Brief History: 2001 XK8 42K miles. Trying to restart after sitting for a year after misfire condition that I diagnosed as oil/water in back SP wells in each bank (1 on right side, 2 on left side also water on left side). Replaced camshaft cover gaskets and squirted a little Marvel Mystery oil in each cylinder before installing Spark plugs.
I siphoned as much old fuel as I could out (8 gal) and replaced with a couple of gallons of fresh - gauge on dash reads 1/4 full). Trying to start I found little to no fuel at Schraeder valve (dribbled out some after strenuous restarting) and before reading this warning against using it, was able to start for a second or two using a little starting fluid

My specific confusion : There is a page on JagRepair.com dealing with checking a 1999 XK8 fuel pump fuses and relays:

JagRepair.com - Jaguar Repair Information Resource

which states:

"If all the fuses are good swap out the relay in the fuse box and see if that fixes the problem. If not pull the relay and check voltage with the key on at position #2 you should have 12v & position #1 you will have 0v and at position #3 a constant 12v. If this checks out get ready to jump position #3 & #5..."

Well I assume "key on" refers to accessory position II (lights on dash) so when I did this I tested 0v at all positions EXCEPT #1 where I got 12v ! (Also I received 12v on fuse #3 and 0v on fuse #7 - both fuses had been pulled previously and examined visually and tested at Zero resistance.)
Can I assume my fuel pump is bad? (Did not try to jump #3 and #5 to listen to fuel pump after receiving these results on relay socket.)

 

First of all hello. Secondly check the shrader valve under the hood on the FUEL RAIL. You will see a little cap that can twist off then inside will be a valve similar to a valve stem in your tire. Take the cap off and then push down (please stand clear as you could get gas on your face) if there is nothing that comes out then it's the fuel pump inertia switch. It is located inside the drivers side panel. Open the door and slide your hand to the left of the steering wheel to take the cover off. Push down on top of the relay with a black rubbery piece on it and you should hear a click. Then try starting your car. Hope this helps.
Marc

 

joelsjag
Thanks for replying, already tried those two avenues. The Schrader valve only leaked a few drops after depressing with narrow screwriver and this only after extended starting attempts. I think it's safe to assume no pressure whatsover. Inertia switch was not tripped (but windows, door locks etc all worked anyway so I sorta knew this). The starting fluid test also more or less confirms it is a fuel problem as it did fire, so I am assuming fuel rails and injectors (at least some) are clear and I'm getting some spark.
I'm replacing fuel filter today but don't expect situation to change as it's pointing to fuel pump which I have on order from Rock Auto just in case (SPECTRA PREMIUM SP1113 - middle of the pack selection pricewise - anyone have any experience with this model?). Also hoping to get my son or someone else over here today to turn key while I listen at fuel door for fuel pump start and also feel fuel pump relay for 'Click'. Thought I might stick siphon tube down the fuel neck and listen at other end of hose as to better hear fuel pump)
So without a 'helper' I tested fuses and relays (according to instructions on jagrepair.com by Gus Glikas) but received somewhat different results regarding the voltage on the fuel pump socket and 20amp fuel pump fuse connectors as described in my OP. Which discombobulated me. Simply put, since I didn't get the voltmeter readings specified by Gus, does this imply my fuel pump is bad or something else? The next step would be to jump the fuel pump relay to see if that starts the fuel pump but I was a little leary about doing this with the voltage reading differences in case I fry something. (Electrical troubleshooting is not my forte. :-)

 

Hi DesertXK8,

Gus is referring to the relay connections, although I think he has #1 and #2 crossed according to the 2001 electrical guide.

With the ignition on (postion before the spring-loaded 'start') and the relay removed, you should see:

• connection #1 12 volts (relay feed via fuse #3 in trunk)
• connection #2 0 volts ('pump on' commanded by ECM)
• connection #3 12 volts (pump feed). Be careful here as there is only the 250Amp fuse in the 'high-power protection module' if you slip with the meter prod
• connection #5 0 volts.

You will not normally see any voltage on Fuse #7 (20A)unless the relay is energised.

