I'm having a problem which I'm pretty sure is a failing fuel pump; at least the symptoms seem to indicate that. It initially started out with PO171 and PO174 codes which refer to lean conditions on both banks. Those codes went away after a few driving cycles. I also noticed some surging under hard acceleration. The next symptom was hesitation and "popping back" in the intake manifold upon hard acceleration, but no new codes. And, when I turned on the ignition with the engine cold, the fuel pump ran for at least 15-20 seconds before stopping, and seemed to laboring. Finally, I'm getting zero readings on both long and short-term fuel trims; other parameters seem to read fine. All of the symptoms scream failing fuel pump, to my mind (or, if I'm lucky, a clogged fuel filter).

I'm on my way out to purchase a fuel injection tester at Harbor Freight to try to finalize the diagnosis. Any thoughts? And, if it is a bad fuel pump, any suggestions on where to purchase a replacement?

Thanks,

 

The fuel filter is supposed to be replaced every 30K miles. A clogged filter will shorten the pump life.

bob

 

Check the air flow meter. If in doubt, do a thorough cleaning with a dedicated spray (CRC Air Flow Cleaner). Hit every nook and cranny. When you think it is clean, do the cleaning again. Let it air dry between cleaning. I would not use any brush, or towel, or anything, just the spray. When putting it back, make sure the o-ring is not getting pinched. It is probably a 10 min job.

You can never go wrong with a new fuel filter, especially is the history is unknown. A bit of a pain to reach in the driver side rear wheel well, but cheap to buy.

On my later 2003, the fuel pressure is available as a data point over OBDII (ELM327/Torque Pro). I am not sure it is available on the earlier cars, but it is worth a try. Mine reads a pretty constant 55 psi.

Best of luck, keep us posted.

 

The fuel pressure is completely different for the 4.2 'returnless-system'.
The 4.0 uses a mechanical fuel pressure regulator and return line.

bob

 

Clean the MAF, that's easy and cheap and just good to do over time anyway, especially with the fuel mix related issue you have.

Test the fuel pressure at the schrader valve at the fuel rail at various times (primed, start, idle, revs) and see there.

I recommend changing the fuel filter either way. If it hasn't been done in the last 30k miles, it's pretty darn simple and under $10. Good to help prolong life of the pumps per motorcarman. Not a Jaguar specific thing but a clogged filter will always require more effort to push fuel through than a non-clogged one.

This is not Jaguar specific but I always recommend keeping a decent amount of fuel in any car, one reason is that inside the tank pumps use the fuel as coolant, as well as when the tank is low they have more opportunity to suck up crap. The socks on the pumps will help to prevent them from getting into the pump, but require more work on the pumps part to suck fuel when they are filtering crap. Plus fuel tanks full of gas don't rust out like a partial tank since the gas will prevent evap and condensation to have water sit and rust crap out. It won't prevent everything, but basically more gas in the tank is less problems.

BTW - I used 2 of these in my XKR (almost 6 years ago, so the part's solid), one of them is enough for your XK8:

Pump: http://www.rockauto.com/en/moreinfo....sn=377&jsn=377
Filter: http://www.rockauto.com/en/moreinfo....440759&jsn=504
Strainer: http://www.rockauto.com/en/moreinfo....440759&jsn=523

 

UPDATE: Wow, thanks to all. The fuel filter was changed 5,000 miles ago, so unless a bunch of crap in the tank broke loose and clogged the pickup screen, it's probably okay; going to change it anyway. Engine still runs smoothly at all rpm's. Picked up a second trouble code: P1647, if that's relevant.

Tested the fuel pump pressure with the car stationary, and got the following readings:

When ignition first turned on: 35 psi
Engine running at idle: 32 psi
Quick throttle opening: 35 psi
After warmed up and shut off: 40 psi

Still have no fuel trim readings. I'm going to clean the MAF next; good suggestion.

Thanks to all,

 

Okay, before I look any dumber that I am, I checked the P1647 code which is for one of the O2 sensors; very likely the problem. Would that prevent any readings for the fuel trims on either bank? The sensors are relatively cheap (on the Jaguar planet, anyway); are they a huge PIA to change?

Again, thanks for bearing with me on this.

