Hi there - just joined the site, and this is my first proper post. I checked the other threads and thought there are several along this theme related to pre-2005 XKRs, I couldn't find one about the 05 / 06, as in the course of this investigation I found a couple of the subtle changes the boffins at jaguar must have made in 05 (couldn't stop tinkering with it I guess)... Here goes:

05 XKR conv with 121k miles on it, rescued it from a shady looking used car lot in Mass in March with 117k miles, knowing it would need some TLC, and being an amateur mechanic (worked on a 993, cayenne S, and old jags) I figure let's have it. At purchase I took it to a jag dealership and it checked out for codes, car fax, and 27 point inspection.

I've had two issues with it so far, first I learned how to clean the air intake and throttle body... The mismatched reading between the pedal position and throttle body motor position went away after that. Got stranded and towed in NJ one freezing night in March. Ironically, just as my 05 was being pulled onto the tow truck, a silver '97-'99 XKR went screaming by, california-rolled through a stop sign without a care. My shame.

Okay, the issue at hand is that my car won't turn over, it cranks strong, battery and cabling looks recent and reads 12.2V... Drove around DC a couple of days ago, stopped and started several times, then on my way home I bought gas. My fuel range was 30 miles, so figure the tank was just into the red. I've done several long road trips in the car already and generally avoid running the tank low. So I filled the tank and headed home, parked it over night, then in the morning it wouldn't turn over at first, but after a pause, I turned the key again and she ran.

I thought it was the alternator, as I have noticed the headlights and cabin lights flickering lately, especially if I use the dimmer in any position other than 'on', for the cabin lights. I ordered a new alternator which ironically is waiting at a trusted mechanics shop in Ohio, which I planned to drive to this weekend (from DC) and also get my brakes done and fit my new Coventry Whitleys.

On the way to work I stopped to get coffee and the car started fine, then when I went to crank it at lunch she wouldn't go. By mid afternoon I'd scoured the forums on here and signed up :-)

Which brings me back to my original comment about the 05 having some subtle differences to the earlier XKR's... first I discovered the inertia switch in the drivers side fascia fuse box is actually located behind the plastic molding that also covers the bonnet release lever. (I also found a horrible bundle of wires shoved up under the dash, which I think are related to the aftermarket Sirius and iPod integration, which will be another post shortly). Secondly I found that there are two empty spots in the fuse compartment in the boot on the passenger side, where the fuel pump 1 and 2 relays are found on the earlier XKRs. There is a place where fuel pump 1 relay 'could go', but there is no receptacle or connector for the pump 2 relay. This makes me think that either the 05 XKR has the relays located elsewhere, OR the design somehow doesn't use relays. The owners manual doesn't mention it, I can't find a diagram for the 05 online (latest one I found was for the 03).

I moved the brown relay for the rear fog lights to the position for the fuel pump 1 relay, and my friend cranked the ignition while I groped the relays to see if anything was happening - I felt one initial click at the relay which makes me think that IF the relay was indeed deleted by design, then the inbound circuitry is still the same, and will still try to start the pump, even though the relay isn't used on the 05 - I'm thinking out loud here - correct me if I'm wrong, thanks. If the relay was removed by the previous owner, then maybe there is some ugly hardwiring job lurking in there somewhere, and likely the pump is dead. Anyway, speculation aside for a moment, back to the facts. So, with the relay in the spot for the fuel pump 1 relay, I could not hear any sound coming from the fuel tank that would suggest the pumps are working. Same with no relay in that position, in the condition I found it.

Before tearing out my fuel tank (it's full, by the way... love that long range tank, but not today) I thought maybe because I ran the tank low I might have sucked some sediment off the bottom of my nine year old fuel tank, and blocked the fuel filter (not sure if I have one filter or two), so I went groping around near the front of the rear drivers side wheel well to find the fuel filter. I think it is tucked up behind a heat shield near the rear muffler. It seems to be installed vertically, but I can't tell without raising the car. This leads me to the other discrepancy with my car - somewhere I read that for 03.5 onwards, the fuel rerun was deleted, so the XK8 would have just one fuel tube, and the XKR would have two. My 05 has two thicker tubes (maybe 1/4", not sure) and one thinner tube (maybe 1/8" dia.) so what does that mean?

