Greetings
I have a 1995 xj6 with 90,000 miles. It has been a great car for me for 2 years and suddenly it would just quit running randomly. Typically I would get it towed home and the tow drivers would ask why i had it towed since they were able to drive it onto the flat bed. This caused problems since one cannot diagnose a problem that does not exist.
Searching this site I began to suspect the fuel pump (because of age mainly) So I replaced it and the fuel filter. The car started up fine and purred in the driveway for 20 minutes. This means nothing because it started and ran fine before the surgery. So I take it for a drive and it quits about 1 mile from home. Tow it home and the next morning when I go out to diagnose the problem the car starts fine.???!!!
I start driving it on short trips to the market etc and finally it failed and remains failed in my driveway (a curious thing to be happy about, I know).
I noticed the Tach did not move when the car was cranking. So I replaced the Crank Position Sensor. Still no start & no tach movement on cranking.
The car cranks normally and I charged the battery just to make sure that that was not an issue.
I opened the fuel rail - no fuel to speak of.
I checked for spark - none can be seen.
I pulled the ECU (the one on the right in front of the door) and found some light corrosion on the black plug's pins so I cleaned & dielectric greased them and checked the resistance between the Crank Position sensor and both wires checked out fine at the ECU plug. Put it back together and no improvement.
I swaped the relays at the front near the windscreen washer reseviour - no improvement.
I disconnected a lead to one of the coils as folks on this site said with the key in the run position they should have 12v there constant. I have nothing. Here I assume that one wire into the coil is positive and one is ground so I ran my tester between the two leads in both possible configurations with the key in the run position - not cranking. Is that right?
I visually inspected all the fuses.
ObdII, which I cleared after the installation of the fuel pump, shows no codes.

So here I ask for your combined experience and help with the puzzler.

Today if the rain stops I plan on checking the fuel pump to see if it works when jumped just to verify that I am dealing with one problem and not two.

Also, does anyone know if the crank position sensor fails does the car not get gas? In other words is it possible that I installed a new bad part.

Thanks in advance.
John

 

Looks like you've hit all the common points. I've added a link to your post to the list:


https://www.jaguarforums.com/forum/x...ngines-120221/


May take a look there and see if you've missed anything. Just Spit-ballin' here, but the last time you had it towed - didn't drop it off the truck rather abruptly did he? Might want to check your inertia switch just in case. Wouldn't explain your intermittent stalling issue, but would eliminate one more cause of no-start.

 

Hi John,

I'm sorry to hear of your longrunning issues. aholbro1 has collected a comprehensive list of threads on most of the known causes of starting issues, so it would well worth some time reviewing all those threads.

As you suggested, hard-to-diagnose issues are sometimes caused by an accumulation of more than one problem, which may be true in your case, so you may need to go several steps down the checklist before you resolve your issues.

To answer your last question first, it is not unknown or even uncommon for a new CKPS to not work, or for one or more of the contact pins in its electrical connector to back out of the connector as you are trying to connect it (I had read of this happening and didn't believe it until it happened to me). It would be worth carefully inspecting both halves of the CKPS connector to be sure the pins are undamaged and in their correct positions. If your tester is a volt/ohmmeter (VOM or DMM), it would be worth comparing the resistance of the new CKPS to the old one. Depending on your VIN, you can measure across the Red & Blue wires or White & Orange wires. The third wire is a shield. I can never remember what the correct ohm reading should be, but if both CKPS measure about the same, that may be instructive.


Charging a battery that is no longer able to hold a full charge may not help your diagnostics. It would be worth checking the voltage at the battery terminals while you are cranking the engine. If the voltage drops to near 10V while cranking, the ECM will not trigger the ignition.


Was the key in Position II when you checked for fuel at the rail? If you disconnect the fuel hose at the inlet to the rail (closest to the firewall/bulkhead), and turn the key to Position II without starting the engine, the fuel pump should run at least briefly to prime the system.

