After a few months of downtime sitting in the garage, I finally got around to swapping out the two bad fuel pumps in my XJR. It wound up not being too bad of a job (although admittedly I feel like there's still a hint of gasoline smell in the trunk - I think it's possible one of the hoses I reattached isn't airtight).

Anyway, car started up and ran like a champ. Everything was hunky dory until a few days later when I took it on a little 80 mile shakedown.

Restricted performance kicked in at 40 miles out.

It is happening intermittently. When it kicks in, the idle goes rather low (500-600) and the car runs shakily. Once I turn off the car and give it a few minutes, I can fire it back up and it'll run like a dream for awhile, but at some random point it will start acting up again.

A laundry list of codes are popping as a result, but it looks like the important ones might be related to a fault in coil 3 and 6...

So, I guess the big question is - did two of my coils really just spontaneously fail as soon as I got the car running again? It seems unlikely to me, and the fact that the problem is intermittent is even more frustrating. In the past when I've had a coil go out on a car, it's usually broken until I fix the coil...

Is there some other possible explanation or something I should test before I start yanking coils?

I've thrown a battery charger on the vehicle for today in hopes that perhaps this is a symptom of a low battery (it had sat for several months without the tender attached, so the battery is probably a bit low even after my shakedown drive). Any other steps I should be considering here?

Also, should I be concerned about the faint gasoline scent in the trunk? Some gasoline obviously was splashed around when I yanked the fuel pumps (despite my attempts to empty the tank), but I figured the scent would dissipate by now... Thoughts on where the scent might be coming from assuming it's still escaping the tank?

 

Did you replace the fuel filter??
Maybe a slightly 'cloggy' filter is running it lean or an injector has a poor spray pattern??

Make sure all the tank vents are attached correctly.

bob

 

I would make sure you don't have a gas leak. We had a member on the X100 site have a fuel pump replaced in his car by a shop. He filled it up with gas and just as he got home the car caught fire and was a total loss. So if it were me I'd make sure you don't have a leak and if you do take care of it first.

 

Yeah, that was my initial worry, but I've inspected it and I don't see any leaks or evidence of leaking.

It's certainly not dripping gasoline into the trunk or out onto the ground. The scent of gasoline is extremely faint, and as I said, a bit of gasoline did get spilled during the process which makes me think it might just be residual... but it still concerns me a bit.

 

I did the fuel filter at the same time I did the fuel pumps.

I've checked the tank vents as best I can with it in-situ, but to do any more would require yanking the tank again... All the hoses etc are attached correctly as far as I can tell - they were certainly seated properly when I put it together and looking/feeling around they are attached.

 

Well, the battery top-up did nothing. Started the car and it ran absolutely perfectly for twenty miles, then it kicked back into restricted performance for the whole drive back. Stopping and restarting won't turn off restricted performance either. The car has to sit awhile to go back to running properly.

while in restricted performance it feels awful. Engine is rumbling and idling low and feels like a cylinder isn't firing right.

Guess im going to replace a few coils. Any other ideas?

 

Check out this post. Read motorcarman's post
Could this be a possibility?

https://www.jaguarforums.com/forum/x...ssible-175367/

 

Xjarmageden,
The very same thing happened to me, Lots of faults then nothing for days, then faults again then ok then eventually faults all the time.
My problem happened to be the throttle body as one of the sensors had gone bad and I had to replace the whole thing as you can not just buy the sensors on there own.
I do remember reading that sensors from another car work in it but I am sorry to say that I can not recall where I saw this although I do think it is on this sight.
Cheers,
Knobby.

 

Since the only major work performed was the replacement of the fuel pumps I think your problem has to be with them.
You didn't note what kind of pumps you installed.
Probably the best way to make the determination would be to have an OBD scanner that can give you REAL TIME readings. You need to monitor fuel pressure and fuel trims.
I think one or both of your pumps are failing after you drive a short time.
You might try removing the fuse or relay for pump one to force the ECM to run on pump two and see if you still have the problem.

