FF 17: Now Cranks but no start
 

Hello all,
I have been driving my 1990 XJ40 for about a week with the check engine light on. Prior to this, the check engine light would come on occasionally but would turn off if I shut down the car and restart it. Yesterday, I finally got a chance to do some work on the car.
The VCM code indicated was FF 17, which says that there is an issue with the TPS circuit.
I disconnected the - terminal on the battery to clear the code and when I reconnected the battery and started the car the check engine light was off.
I decided to drive the car to see if the light will turn back on and after driving the car for about 1000 feet the car stalled out and would not restart.
What I did notice was while cranking the light which I believe is the transmission light (on the dash it is the topmost light on the left side) stayed on.
I also noticed that my tach needle did not move while cranking the engine. suggesting that the CPS suddenly failed.
This morning I did the resistance test on the CPS and the reading was 1.2 ohms on the 200K scale. As per others the reading should be 1.3 + ohms.
Yesterday, with the temps in the 80s, I tested 2 used CPS's that I have and they both read 1.3 ohms. Today, with the temp in the upper 50s they now read 1.2 ohms.
I am tempted to try one of them on the car to see if it starts but the numbers are different.
The one that came off the car is DBC2139 and the used ones I have are DBC11501.
The difference between them is the size of the connector to the main harness.
My questions therefore are:
a) What is the correct resistance reading for the CPS?
b) Can I use a DBC11501 in place of a DBC2139?
c) Why would the car stall out after clearing the FF17 code
d) Why did the transmission problem light turn on while cranking the engine?
e) Did the change in ambient temp affect the resistance readings of the CPS?
f) Should I purchase DBC 2139?
Any and all help will be greatly appreciated.

The TPS has 2 circuits (six wires). One for the engine and one for the gearbox. The TCM wants throttle info also.

bob

Just my opinions, don't take them to the bank ...

Pretty sure your CPS is duff if the tach doesn't move.

a) What is the correct resistance reading for the CPS? Don't know
b) Can I use a DBC11501 in place of a DBC2139? Go back to the yard and get a plug to match your harness and wire the spare up
c) Why would the car stall out after clearing the FF17 code? I don't think it would and in fact it didn't, you drove 1100 yds.
d) Why did the transmission problem light turn on while cranking the engine? Overthinking? Aren't all warnings lit til engine fires up?
e) Did the change in ambient temp affect the resistance readings of the CPS? Don't know
f) Should I purchase DBC 2139? If you can't get a plug to match your spares, go ahead get one

good luck

Larry

CoventryWest has used CPSs for sale $124 plus shipping. They tested three of theirs and they get resistance readings of between 1.2 and 1.3 ohms. Pretty much the same readings as mine. I was also told that I can switch the connector from the DBC2139 to the DBC11501 with no issues, that it is done all the time.
More reading tell me that 1.3 ohms is what I should have. Is it likely that I have 3 CP sensors that are bad? All with the same reading?
Another thought is that my Ignition module failed.
Will continue to troubleshoot.

I did some more tests on the car.
I have fuel at the FPR connection. Fuel Pressure ??
I have spark. Whether the spark is happening at the proper time, if the CPS has failed: I don't know.
Reference and signal voltage at the TPS is within specs.
I tried two of the three CP sensors I have to no avail. With the ambient temp up to the 60s, both CP sensors are reading 1.32 ohms. The 3rd I did not use because the wiring is all messed up. No fluctuation of Tach needle.
I tried two other ignition modules, even though I had spark with the original Ign. Module.
Next, I will check the fuel pressure and see if the injectors are firing.
Any ideas????

Jaguar issued a Tech Guide that we were to follow for guidance/diagnostics. We were issued a copy but it was a paper three ring binder document.
Later Jaguar converted it to .pdf so I downloaded it also. Please search the internet (or Gus's site or even this forum) for......
S91_AJ6 4.0 Engine Management.pdf

I cannot upload it to this post because it exceeds size limits (it is over 13mb).

bob

Thanks Motorcarman. I will do a search for it.
I have narrowed down the problem to "No Injector Pulse" I used a NOID light and it does not pulse.
Can anyone give me some guidance here?
I read on this forum that the problem could be a fuse or the main relay.
The post in the forum says that Fuse C1 provides power to the main relay. However, Fuse C1 on the right side is for the radio and Fuse C1 on the left side is a 3 amp fuse that says "see handbook"
Has anyone diagnosed a "NO INJECTOR PULSE" issue so I can get a starting point? By the way, I also used a test light and I have voltage on both injector terminals on the injector harness, and it seems that the ECU is not creating the ground to pulse the injectors. When cranking the test light stays "on"
Am I looking at a fuse, a relay or the ECU?
Help please.

I have heard of issues that can be cured by unplugging and re-plugging the ECU, (but no direct experience with the process) - could be worth a try though?

Bob's S91_AJ6 4.0 Engine Management.pdf is here:

engine management pdf

Larry

ps I found this on another forum, just an FYI

and someone else posted this about the CPS:

Thanks Lawrence. I installed a new CPS ---$344 from CoventryWest. A used one was $124. TACH now reads 200 RPM while cranking. As I said in my previous post, I now have no injector pulse.
I removed the ECU and the numbers are kinda funny. There are 2 stickers on the ECU.
One says Jaguar: JAG331R
The other sticker say "Remanufactured by Lucas Automotive" and the number is LRZ 196. Written with a pen is the number 3391.
I am trying to cross-reference these numbers just in case I need an ECU, but I am coming up blank.
What is the DBC number for a 1990 XJ40 ECU or the correct number for same.