A lack of fuel at the rail could indicate failure of the Fuel Pressure Regulator and/or the fuel check valve, either of which is a common cause of poor starting and fuel starvation under certain conditions while running. These are problems most of our cars eventually develop, and I believe they are contributors to many hard-starting issues.


See my note later about the coil voltage.


I'm sure others will have different opinions, but since the definition of a dielectric is an insulator that can store a static electric charge, I personally do not use dielectric grease on the connectors of sensitive devices such as the ECM or sensors like the TPS, ECTS, MAFS, O2S, etc. that depend on variable signals in which a tenth of an ohm or volt can affect system performance. I use dielectric grease to help seal the two halves of the plastic connector housing, but not on the contact pins. My personal recommendation would be to clean the dielectric grease off with a good zero-residue electric contact cleaner spray.

The coils all receive a constant 12V supply on the White/Pink wires, but they are each grounded separately by the ECM to fire them, so you weren't getting a ground for your measurement. You can measure for 12V between the White/Pink wire of any coil connector and a ground stud (or a good engine ground).


You mentioned that you swapped around the relays near the windshield washer fluid reservoir. According to the Electrical Guide, the relay nearest the reservoir is the Fuel Pump Relay. It would be worth checking the relay base for corrosion on the terminals, and checking the relay for proper operation (or buying a new relay since good affordable equivalents can be purchased at most auto parts stores, and good Bosch relays often show up on eBay at low prices).

Please keep us informed!

Cheers,

Don

 

Thanks much for the quick reply and helpful information; alohabro1, your "start your engines link is great and I reviewed it thoroughly before I posted. The last tow was at the end of a cable as it was just a 1/4 mile from home. I thought I read that the inertia switch is not on the American market cars (though I may be wrong), but I feel this is not the problem.
Don B: Thank you for the input

-I rechecked power to the coils and yes, I have 12v there. Still no spark from the coils when the key is turned (checked 2 of them).

-Thanks for the heads up on the Dielectric grease. I will clean that up.

-Checked both old and new Crank Position Sensors for resistance across orange and blue wires - 8 ohm on both (does this mean both are good or both are bad?) - connectors on the female ends are intact and tight and check out all the way to the ECU. Since I have no movement at the tach when the engine is cranked, could the problem be in the ECU itself or will the signal be sent to the tach no matter what?

-This may be helpful - when I turn the key all the warning lights on the dash come on. After a few seconds all go out except the oil and battery lights. These remain lit even after cranking. Battery meter shows 12.8 volts with the key turned on and dips to 11 while cranking. A meter back at the battery surprisingly shows similar readings in both cases. Given this, are we safe in eliminating the battery since the problem first manifested itself while the car was running?

- It is too wet out today to mess with the fuel system. I know where the pressure regulator is, but where is the check valve located?

-While the ECU is out to clean off Dielectric grease should I open it up to see if there was water infiltration? My car does have the sunroof, but I have never seen any signs of water there besides the minor blue fluff around inside of the black connector.

 

Hi John,

The U.S. cars definitely have an inertia switch (see the recent thread below in which Ross helped the owner diagnose a tripped inertia switch). But I tend to agree with you that your symptoms, at least up to this point, don't sound like the inertia switch, since once it is tripped the car won't start or run at all. However, since your car currently won't start or run at all, it would be worth checking the switch if only to rule it out:

https://www.jaguarforums.com/forum/x...-start-121462/


You won't get any spark unless the engine is cranking and the ECM is enabling the ignition.


As I mentioned, I can't recall the correct resistance range for the CKPS. Search the forum for that bit of info because I'm sure it has been reported multiple times.

The ECM receives its engine speed signal from the CKPS in the form of a series of pulses that varies in frequency along with engine speed. The ECM then passes this signal along to the instrument cluster, TCM and Air Conditioning Control Module via a Purple wire with a Yellow tracer line. That wire goes from the ECM to a black 20-way connector near the right-hand A-pillar behind the footwell scuttle panel. At some point after that black connector there is a splice where the Purple/Yellow wire splits into three separate Purple/Yellow wires that feed the Cluster/Tach, TCM and ACCM. I didn't get into all this previously because I didn't think a problem with any of those wires would prevent the engine from starting, but I could be wrong. A problem in the ECM could certainly contribute to or cause your issues.