You appear to be missing the pump feed to relay connection #3. It must be localised to the trunk fuse box otherwise you'd have a raft of other issues as the 12v from there feeds many things.

Recheck that connection #3 for power: if it's definitely missing you'll need to investigate the fuse box wiring further. Your fuel pump might be bad, but at the moment it's not getting power.

HTH,
Mike

 

Thank you Mike! - definitely sounds like I need to investigate further and get a hi-resolution electrical schematic before pulling fuel tank unnecessarily. To be fair Gus was addressing a 1999 XK8 scenario - possibly different from the 2001(?).
As an update I had a helper today to turn the ignition to "on" and was able to determine I could not hear the pump at the fuel inlet although the fuel pump relay in the trunk could be heard and felt to "Click" on.
I do have an orphan connector and a single bare (non-attached ) small-gauge whitegreen wire with a partial black vinyl jacket (like a shrink wrap but not tight) floating around the positive side of the battery compartment. The connector I always assumed was for the non-installed telephone (this is what I was told by dealership in Florisda where I purchased the vehicle in 2006 but I will investigate both it and the wire.
Sounds like unless I have power at #3 a jumper from #3-#5 to force pump on with key off and relay removed would be fruitless?

 

Yes the 2001 is not the same as a 1999.

Link to 2001 XK8 Fig 4.2 http://jagrepair.com/images/AutoRepa.../jagxk2001.pdf

 

Yes, you need the power to the relay pin #3 first if you're trying the jump wire approach. The relay sounds like it's working, but don't assume, though.

If you look in section 1.1 (top left) of the manual that Gus has linked for you, you'll see the high power protection module and the feed from it to the trunk fusebox. The symbol 1 enclosed in a square is where relay pin #3 ultimately connects to.

Absolutely wasn't having a pop at Gus - I should have worded that a bit more carefully. Jaguar has a habit of shuffling things around across the years to maintain a certain level of mystique.

As an aside, I did notice that the reverse parking sensors are hooked into the same fuse as the fuel pump relay (at least, in 2001 MY), so if they're working then it's a quick confirmation of fuse #3.


Good luck,
Mike

 

Mike again thanks..

"... if they're working then it's a quick confirmation of fuse #3. "

You did mean "pin #3" right?

Quick question (I havn't had a chance to look at the 2001 Electrical Guide yet):

Should I expect to see this +12 power at pin #3 on the fuel pump relay all ALL times when the key is ON (position II) or ONLY when the fuel pump is actually activated?

AS you said "You will not normally see any voltage on Fuse #7 (20A) unless the relay is energised.".

However that is probably a dumb question since without power to pin#3 how would I expect to jump pin #3 to pin #5l

Off to study the Eelctrical Guide.

 

No - sorry for the confusion - I threw this in after looking at the diagram. It initially seemed a curious link but, given the location of the reversing module, it does make sense. Fuse #3 powers the reversing module as well as the fuel pump relay, so it's a quick way of checking its integrity without delving into the trunk fusebox.

There should be power to pin #3 of the fuel pump relay at ALL times, irrespective of the key position, as it is fed directly from the high power protection module. You won't see a voltage on fuse #7 until the relay energises. That action connects pins #3 and #5 to send power to the fuel pump via fuse #7.

No, no dumb question. You have answered yourself, really:- it wouldn't work.

To recap:
1) There should always be 12 volts on pin #3 of the fuel pump relay, irrespective of the ignition key position.
2) There should also be 12 volts on pin #1 with the key in position II, i.e. before the spring-loaded 'start'.
3) Pin #2 of the relay should be at 0 volts.

If you can hear the relay click when you turn the key, then you have established that 2) and 3) are OK.

Once you have restored the 12 volts on pin #3 of the fuel pump relay, then with the relay back in place you should be able to hear the pump run for a few seconds after turning on the ignition. If so, you should be able to start & run the car.