I'm stranded in VA, in fact my car is presently parked in a multi-story parking lot that it would be impossible to get a tow truck into, so I think I'm going to have to fix the car in-situ. I'm going to look around for an indie who can bring a tool set (I'm away from home, very limited tools with me). I'm going to mention to the building maintenance folks I have to drain the fuel tank in their building... I won't begin the work until new Bosch fuel pumps arrive, and besides I don't have time for it this week, so I have time to think about the problem before I start tearing it apart.

I would like to do the AVOS SC upgrade at some point (thanks AVOS!), McLeod pipes (thanks McLeod!) and overhaul the engine, but if the ancillaries are failing in this ride I will be looking for an 03.5 XKR coupe with lower miles, rather than fight this old cat.

Thanks for reading - any ideas on the subject are appreciated! I'll post pics shortly.

-Ian

 

I wouldn't try using empty slots without very detailed in-depth info as you could easily fry something. R models have quite a few changes and they really matter. It may well be like my STR in which case it's the only model where both pumps drive fuel to the engine. Both are PWM so don't go messing unless you understand. Separate modules, too, unlike the other models.

It would be easy to turn a slightly non-working car into a nightmare with new faults.

Do you have good fuel pressure at the rail? There are threads about this but I think you're looking for 55psi or so.

Gus's site may have elec guide etc JagRepair.com - Jaguar Repair Information Resource

 

I don't know of any technical changes in the last years of the x100, so all should be the same as the 03 4.2L electrically.

To your first question, there is not a fuel pump relay in this car. There is a single turbine style pump in the tank with a PWM driver module behind the right hand side boot carpet.

The power feed to the pump driver is through a 30A fuse from the ignition main. There is a large power relay in the trunk fuse box whose coil is grounded through the inertia switch.

There are some relay sockets for accessory features but they are not related to the fuel pump.

When you turn the key on, do you hear the pump run for a few seconds?

There is not a schrader valve on the fuel rail so to check the fuel pressure you will need a code reader capable of scanning live data. You can read back the pressure sensor and it should say 55psi, give or take a little.

Would also be good to know if there are any codes, current or pending. Fuel pressure problems will get logged but have to occur in two back to back drive cycles, to set the check engine light.

 

If the car ran before, do not start randomly placing relays in spots where there was no relay. Rotating relays amongst populated positions is fine.

At 12.2v, the battery is more than suspect.

With the extra wiring, pull it down again and spread it out and leave it dangling so that you are sure that nothing is shorting.

 

Jag V8, CCFulton, and plums, thanks for your advice on this issue - really enlightening. I will definitely stop tinkering with the fuses now I know the pump has it's own controller! The tip about reading the fuel pressure is also appreciated - I was hunting for the Schraeder valve. I have a basic ODBII reader which told me I had the throttle body position sensor mismatch, which I figure was because I tried at one point to start it with my foot on the gas.

As I mentioned I was stuck in a parking garage, and I also didn't really want to have to repair the car in situ, so I was contemplating rigging a jerry can with a fuel pump and 24v battery to get me to a garage. I think the Jag didn't like this, and decided to cooperate after a few minutes to think about it. I was able to drive it to Rosenthal Jaguar of Tyson's Corner where I received a warm welcome!