Since most affordable voltmeters do not react instantaneously to voltage changes, the fact that your cranking voltage is dropping to 11V on the meter probably means it is actually dropping even lower, and your battery is a definite suspect for the starting problems. I can't say that it would cause the stalling problems you've had, though.

I believe that on the X300 the check valve is built into the plastic evaporative flange on top of the fuel tank. I believe the flange is no longer available as a replacement part, so the easiest thing to do is to add a new check valve in the fuel line that feeds the fuel rail. Below is a link to photos showing how I first installed a check valve in the hose near the fuel rail on our '93, then moved it to beneath the fuel tank while I had the rear end out to rebuild the diff. Your car may be set up a little differently, but principle is the same. The second link is for an album that shows the replacement of the FPR on our '93:

Welcome to Jag-lovers - Members Photo Viewing Page
http://www.jag-lovers.org/snaps/snap...?id=1366662355


It would definitely be worth opening the case and inspecting carefully for any signs of water ingress or solder joints that are cold, starved or cracked. Some of the circuit board components may be sensitive to static electricity, so if possible ground yourself to discharge your own static electric cloud before touching anything inside the ECM. By the way, since the X300 has several Electronic Control Units (engine, transmission, air conditioning/climate control, anti-lock brake system, etc.), Jaguar adopted the term Engine Control Module and the abbreviation ECM when referring to the ECU that controls the operating parameters of the engine (fuel injection, ignition timing, etc.), so that's why I try to consistently use the term ECM (though I sometimes forget!).

One final thought - still thinking that your car may be suffering from multiple issues, it would be worth checking your transmission fluid level and condition, since a low (or high) transmission fluid level is known to sometimes cause engine stalling. Since your engine won't currently start, you'll only be able to check the COLD level of the fluid, but as soon as you get your engine started I would suggest checking the transmission fluid level once you've taken a good drive and the fluid is HOT. If your transmission fluid is low, that could cause stalling, and if your FPR and/or check valve have failed, the sudden release of pressure in the fuel rail could allow the fuel to boil, causing classic vapor lock after the stall that prevented the engine from starting until the hot fuel vapor in the fuel rail cooled and condensed (maybe about the same time the tow truck arrived, when they were able to start the car and drive it onto the tow truck).

Cheers,

Don

 

So, a friend loaned me some bits to open my Engine Control Module. Things do not look good for our kitten. It looks like there was some definate water infiltration at some point (one would think at least some small attempt would be made to seal them). There is corrosion around the black card (the red card sits 1/2" above the bottom of the case so no corrosion there). So today's questions:
Is there a way to make sure that this unit is dead - aside from no reading at the tach, no power at the fuel pump relay and no spark?
Is a replacement ECM more than the value of the car?

 

Hi John,

Hopefully some of the members who have replaced their ECMs will reply - I'm fairly certain some owners have purchased salvaged ECMs from eBay and used them successfully. I am under the impression that you can use an ECM even from a '96 or '97 X300, which may have some firmware upgrades and minor tweaks of the fuel and timing maps, however, you cannot use an ECM from an XJR (supercharged engine). I hope someone can reply who has actually done an ECM swap.

Cheers,

Don

 

If the model is the same, go for it. If not, swap the plugged EPROMS from old to new. I have swapped MY 96 VDP to MY 95 base with NO detectable difference (except the two were Re-oriented with different O2 sensor positions). If you need an explanation for that, check "reorientation" in the archives or ask and we can try and explain the evil that went through some Jag engineers brain way back when!

 

Right now I am actually running switched ECU's from a 1996 XJ6 base and and a 1997 XJ6L. No notable difference in performance yet from either car.