 

Thanks for this. I'll crawl under there and see if maybe somehow the pipe is bent. That seems unlikely, but there's always a chance.

 

I swapped them for a couple of Densos. Did plenty of research to make sure I was getting the right ones.

I'll give the relay trick a shot and see if that helps... Got a suggestion for an OBD scanner to buy that will give me the readings I need?

 

On a sidenote though... If it was the fuel pumps why can I walk out and start the car and have it run FLAWLESSLY right now? It seems so weird that it starts having issues after a 20+ mile drive...

 

Is the fuel tank developing a vacuum maybe? When it starts running badly take the gas cap off.

 

How did you access the pumps???
Cut a hole in the rear parcel shelf??
Remove the tank into the boot area??

If the tank was pulled into the boot area, did you disconnect the lines from the bottom of the tank or just pull and bend/damage the lines??

bob

 

A lot of folks like the ELM 327 with the Torque app. But take a look at the stickies and you will find a lot of info about code readers choices. Myself I use one from OBDCOM only because I prefer a PC based scanner.

The fuel pumps receive all of their cooling from being submerged. If one of them is breaking down it wouldn't show up until after the pump has warmed up.

 

I know I always say this when someone has Restricted Performance issues, but it sounds like the typical Throttle Position Sensor issue.

You really need to check the codes though.

Coil packs tend to be quite consistent once they fail, and show codes, as do other misfires. Fuel starvation won't throw any codes, but is pretty uncommon, especially if they've been recently replaced.
The TPS may not throw a proper code for quite a while, which can make it hard to diagnose. I would definitely recommend the ASI rebuild if you do suspect it's the TPS. Plus with a lifetime warranty, even if it's not the cause this time, it will stop it being the cause in the future

 

I did it the usual way: Drained it as best I could, disconnected fuel lines (which was a bitch), unbolted everything in the trunk, pulled it into the trunk and out of the vehicle (spilling a bit of gas into the trunk in the process), emptied it the rest of the way, then swapped pumps (and the melted connectors) and reversed the process. I'm confident that I completed that job correctly.

I did consider cutting a hole in the parcel shelf, and if I did it again, I think that's exactly how I'd accomplish the task next time round. Removal of the tank was a lot more work than I anticipated and I wish I'd have just cut the damn hole.

I didn't notice any bent/damaged fuel lines when I bolted everything back together, but the tank was a bit difficult to get back into place and it's at least possible that I tweaked something in the process. I'll have to crawl under there and look later today. Even if the line was bent though, I'm still puzzled as to how that could lead to this problem. When I start the car, it runs and idles perfectly and it drives properly (all the power I expect when I give it gas is there - it accelerates just like it's supposed to).

If it were a bent line or some problem with fuel delivery, wouldn't that cause problems from the instant I start the car? It seems unlikely that would cause cylinders 3 and 6 to misfire/pop a restricted performance code 20 miles into a perfect drive.

 

Let's stop guessing. If you have or get a fuel pressure gague with a long enough hose so you can put ot so you can see the gague while you drive. Monitor the pressure as you drive. If the pressure drops as you drive or if it drops to zero when it dies you have a fuel problem. If the pressure stays up it's probably electrical.

 

Sounds like time to get a fuel pressure gauge with a long hose.

I've never actually checked fuel pressure. I'll have to look up the process.

 

Well, after giving it a once-over I determined everything was fine except the #3 coil. Replaced the coil and it's running fantastic again.

Sometimes the simplest answer really is the correct one. No idea why the original coil was failing after 20+ miles, but there you have it. The car is running flawless.

Of course, that doesn't mean it's completely trouble free... Now, for no reason whatsoever, my fuel gauge seems to be working intermittently. Sometimes when I fire it up it'll work, sometimes it won't, sometimes it'll stop working at a random point along a drive. Seems like a loose connection of some kind...

Somebody tell me I'm not going to have to get into the damn tank again to fix that... lol