Hi all, it's been awhile!

My 2002 XKR (convertible) which I saved from the scrapyard, and has been running quite well, suddenly began intermittently stalling after start for no apparent reason.

Sometimes it will start and run fine (for hours if I continue driving) but sometimes it will start fine but stall after 1-2 seconds. It runs great for a second, then stumbles and dies. It definitely feels like fuel cut-off, but I have been unable to confirm this with a pressure gauge yet.

Again, this is intermittent, so it doesn't seem likely to be a mechanical pump failure (I just replaced both pumps last summer, also.)

Yesterday I managed to fit a pigtail onto the fuel rail Schrader valve, but of course, this became a day which the car refused to exhibit the problem.

Vehicle detail:

- 2002 XKR supercharged 4.0L
- Later engine model with the proper timing chain tensioners
- Runs quite smoothly (when not exhibiting this issue)
- 95,000 miles
- Relatively new battery (last summer)
- Drives great, plenty of power
- Both fuel pumps replaced last summer

Problem detail:

- Starts fine (initial rush of fuel)
- Stumbles and dies after anywhere from 1-3 seconds (definitely feels like fuel starvation)
- This can happen whether hot or cold (happened in the AM with a cold engine, also happened after a day drive, after filling the tank at a station)
- There appear to be no DTC's triggering when this happens

Things I have done:

- Checked fuel pump relays for #1 and #2 (both are good)
- Opened the ECU and checked for any damaged / leaky capacitors (no damage found, looks to be in mint condition - though I realize there could still be bad caps, I'd like to further isolate the issue before jumping to this conclusion)
- Found, and then plastic-welded, numerous cracks in the air intake hose (it's not ideal, but functional) I do not think this leak would have been bad enough to cause such a hard stall, anyway.
- Checked DTC's, there are none (I cleared a random misfire code which hasn't come back)
- Attached a fuel pressure gauge, but have yet to recreate the issue (I'll try again later this evening.)

My theory tells me that the computer is deciding to cut off fuel for some reason, perhaps a bad signal from the MAF? But before going further, I want to confirm this by checking voltage at the pump connector above the tank, I expect I will find that pump #1 is priming the system, but pump #2 is failing to carry the fuel pressure after startup. A drop in fuel pressure plus no voltage to the pumps would confirm this, I believe.

I'll post findings once I am able to recreate the issue, hopefully this evening, and get more data.

As always, I appreciate any / all input!

 

I would replace the fuel filter if you have not already done so....

 

Yes, apologies, I failed to mention that. Here's all the work I did last summer:

- Front shocks (with the expensive Bilstein CATS-compatible ones)
- Brakes all around (turned the rotors too)
- Fuel pumps and fuel filter
- Dropped the rear axle assy and replaced the rear differential
- Driver's side mirror & door card

 

I have a hard time remembering that replacing a part does not mean that it will last as long as I think or hope.
Also, when you replaced the fuel pump, did the fuel pickup strainer get replaced? And how are the electrical connections in there? That fuel pressure gauge will tell you much. If you have a gauge that you can read in the car while driving, that is the best. On my 55 chevy pickup with EFI, I have both a mechanical gauge that is permanently mounted in the engine compartment (for setting the adjustable fuel pressure regulator) and an electrical gauge in the dash that tells me if there's a loss of pressure while driving.
I don't think that it would be related, (even though its at the fuel tank) but the evap system on my 2002 has had to be replaced, but that gave codes that pointed to it.

 

And one more thought.
Have you done a smoke test on the intake to look for leaks?

 

I know you mentioned that your battery is relatively new….. but, have you tried keeping it on a battery tender whenever the car is not used overnight or longer ?

sounds like a long shot I know. But the battery tender technique has banished all types of gremlins from my 2002 XKR that were plaguing me. (and my battery was new also & charging system fully functional too).


worth a try with a CTEK or NOCO Genesis, etc. They are miracle makers.

Z

 

Hi there, did some digging and found this, hope its useful.

From the Manual;
The ECM will disable the fuel injectors, ignition coils, fuel pump drive and starter if any of the following conditions apply:

-A theft signal has been received from the IC, i.e. the key code has not been received/code does not match.
-A challenge code has been transmitted to the IC but no response code has been received.
-A challenge code has been transmitted to the IC and an incorrect response received.

If any of the above cases apply, the ECM will log DTC P1260. This DTC is further defined by sub-codes. The sub codes are accessed through freeze frame data. Additionally the IC will log DTCs if the failure was a result of the key transponder exchange.

System Diagnostics; Engine Fails To Crank; The most regular occurrence for failing to crank is due to the Park & Neutral start switches, that is, gearshift not in Park or Neutral. The starter relay configuration is as follows: low side of relay coil - switched directly from ECM (if conditions correct) high side of relay coil - direct from transmission P/N position.
-Other likely causes maybe that the CAN / SCP network is malfunctioning, i.e., the CAN circuit is open/short. This would mean that the IC/ECM or IC/BPM would be unable to communicate resulting in no authentication being performed to enable the ECM.
-Transponder key may not be programmed, or the KTM has not been taken out of build mode etc.

Engine Cranks but will not Start
If the Engine is cranking it means that the ECM is enabled with respect to the immobilizer function. If the immobilizer had failed validation the ECM would not engage the starter. This could beconfirmed by reading DTC from the IC and ECM.
In this case, the fuel pump circuit should be verified. A fuel pump module, which is controlled by the ECM, supplies the fuel pump.