 

That's an O2 sensor code for the upstream on the Left Hand (LHD driver's side) O2 sensor, which should be under the coolant tank. You pull the cat off the car to do it.

I recommend just doing at least both on that side if you do end up needing to do O2 sensors as it's basically just $50 more to do the lower one and all the hard work is already done. Difficulty is basically determined by how rusty the exhaust is, and whether you have a torch to heat things up. I had to heat up things at the flange to from the cat to pipe (not headers/collector end, the other end downstream) to get the nuts off the studs. I used my best snap on bits and extensions to get the 3 nuts off on the collector to cat flange. I don't recall entirely, but I think access was rough and I used 1/4" drive stuff (hence the high quality tools)? I recall that all in I spent maybe 3 hours on the job. Not too bad really. I don't have a lift and exhaust stuff can do from no big deal to heating and beating quickly lol.

 

There are lots of posts on this code. Happens a lot.

Before going to the sensor, check the wiring diagram. These sensor heaters are powered through a relay and a fuse. Fuses are easy to check, but for the relay, you can swap the driver side with the passenger side and see if you get the companion code for the other side (P1646?). If so, then change just the relay. Technically, you can check the resistance of the sensor heater. All 4 plugs are behind the throttle body, fairly high up on top of the transmission.

For the sensor, double check you are getting the right one. I went with Denso. The key is that the upstream sensors are wideband, not narrow band like in the 90's. The downstream sensors are the old narrow band type. Wideband sensors are a bit more expensive (not a lot). eBay is a good source.

For access, you should be able to see it from the top. It should be fairly high on the catalytic converter. It was reachable with a socket on my '03, but yours might be different.

Best of luck, keep us posted.

 

Can anyone tell me what the normal xk8 fuel pressure range should be? I believe that it's 42 psi, but don't know how sensitive a number that is with regard to performance. My readings are as follows:

When ignition first turned on: 35 psi
Engine running at idle: 32 psi
Quick throttle opening: 35 psi
After warmed up and shut off: 40 psi

Planning to change the fuel filter in any case; just hoping that it's not a fuel pump issue.

Thanks,

 

The fuel pressure that counts is measured relative to the intake manifold, not atmospheric pressure. Fuel pressure regulators typically have a vacuum line to the intake manifold for this purpose. If you want to test this, you can (briefly) remove that vacuum line (and plug the hole) and make another reading of the fuel pressure. Should get you closer to 42 (ultimate number and all that).

In my experience, bad fuel pumps just quit. Although I cannot confirm these exact numbers, my sense if that your fuel pump is just fine.

 

that fuel pressure is good.

Gus
www.jagrepair.com

 

Have you added any fuelling additives to your car? If not I would recommend doing that. As for the O2 sensor it can be changed from the top just not easy.

Gus
www.jagrepair.com

 

Thanks everyone. I'm going to check out the fuse and relay to that O2 sensor to see if I get lucky. As far as the sensor removal being "not easy"; why would it be any different than most of the other repairs to an XK8?

 

Was able to find and swap the relays; no difference. Been trying to find the fuse for the upper driver side O2 sensor. Gus's site has a complete electrical component breakdown (and I do mean complete!) that lists all of the fuses, but I've not been able to decipher the nomenclature to identify the fuse by number. If anyone has access to a dumbed-down list of fuses, I would really appreciate it. This is kind of a "Hail Mary" before I suck it up and pull the sensor.

Thanks again to all!

 

The user-friendly list of fuses is in the Owner/Driver's manual/handbook.

Once you are past this, can you re-post the current status with all the current error codes, and if you can read the fuel trims?

Also, spend a few minutes and do a good cleaning of the air flow meter. It is near the air box, on the big pipe to the throttle body, and held by 2 screws.

 

Thanks, on my to-do list. I'm pretty sure the fuel trim issue is related to the O2 sensor, but at a loss to explain why I get no reading on either bank. It looks like I'll have to replace the sensor and see if I get my fuel trim readings back again.

 

Sensors aren't fused separately. One relay heats them all. Fuses to check as per picture. But if fuse has gone no sensors will work.

 

Check your PM

 

Check ur vin number is correct on the diagram. Is ur car NA?

Fuse 1 engine management fuse box.
Fuse 14 " " " ".