay from one of the accessory circuits, your car should start right up....the diagram shows 2 fuel pump relays, although my car only had one fuel pump relay.

If the relay is your problem - you will see an immediate result with a quick switch with another relay. I have no other performance issues with the car - so I did not suspect the throttle body. It was definitely an "on/off" situation....either it would run perfectly or it wouldn't run at all. Good luck.

 

I didn't notice it running less and less each time. It would barely even run and only for a few seconds. I read somewhere that I can put a fuel pressure gauge on the fuel rail... I may look in to getting one to help isolate the issue (if it acts up again). I don't see any reason not to replace the fuel pump relay so I'm going to do that.

Autozone read the codes and read a P1111. I looked this up in the manual and it is not any help it had something to do with resetting the computer...or something like that...probably a result of the battery being unplugged.

If it was still in the failed state it would be much easier to troubleshoot.

Like yours it was like a light switch fix (when plugging/ unplugging the battery) which leads me to something electrical. I'll let you know if I have any more revalations.

 

That's what I did. PepBoys had two gauge kits, cheaper of the two ($40) worked, as it came with a schrader valve adapter. Test point is located aft end of right fuel rail.

Ralph

 

Well, so much for me thinking I knew what I was doing…..yesterday the same problem came back and this was after I replaced the fuel pump, throttle body, and fuel injection relays. After several weeks of running perfectly, the car would not start yesterday (ironically, in the EXACT same spot at a gas station where it would not start before - that was weird). The car tries to start, but idles roughly and if you pump the gas you can hear it trying to suck air, but then the motor will eventually die, like its starving for gas. So, my perceived “fix” was wrong. We pushed the car in a parking spot and came back for it 2 hours later….and behold – it fired up and ran perfect.
We are going to take the car back to a father/son Jaguar repair that “fixed” it the last time. (They said it was a “fuse”…..well, the “fuse” repairs itself after cooling for two hours). We are hoping that they can look for trouble codes and perhaps that they have observed this phenomenon before.
So, the car is going into the shop today. As promised, I will keep you posted….even if it means that I have to concede that I’m not so smart as I thought…L. (PS, all this happened while I was removing the intake manifold from my daughter’s 3.4 GM V-6 – the engine model that has the gasket leak problems (coolant leaks)! All this right after working a long day…… I was not having a good day).

 

My fuse turned out to be blown as well and replacing it did not fix the problem. After significant troubleshooting I determined that both fuel pumps had failed. Just got the pumps out last night and one of the pump connectors was fried...I'm guessing leading to the fuse blowing. I'll post some pictures. Btw getting the fuel tank lines disconnected was not fun ... more to come on that later.

 

My wife called the father/son jag shop and explained the intermittent "won't start/cool, then start" phenomenon. They said not to bring it in since it's running....they want to ponder the problem and come up with some potential causes. That was not encouraging....

I've thought of things like the crank position sensor, etc., but the failure mode of a lot of components like the CPS would result in zero spark....we are getting some spark because the car does sputter at low idle for several seconds when started, then dies. If you pump the throttle you can hear the car try to pull air (you hear the "bog" sound of the air trying to go through the throttle body), but the car acts like it's starved for gas.

If you let the car sit - it will eventually start - and I mean it can act just like above one minute, and the next minute it will start normally - it's not like the car is flooded or vapor locked - like I've said before, it's like a switch going off.

I do have considered that perhaps the fuel pump is overheating (it only happens when the car has been running) and then for some reason the pump motor stops in a position that resists restarting while it is hot. The next time it happens I am going to try to pound around the gas tank figuring if the fuel pump has a motor problem - that a little vibration might help overcome it......I've tried searching the web for other cars with the same problem (not Jags) and I've found a few cases, but no definitive solution/cause was ever posted for those cases.....

 

There are some excellent posts on troubleshooting fuel pumps (just do a search). Net is you can do a quick check at the fuel rail shrader valve for fuel pressure. Also you can put your ear on the gas tank (easily accessible from the trunk) while someone puts the key into the run position. You should be able to hear the fuel pump turn on for about two seconds.obviously you will.want to do this when the car is failing. My instinct still say fuel pump especially with the blown fuse. Wouldn't be surprised if your harness is fried as well.

 

Also, try this. Before turning the ignition over, let the fuel pump run (key in position II) for an extra few seconds to bring up to proper pressure to start it. You might try also changing your fuel filter yourself for less than $10.

Anyway, here's my thoughts. If you get just enough fuel into the engine to get an idle but not enough or long enough to continue the proper combustion variables to run, then shuts down, you could be getting a slight 'cylinder wash' scenario. Those engines are not recommended to be started and ran for a short period due to that very condition. Then when you go to restart it immediately, it won't fire.

Any of that make sense?

 

I took a few moments to read this post and if you have fuel and spark that I think you have then you need to make a few other checks. In the trunk you have a high voltage fuse box near the battery. Remove the positive battery terminal and examine the box and fuses. If the box is cracked replace it and the fuses inside. If it is not cracked check the fuses, remove them if you need. One if the fuses goes to the fuse / relay box for the Engine Management Fuse Box and the 2 fuses that are stacked are used for the Starter and Generator. Think about it the starter turns and the car does not start. This fuse box is often cracked or broken when the tire is loose in the trunk or bumped when installing the tire in the trunk. You can get a oneline for your car from my page.

Now just recently I had my car stall and no start for about 30min and it started when I took the 2 plugs to the TB and moved them around. I was taking a guess when I did that but it worked. When I got to my destination I cleaned and sprayed the plugs and drove the car for another 600mi now and no problem. I should note that I did not get any codes and I have a new TB & TB gold plugs.

Please let us know how you make out…

 

Hope this helps

 

gus, any way you can make your pics any bigger? I can't even read it.