I have switched ECU's between the 97 XJ6L and my 97 XJR and that was a mistake. The XJ6L didn't idle correctly (RPM would fluctuate from 800-1500 constantly). Although the XJR idled fine with the N/A ECU, after switched them back, the idle on the XJR is at 1200-1400rpm in park/neutral and reverse/drive idles at 800-1000rpm. Not exactly sure how to fix the issue but within the next few days I'll be trying to get to the XJR throttle body to clean out any gunk. Removing most of the supercharger is what's the toughest

 

In addition to different fuel maps in the ECU between the different models (the XJ6 vs the XJR), there are some stored parameters that make the ECU match the car. First is the O2 sensor orientation, which maps the connected sensors to what cables they connect to and the other is the calibration otherwise known as span and zero for the TPS.

Although I have not personally done so, I am pretty sure that swapping the EEPROMS can even make an ECU match the NA vs SC model.

 

Thanks again for all the help and suggestions. I cruised eBay last night and was pleased to find that used units are much less than I expected. I am hoping that this is a nice plug and play (drive) solution. It actually makes sense since the first time the problem manifested itself was in a torrential down pour. Afterward it happened regardless of the weather so I never associated the two things. The downpour probably started the corrosion which caused random failures then finally a catastrophic shutdown. I will keep you posted as the situation develops.

 

Additionally, over time the ECM adapts both the idle speed and fuel metering, making baseline corrections to account for normal engine component wear. Those "Idle Speed Control" and "Adaptive Idle Fuel Metering" corrections are also stored in the EEPROMS, so if you followed Ross' suggestion to swap EEPROMS, those adaptations would also be transferred to the new ECM.

Cheers,

Don

 

Hmmh- I probably misspoke- The PROMS for the program are not writeable, so I expect the maps are stored elsewhere. I think the proms are only the "Configuration" and I believe the maps are lost on power down on an X-300, at least.

 

Sorry folks for the delay but my last post seems to have disappeared into the ether. I will not attempt photographs this time.
A friend came by with a professional electric testing unit and we traced the problem back to the ECM. We opened the ECM and it looked like it may have had ½” of water in it at one point. I am surprised that I only had an intermittent problem up to now! I ordered a used ECM via eBay supposedly good for a 95-96 car.
Original ECM: 4.0L N/A LNA 1410 AH with a sticker on the back that says R493 LNA 1410 AL then the hand written date of 10/31/2002
Used replacement: 4.0L N/A LNA 1410 FC with a sticker on the back that says R493 LNA 1410 FE then the hand written date of 2/21/2002
I connected the replacement unit and the car fired up right away – Good Kitty.
So I turned her off and reattached panels and covers and put away tools then started her again.
The engine now idles at 2000 rpm??? Well I take her for a drive hoping to introduce the new ECM to my kitty and little happened except after a mile or so the anti-lock brake and traction control lights illuminate.
I drove her for about 30 miles the RPM went down to 1800 but still a bit more enthusiastic than is normal. The Anti-Lock and Trac lights go out after every restart but return after a short run.
No check engine or codes.
Are the anti-lock and trac connected to the ECM???
Will the ECM adjust to my car?
Can I adjust, or have someone reprogram the ECM I bought or should I look for one with an “AH” suffix?
Did I possibly awaken a new gremlin in the anti-lock / trac con circuitry or is this also controlled by a slightly wrong ECM. (or did all my fiddling and testing mess up some other system?)
How long will my brakes hold out if my car wants to idle at 55 MPH? (LOL)
Anyone want a kitty free to good home? - Just kidding this is one of the most beautiful cars ever made!
For future forum users that need to buy a used ECM; mine only showed slight rusting/ corrosion around the bottom of the case, but opening it up revealed substantial water damage. Many of the used ECM units on sale (eBay) show much more damage to the case so I would question the integrity.
Again, thank you for all your experience and help. While searching for answers to this problem I found a few other items that need addressed that I was not even aware of.
Will keep you updated in case anyone in the future can use this post.