2001 XKR Lacking Power

[mike020150]

Can't give you a definitive answer but I suspect the reference to 'load inhibit' is probably about inhibiting electrical load under certain conditions. Mike.

[davidr]

Still no joy. I have taken the engine and gearbox ECUs out today to check the connections. I couldn't see any sign of corrosion or damaged pins but I gave them a good going over with contact cleaner anyway.
I was checking for a possible poor connection that would stop the gearbox module talking to the engine module. This was because I'm still suspecting that the car is in restricted power mode which arises if the car is in reverse or the gearbox ecu is missing in the CAN.
I started by trying to get a signal from the gearbox linear switch. There are 4 and the combination in which they are on or off tells the ecu which gear is selected. My iCarsoft just tells me that they're all at status 0 as I move the gear lever through all its positions. But, the relevant light for each gear lights up and that is a gearbox ecu function so I think it's doing what it should but perhaps my iCarsoft is not reading it.
I have disconnected the battery and put the car's positive and negative terminals together to do hard dump.
So, no further forward! This is getting frustrating!

[mike020150]

I share your frustration but probably not to the same extent. At this stage, I reckon you have two choices. Number one, give up to reduce your blood pressure and live longer. Number two, try copying this record of your investigative work in an email to David Marks and ask for his help. David is a brilliant diagnostic technician. If he hasn't come across a similar case, you will be very unlucky indeed. Mike.

[davidr]

I have made some progress I think.
I put the car on a truck and took it down to Hollygrove in Ringwood. First thing we did was plug it into their Autologic machine. There were no fault codes and the readings from the various sensors looked sensible.
But we could not read the Transamission Control Module which supported my theory that it wasn't present in the CAN and so was putting the car into restricted power mode.
So we found another and fitted it. The replacement TCM was visible to Autologic so time for a test drive. The car went gently up through the gears and I thought we'd cracked it but then the misfiring started again. So it was better but not fixed.
We then did loads of tests looking at individual sensors, throttle body etc but found no issues.
What we did notice was that the car would pull away best when first started but would then fade but still no fault codes. Stopping and starting again would repeat the same pattern although it wouldn't always start again first time.
This was starting to feel like a fuel issue.
Next step was to put the fuel pressure gauge on again. We were hoping to be able to see what was happening to the pressure as the car started to die and eventually stall.
With the Autologic still plugged in showing the state of the fuel pump relays (activated or not activated) we set off down the lane again. It would pull away at first and then fluff and start to stall. At this point the fuel pressure was failing although pump 1 relay was still activated until the pressure all bled away and the engine stalled.
It may sound daft but we were quite pleased by that! We were on to something!
Turning the ignition on didn't always start the fuel pump even though the ECM was energising the pump relay and hence the unreliable restarting.
Next move was to examine the relays. We tested the relay for the rear fog lamps and it was working so that became our candidate for swapping over with the pump 1 relay. Sadly, didn't make a difference.
I mentioned earlier in this thread that the fuel gauge is showing empty despite the car having probably a quarter tank of fuel. A neat feature of the Autologic is that you can send a signal to each of the gauges to check them out. When we sent a signal for a 1/2 tank and then a 3/4 tank the needle moved appropriately.
So it would appear that the sender is duff. The sender sits inside the tank with the pumps and uses the same wiring. Could we have a dodgy earth?
So to sum up, we have a fuel delivery issue which is possibly a faulty connection bearing in mind that both pumps have been renewed.
The tank probably needs to come out again to see why so I've left it with Hollygrove to fix.
Here's hoping for good news in the week!

[Astromorg]

I like it when logic beats guessing/throwing money at it!!)

[J44EAG]

This is certainly a very obtuse problem, David.

We have all (almost) been running a V8 for years and I can`t recall any of us having ever come across a similar issue. It is certainly a rare one. Keep at it, my friend. It will be great to get a definite answer to this irksome issue.

Mike K

[davidr]

Thanks both for your encouragement. Like all problems there is always a reason and a methodical approach to solving it will get there in the end.
I have been guilty of a certain amount of throwing parts at it but it's been at no cost as I had access to a crashed XJR that I could try various parts from such as throttle body, MAF sensor etc.
I'm not sure I've solved this issue but I do feel I'm on the right track. We just need to find why we are losing fuel pressure.
Of course, I've already established that my problems have multiple causes so what's to say there isn't another one yet?

[mike020150]

Great stuff! We just need the final chapter to this book. Mike.

[davidr]

So we had a little look in the tank and were horrified with what we saw! Bear in mind when looking at the pictures below that we've already had this tank out a few years ago and put new pumps in. All was clean and fresh when we put it back.
The cause of this has got to be put down to ethanol content in modern fuels. Ethanol attracts water from the moisture in the air in the tank which has destroyed mine!
If I am going to leave the car for any period in the future it will be with a full tank and some fuel stabiliser - leaving it with little fuel and so plenty of air space has been fatal.
Now we're looking for a replacement tank, sender and pumps!

Looking inside the tank there's a horrifying amount of rust

This is the lower pan where the pumps pick up

These pumps were new a couple of years ago and have hardly been used

Small wonder this sender wasn't working

[J44EAG]

Well done, David.