If not, check for 12 volts on both sides of fuse #7:

No voltage either side = suspect pump relay.
Voltage on one side - suspect fuse #7.
Voltage both sides = suspect pump, but check its connector first for 12 volts present and corrosion. Also, check that the wiring between hasn't been pinched or otherwise damaged.

Hope this makes sense - it's getting late this side of the pond!

Mike

 

Question: assuming I have a power deficit at pin # 3 would not a direct jump from battery positive terminal to pin # 5 (protected by 20 amp fuse #7 ) on the fuel pump relay socket allow energising of the Fuel pump and therefore allow me to listen for this pump activation and therefore isolate the fault even further?
Also I may have neglected to mention I have swapped out the fuel pump relay for a
similar relay next to it with no change.
Best procedure to isolate power fault to Pin #3 on the fuel pump relay socket: remove fuse/relay carrier and test resistance along wire to pin #3 to upstream harness connector and beyond - yes or no?

 

Why not trace the lead to the pump plug at the tank and check voltage with the fuse and relay intact. That way you know for sure power is getting to the pump plug. On my car (1999) the plug was on the right of the tank.

 

Good news! I feel somewhat foolish and relieved at the same time. I will blame my eyesight and the fact that some cars, like some ladies, do not give up their secrets easily!
Seems my unresponsive pin #3 (unlike her sisters 1, 2 and 5 on the fuel pump relay base) was being coquettish! She was keeping my voltmeter probe at a distance. She was just far enough below the surface of the aperture in the plastic fuse/relay base and her slit was so tight the probe would not enter. In fact I had to use considerable force to connect, something I am loathe to do with regards all things (electronic).
But I conquered her and she gave me a +12v palpitation in response!

So manana the tank unrobing begins (and Gus I will check that voltage at the pump plug as you suggested when I unveil it!) but am all but certain now that the fuel pump said "adios".
I did not try the "jump pin #3 to Pin #5" tonight as it was dark and I needed to locate a suitable wire.

I wish to give my sincere thanks and approbations to Michael, Gus, and Joel for responding with their excellent technical expertise!

I am glad I found this site!

I will keep all posted here on final outcome of fuel pump replacement.

Buenas Noches!

Roger

 

LOL
That does make sense with the car standing for a long time, and there's precious little going on between the protection module feed and the relay in the fusebox.
You'll be less than surprised to learn that several members have already been through this. Do search the forum:- lots of guidance. Here's one to get you started:

https://www.jaguarforums.com/forum/x...lacement-8479/

There's a Rev. Sam video special on page 2, and a sample of GGG's humour to keep you smiling.

Good luck - you're getting there.

Mike

 

This is a link to a 2000 xk8 pump replacement. It is near the same as your 2001 but I think yours has one fuel line to the tank and the 2000 has two.

Link JagRepair.com - Jaguar Repair Information Resource

Hope this helps.

 

Update: Not a peep from that fuel pump when I did the "jump pin # 3 to pin # 5" !
New fuel pump arrived while I was in the midst of tearing a new one in my kitty's boot.
Why so many (6) freaking rubber gaskets? Made to fit many vehicles I guess.
Thanks to Mike and Gus for the pointers which I had already studiously reviewed!
Feeling more confidence as I am back in my element of "nuts and bolts".

Oh, and a question about blowing out fuel lines with compressed air - I assume when this is done that points downstream are opened for this? I.E. if I am blowing out the fuel lines from the fuel filter forward, I should undo the fittings on the fuel line somewhere in the engine compartment?
How about the fuel rails?

 

I haven't tried this, looking for comment. Can you use a tire inflater on the schrader valve to blow the fuel line back to the filter?

 

I am not sure you want to do that. It will blow into the injectors.

 

So what keeps the fuel from blowing into the injectors if they aren't firing? I don't understand, Gus.

 

Yes that is why I was asking about disconnecting the fuel line someplace in the engine compartment.

 

On my 99 XK8 I had 2 locations to remove the fuel lines to the fuel injector rails. See the attached photos.

Link http://jagrepair.com/images/IntakeMa...disconnect.jpg

Link http://jagrepair.com/images/IntakeMa...onnect%202.jpg