-In all cases of suspected immobilizer non-start issues, the most logical failure modes should be eliminated first.

-Check all relevant supplies and grounds to the KTM, BPM, IC and ECM, check that the starter relay has a permanent 12V supply, check that the relay has a 12V supply and ground across the coil while the ignition is in the crank position.

/E

 

Thanks for all the suggestions, folks.

There is no DTC P1260, there is P1316, P1000 (I recently cleared the codes,) P0300, P0305, P0307, P0308.

When it's running, it runs fairly smoothly and has plenty of power. When it exhibits this condition, it will keep stalling out for maybe 20-30 starts, and then it will finally start and continue running. After that it drives fine.

I have read somewhere that it gives fuel pressure thru OBD, but the reader I have does not display fuel pressure as a value. Is there a Jag-specific reader that shows this?

Today it drove fine, but on the way back from the grocery store, it went to failsafe engine mode for some unknown reason. That's when I pulled the codes above.

I would like to catch this condition when I can attach a fuel pressure tester. I tried to leave a pigtail connected, but it's not a good idea to leave that connected long-term. So I'm hoping it will exhibit the problem some day on a cold start-up, so I can get in there and attach a tester to get a reading. I expect I'll find it is dropping pressure and the fuel pumps are not getting any power when this is happening.

I considered swapping relays when it occurs to see if that could be it, but it seems if a relay was failing, it would just not work at all. Can the relays in the boot be swapped around freely? Or are there specific types for each port?

Also, does anyone with some decent electrical knowledge know if it would be safe to attach 12v bulbs and splice into the fuel pump wiring to have a visual in the car, that the pumps are working? I considered attaching bulbs to both pump positive wires (running to ground on the chassis) to observe normal function, and see if it is in fact simply not activating pump #2 in this case when it stalls out. But I don't know if this would put too much strain on the circuitry.

 

Misfires being reported, all on one bank (B):




I've included P1313 as the P1316 refers to it.

Could you try a $0 test? - switch the coil for B2 (6) across to its opposite on Bank A and see what happens. I'm wondering if this coil is affecting the others on the bank. If it is, then the codes should change.

Or swop out coil B2 if you have a spare.

edit: Sorry, ignore that. What I was thinking of would affect two cylinders on each bank, not all on one.

 

If I am understanding this right, you suggest moving the second coil (from front-to-back) of left (U.S. driver's side) of engine to right side, same slot. Is the theory that this coil is robbing power from the ignition module and starving the others?

When time allows I'll get in and try this swap. I might swap both #'s 2 and 3 to see also, if it moves zero, one, or three codes to the other side. P0307 seems to trigger earliest.

Great suggestion! Thank you!

 

The 4.0 cars don't have fuel pressure readable over ODB - the later 4.2 cars do - so you will have to use a mechanical gauge.

If you suspect the relays, I would buy new ones and fit them - you will then have used spares to keep in the boot, but yes you can swap the same type of relays around.

If you want to add a telltale light, I would use 12V LEDs so there would be no additional load on the circuit. This would at least give you an indication that there is power, although it wouldn't prove the pumps are running.

 

Right, the test is really that they remain dark, confirming my suspicion that (1) It is in fact a fuel problem, and (2) the ECU or relays are at fault, in one relatively simple test. I will order the replacement relays as a matter of course as you suggest, but I also will temporarily set up these LEDs.

This is perhaps a silly question, but would you run them in parallel, or series? My thought is that I would tap the positive and run them to ground in parallel, unless LEDs are unique in that they will not add any measurable resistance in series with the pump... I have to admit my basic electrical knowledge is lacking in this area...

 

You have to put the LEDs in parallel, they won't pass enough current in series - this is the easiest test you can do.

You can use your multimeter in amps range in series to check the current draw when the pumps are running. Another test is to wire a suitable 12v bulb instead of the pump - this will show if you have 12v, ground and enough current flowing under load.

 

This is something similar I did to test the CATS suspension - Posi-taps to connect the wires which I ran back to a 12V LED on the dashboard.

 

The car Wizard on Youtube uses relay "tools" to check circuits. They're relays that have switches on them to power the circuits. I don't have any & never tried them, but plan to get some. He has links to them if you go to one of his videos.

 

I remember him - he was the guy who burned Hoovies Ferrari down by not changing the fuel line, lol.

 

Apologies for sending you off on the wrong track. There's no harm swopping a known-working coil into one of the positions where you're getting a misfire code. Sympathise, as intermittents like this are likely electrical and can be a royal PITA to track down.

Follow dibbit's suggestions for now as they're straightforward and should eliminate or confirm a fuelling issue.

 

I've got the fuel pump relays, posi-taps, and LEDs on order. Hoping all should arrive for the week-end, more likely Monday.

I've got the wiring schematics from jagrepair.com in hand, ready to go, will advise once I get into all this further.

Thanks everyone!

EDIT: Just in case someone else finds themselves in this same situation, the pertinent snips from the schematics here:

 

I would not use LEDs for this check, as 12v LEDs will still light at a lower voltage without dimming much and would only be useful as an indicator for a complete loss of power.
Better to use a low wattage 12v bulb, say 3W dashboard type bulb, as that will give a much better indication of any intermittant resistance causing a voltage drop with corresponding reduced pump pressure/flow output.

 

Have you tried to replace the flywheel/crank sensor.. can cause all sorts of missbehaviours.. should be an easy fix in order to rule it out.
It sits 6 o´clock right under the engine.. maybe an oily contact?

/E