You have to search by VIN rather than model year but the Jag heritage site should have the part number for your car

https://www.jaguarclassicparts.com/u...xj6-xj12-parts

Are you sure you have no pulsing? The post above suggests pulses are so short that they cannot be detected with a voltmeter ...can you hear them clicking or smell any fuel when you crank the motor?

Larry

No pulsing at all. I used a Noid light and also a test light. With the very short pulse, like on any other EFI system you should see some dimming indicating a pulse. My car shows a constant bright light with the test lamp and no light at all with the Noid light because it is connected to the two terminals with 12v on each terminal. When the ECU grounds the appropriate terminal the Noid should light up. So no ground is being created by the ECU.
I will be looking at the ground pins for the injectors at the ECU harness and continue troubleshooting from there.
Based on the diagnostic procedures for the ECU, I have the following:
Constant voltage: Pin 14 of the Blue connector.
Switched Voltage: Pin 1 of the Yellow connector and Pins 10 and 22 of the Blue connector.
Ground: Pin 18 of the yellow connector and Pins 11,23 and 24 of the blue connector.
That is where I stopped for the day.

Ground Problem? Pin 18 of the yellow connector and Pins 11,23 and 24 of the blue connector should read 0 ohms as per the diagnostic tree from the Engine Management Section.
The readings I get from all 4 ground pins at the ECU is 4.55 ohms.Therefore High Resistance.
My question, before I go any further (since it is not stated in the Diagnostic tree. All it says is to correct issue.) is whether the grounds should be checked with the harness connected to the ECU or disconnected from the ECU?
Does anyone know?

Wouldn't hurt to clean all the grounds in the engine compartment - Don has all the where's and how's in the archives.

Larry

UPDATE: I am still banging my head against the proverbial XJ40 wall with my car and don't know what to do next.
As I stated in my last post, I had high ground resistance, which I corrected yesterday by cleaning all of the ground connections I could find in the engine bay. Ground resistance is now 0 ohms and I have continuity between the ECU and the fuel injector harness but still 'NO INJECTOR PULSE'.
I have spark, but I noticed that it is not a very strong one and it is orange rather than blue. Coil replacement in my purview.
Tach reads 100 RPM rather than 200 RPM
The FF 17 code came back when I checked the VCM for codes. I don't know if it came back because I may have cranked the engine with the TPS disconnected. Just in case, I have a good used TPS (based on the resistance readings). Rather than drill holes to flush the oil out of the TPS, I carefully opened it and cleaned it out. The cover I removed is hinged on the side where the wiring harness exits the TPS. After cleaning, the cover clicks back together and the resistance readings show it to be within specs.
I also acquired another ECU. Part #DBC6352.( Whether it is good is another story). I swapped it out but the problem still exists.
To the XJ40 gurus, please give me guidance on the following:
a) Causes of 'no injector pulse'
b) I have spark, so the CPS and Ignition Module appear to be good. Y/N. I also have good fuel pressure. Tested at the FPR inlet side.
c) Will a weak spark cause the injectors to not pulse
d) Will a faulty TPS cause a crank, no start condition?
e) Best method to test the Pink/Black wire at the ECM to see if the ECM is generating the ground to pulse the injector, meaning if I can see the pulse there, the problem will be in the EFI harness.
Thank you all in advance.

I feel for you mate! Must be really frustrating at this point.

I once had an issue with a recurring check engine light (not on the Jag) the whole time I owned the car and I replaced a lot of things chasing it.

No matter what I did, it always came back on and I finally found the problem two weeks before I sold the car.
What had happened was that when I got it, the check engine light was on. This was an 80's car with very basic CE light solutions so I had the o2 sensors replaced by the dealer.

With new components I never again went back to the sensors looking for the problem, but the issue was with one of the sensors - not the sensor itself but the plug/connection to the harness, When the mechanic fitted the new sensor, one of the pins in the connector had pushed back into the holder so there was no connection. As the connector was out of sight, the connector was opened and closed by feel - it was only by accident that I happened to open it up from under the car one day and saw the problem.

I guess what I'm saying is that you could check ALL your sensor plugs, TPS, MAF, & CPS connectors to make sure they are good and have no dielectric grease in them.

Hopefully someone else on the forum will have some better advice or some experience with the same issue.

If you want to eliminate spark/coil issues you could try spraying easy start into the intake and see if she fires up. Bear in mind that a low battery will allow cranking but will prevent the car from starting.

Out of ideas, sorry

Larry

Thanks Lawrence.
My battery voltage is good and in between diagnostics, I keep it on a charger.
I have checked and double checked each and every associated electrical connector on the car.
I am also out of ideas, so I took the car to a shop that only deals with British cars for Diagnostics. Bit the $105 per hour diagnostic fee bullet.
They have the PDU scan tool for the XJ40. Sometime tomorrow they will let me know what they found.
Keeping my fingers crossed.

Good luck!

Larry

RESOLVED: Faulty Ignition Switch.
12 v to Main Relay with Ignition "ON"
0-2 v to Main Relay during the cranking mode.
Ignition Switch replaced with a used one. I will see if the faulty Ignition Switch can be repaired.

Oh well, a few bucks well spent then? Glad you finally nailed it, I never would have guessed that was the problem, but will make a mental note!

all the best

Larry

Thank you. As we can see, working alone has it disadvantages.