This issue has certain likenesses to the diesel bug bacterial growth experienced in marine situations. That was something I used to regularly see in marine fuel tanks, lines, pumps and injectors. In such a situation, any water in a marine tank would lay at the bottom of the tank and the diesel fuel would lay on top of the water. A warm, wet environment would propagate on the interface between the water and the fuel. Bacterial growth would then form on the interface and given time, the growth would die leaving hard, black husks about the size of a flea on the fuel tank floor. The volume of husks laying on the tank floor could often fill a builders bucket. The skipper of the boat would fire up the engines and put to sea. The rocking and banging around of the boat would loosen the husk deposits from the tank floor and suspend them in the fuel. Fuel drawn from a tank would be sucked through fuel filters (if fitted) by the fuel pump which would eventually block the fuel pump and or the filters. The engine would come to an abrupt stop usually at a dangerous moment in a congested harbour with large commercial vessels bearing down on the unfortunately affected yacht and its crew. Shouts of panic would be heard miles away. Call out the lifeboat....

Cleaning out a tank, fuel lines, pumps and injectors could be a foul job. If the tank could be reasonably well cleaned, we would sterilize with either bleach or methanol. We would find the type of corrosion and growth similar to that as shown in Davids post above. It was often quicker and less costly to fit a new fuel tank, fuel lines and filters and at the same time send injectors off for overhaul. We soon learned to use water dryer solution and a diesel bug anti-biotic when ever the fuel tank was filled. The anti-biotic would be changed for an alternative product every three or four months to avoid any further growth becoming immune to any one brand of chemical anti-biotic.

I agree fully with the suggestion to replace all contaminated components with new and to use fuel dryer additive regularly. I believe there is also a petrol anti-biotic which is also easily available. Halfords stock a good range of additives as do marine chandlers. I also agree that your fuel tank should be left full if you lay up your car for more than about three months. Regular sample dipping of fuel is also a good idea. If possible, the fitting of a Curtis valve in the bottom of the tank is always a good idea. This permits fuel to be dropped from the lowest point in the tank to ensure that water can easily be drained off that helping to ensure the scenario described above does not repeat itself.

Further information may be gleaned from me upon the purchase of a lunch and a couple of gallons of beer in a pub just off the M25, J11.

Mike

Glad you found the problem, David.

[davidr]

Thanks Mike. A pie and a pint is long overdue!
I'm trying not to get too far ahead of myself. We have certainly found a problem but time will tell if that Is the only remaining one. I'm keeping in mind that we've already fixed one problem that was contributing to our issues ( the Transmission Control Module being absent in the CAN network so putting the engine in restricted power mode) so what's to say there aren't others waiting for us?

[mike020150]

I think I can hear a tune playing in the distance. It sounds like, '...keep right on to the end of the road...' posting.php?mode=reply&f=64&t=14483&sid ... b04a29736f# Mike.

[RMA37]

Thanks David for sharing those photos, looks scary!

It's amazing what you can learn from the forum! I usually leave my tank full, but the car is never left for more than a month, and up to now I've used 95 octane which I've just discovered has up to 5% Ethanol in it (by law apparently). Premium fuel is Ethanol free, so is that the way to go? We seem to have regular petrol issues in the UK, leaded/unleaded; sulphur/no sulphur and now Ethanol/no Ethanol.

Your car is newer than my 1997 XK8, do you know if the fuel tank and pump arrangement is the same for all these models? The components seem to be under engineered as even condensation can build up in a partially filled tank, which is why we leave aircraft with full tanks, even then they are checked for water content before flight. I would have expected Jaguar to be aware of this problem and fitted components which would have resisted corrosion for a bit longer than 2 year's, given the showroom price of the car in excess of 60K! British car industry??

I hope you have now solved your problem. Good luck

Rodney

[davidr]

There are different arrangements of the fuel tank, pump(s) and level senders for the different years. Variations boil down to the type of tank (vapour recovery), the number of pumps (the 4.0 XKR models have 2) and earlier cars have the sender mounted on the side of the tank instead of inside like mine.
The issue with ethanol is that it absorbs water and will break down if stored for any time. There are fuel stabilisers additives that prevent that.

[J44EAG]

This is the type of product that I used to use when in the marine maintenance side of the industry.https://www.googleadservices.com/pagead ... CGc&adurl=

This is the Curtiss valve I spoke of. This is screwed into the bottom of the tank and before flight the pilot would crawl under the aircraft with a glass jar, push the valve cross bar upwards and full would drop out of the valve into the jar. 110LL (Low Lead fuel) was stained blue and was very distinctive and easily noticed. With an inch or so of fuel in the jar, given a few seconds, any water in the fuel would collect having separated from the fuel itself. The method made acertaining if there was any water in the fuel, a doddle.https://www.google.com/imgres?imgurl=ht ... mrc&uact=8

I wonder if such a valve might be a good thing in your tank bottom, David. Google to find a supplier. They are not expensive. You would though have to be able to set the valve at the lowest point in the tank and have enough metal available to drill and tap for the correct thread. A bit of welding would probably be required.

Mike K