The car ran well, which suggests I either have a fully blocked fuel filter, and some fuel finally came through OR more likely there is an electrical short. As I mentioned, there's some gnarly aftermarket wiring under the dash, and some thick multi-core cables go from the boot to under the bonnet, but they are interrupted with some after-market connections, and stuffed into a space under the steering column, wedged behind the little sunglasses cubby. There was also some wiring stuffed into the lower plastic cover that enclosed the trunk release lever. I pulled these panels off and let the wiring hang. Wow, what a mess. My phone was dead so I didn't take a photo, sorry, but basically there were some wires capped off, three grounds just hanging there, a free red wire, and 6 connections that were made with those push-on connectors. I gave each one a squeeze, taped the loose ones, cable-tied them, and put them back where I found them. Then the car started.

There's an aftermarket bluetooth in the car, and I suspect that it is part of the problem - I don't have the code for the bluetooth and can't find the module to reset it, so it's useless to me. bluetooth is still searching even when the car has been off for a while, so I know it is sapping the battery and needs to be found and removed. There's also an on/off switch and a rotary in the arm rest compartment - I've read elsewhere that this mod is sometimes related to controlling the antique antenna, but these switches don't seem to do anything. I want to say the pump is probably good, the filter is definitely getting changed, and the root of the problem may be somewhere in the bundle of wires under the dash.

White XKR also mentioned a slightly cheaper price for an OEM replacement pump which was very helpful - will consider it, if the pump is indeed bad. Because the pump is driven by a controller, maybe it wouldn't be a good idea to go aftermarket when replacing the pump. I wonder if anyone did a a kenne bell upgrade on a 4.2L, and I wonder if the stock XKR fuel pump delivers enough juice! All these things will be revealed in time! Thanks again for your help! (And sorry for the (sort of) double post - I'll get the hang of this)
-Ian

 

There has been one guy crazy enough to try it...

The pump can keep up, but I would recommend using a boost a pump for a little extra capacity. There is a lot of conflicting information on the internet about whether to put the BAP before or after the driver, most of it written by people who don't really understand what the pump driver is doing. The right answer is before.

The real difficulty in the 4.2 is the fuel pressure. The 4.0 guys add a high quality fuel pressure regulator and adjust the pressure up about 10psi over stock, to get extra fuel at the same injector duty cycle but that isn't an option for the single ended system.

You can hack the electronics to adjust a little bit but it's not reliable and you quickly run out of headroom because there is a small bypass regulator as part of the pump assembly in the tank that caps it at about 75psig.

You can either use water/methanol injection like I did to make up the difference at higher rpm or upsize the injectors, which would be a better way. I may still do that if I ever have reason to take the top off of the motor again.

 

There are more 4.2 XKRs running with the TS kit, but only 1 other that comes close in power to ccfulton. That one (done as 1st one), has also modified camshafts, running slightly lower boost due to that, and maybe that’s why fueling was is just about right.

Thanks for the info on the bypass regulator in the tank, that more or less also closes that route for adding more fuel pressure for 4.2 cars.

Indeed going for bigger injectors you get the best benefits, as the pump will be able to flow more fuel at lower pressure, which may open up the road for slightly lower base fuel pressure, to allow for even more boost if one would like to go further in power.

I am currently testing new 4.2 injectors (about 33% more flow than the stock 4.2 ones) and am very pleased with the results so far.

 

Since the system doesn't have a return and there is no other pressure relief, I believe the function is to prevent a pressure build up when shutting down a hot engine. It is situated after the check valve in the pump assembly and was actually the part that failed in my original fuel pump (it got stuck open).

I kept the old part for study and it has a lot of custom molded plastic parts to it, so I think any significant increase in fuel pressure will pretty quickly turn into a re-engineering of the whole pump assembly.

As Avos alluded to, even in my car the fueling is just slightly less than what is needed to be safe and it is only at above 5000rpm where the fueling can't quite keep up with the airflow. And even then, I am using a pretty small water/meth injection nozzle to correct the AFR, much less that the values recommended by the water injection companies.

 

Forgot even about the pressure after you shut off the engine, you are certainly right about that. I can also remember a post here about that very same issue where someone had a return valve leak and placed one outside the tank, and got overpressure issues.