Yep, Ross is correct it will start without the Cam position sensor. It might take 30 secs or more of cranking but it will get there eventually. Once the engine is started the I believe the CPS no longer has a role to play in engine management but is used to verify if the crank sensor is working correctly.

 

I am intrigued by the shift solenoid failure- maybe check the engine ground strap or measure the voltage betweem the engine block and the car chassis while cranking- should be less than .5 volts or so

No CEL, right?

 

It must read it, mine died and I got a secondary air code for some reason. Secondary air was fine of course but the crank sensor was gone. Also had terrible running conditions.

 

Yeah, no codes I actually keep checking with the hope it will set a code and lead me in the right direction. I'll check the ground strap, but suspect it is OK, when I checked voltage at the coil it was only .02V less than the battery. I'm not off again until Saturday, so hopefully I'll have something figured out by then.

The shift lockout is troubling. I checked all my fuses and everything looks OK. I'm going to sit down with the electrical manual and see what I can trace there too.

Thanks to all for your input!

 

Quote:
Originally Posted by sparkenzap
My name ain't Ripley, BUT, Believe it or Don't!, the X-300 will start without the CPS connected. I cannot say that it will start with a bad or severely mistimed CPS.

The manual is explicit. If the ECU does not detect a CPS signal, it will "try" both orientations of the crank to cam timing until one fires. This causes an extended crank until start, and is a diagnostic hint that the CPS might have failed.

Yep, Ross is correct it will start without the Cam position sensor. It might take 30 secs or more of cranking but it will get there eventually. Once the engine is started the I believe the CPS no longer has a role to play in engine management but is used to verify if the crank sensor is working correctly.
__________________
Cheers,

Allan


Ross & Allan,

Just to help me understand your arguments, have either of you actually started an X300 with the camshaft sensor disconnected? I've read the manual, and I don't find its language explicit, but rather "theoretical" or "hypothetical."

Here's the paragraph to which I believe Ross must be referring, from the Jaguar AJ16 Engine Management System Dealer Training Manual:

"The CMPS is necessary because the crankshaft position sensor (CKPS) gap identifies TDC position for both cylinders 1 and 6. Without the CMPS sequencing input, the ECM would attempt engine start by trial and error, firing each cylinder in sequence; several engine revolutions might be required for successful engine start. CMPS input is not required by the ECM once the engine is running."

Now, maybe that seems explicit to some, but to me it seems to be an explanation of the necessity of the CMPS in the AJ16 engine management system, not a declarative statement of an actual default behavior designed into the GEMS ECM in the absence of a good signal from the CMPS.... Is there another Jaguar manual that states it more declaratively?

And just to help X300 newbies like me who are trying to follow this thread, it might be helpful to agree on abbreviations for the Camshaft Position Sensor and Crankshaft Position Sensor, since the abbreviation CPS has traditionally meant "crankshaft position sensor" prior to the the advent of camshaft position sensors in engine management systems. Jaguar uses the abbreviations CMPS and CKPS to differentiate between the two, so can we agree to use them here?

Assuming Ross' and Allan's interpretations of the manual are correct, or that they have personally started an X300 with the CMPS disconnected, I here repeat two of their core statements using the Jaguar abbreviations for greater clarity:

Ross: "The X300 will start without the CMPS connected..."

Allan: "Once the engine is started the CMPS no longer has a role to play in engine management." After the engine starts, only the CKPS signal is referenced by the ECM for ignition timing. (this statement is definitely confirmed by the manual)

Sorry to be OCD - it just seemed that in order to best help ra.stewart it might be helpful to agree on the Jaguar-approved abbreviations.

Onward and upward!

Don

 

Don:'
I understand your skepticism which is exactly why I started that like I did! (Which are you, a lawyer or an engineer? )
And, I agree that the text you quoted is not explicit, (good eye!) and it worried me for a minute why I had not made the interpretation of it that you have. But, read the image below, from the shop service manual (NOT JTIS or the technical update) and I think you will agree it is explicit. And.. while we are on semantics, please note the use of "CMP" as well as "CMPS" in the manual text.

As to having actually cranked one without the CMPS, (the cam position sensor in X-300 glossary), I think I have, but I cannot say for sure, but I know it has been reported to be the source of slow to start conditions. I WILL pull mine off just to be sure, but I have no reason to doubt the manual.

TXT:
CAMSHAFT POSITION SENSOR - CMPS
Monitoring Procedure
If the engine is turned and there is no camshaft signal, then
a camshaft sensor fault is present, so the system is synchronised
using the crankshaft sensor alone. Synchronization
ensures that ignition coils are actuated in the normal sequence
but if after a number of engine revolutions the engine
does not start, then the actuating sequence is shifted by
one engine revolution. If after a number of engine revolutions
the engine does not start, then the sequence shifting
is repeated until the engine is running. To detect faults the
crank and camshaft sensor outputs are cross checked plus
a crankshaft ‘missing tooth’ position check.
The strategy will report to the Diagnostic Status Manager(
DSM) when a crankshaft inaccurate fault is present and
the DSM will then decide whether to store a fault code and
illuminate the MIL Lamp.
The CKP and CMP are tested by cross checking the output of
the sensors and identifying when only one sensor is operating

 

Hi Don,

As usual I am in agreement with Ross

I agree that words mean things and in my statement I probably should have said 'ignition management' rather than 'engine management'. In this case the function of the CMPS is to identify TDC of the compression stroke of cylinder #1. Once it has given the ECM that info, it has no more to do with ignition management. Ignition timing is then only controlled by the signal from the CKPS to the ECM.

This is the text from the description of the CMPS which explicitly states that it is not required once the engine has started.

 

Hi Allan,

I completely agree with your statement above. It was your prior use of the abbreviation CPS to represent the Camshaft Position Sensor that I was concerned could be confusing to ra.stewart (what IS his first name, anyway?)

Cheers,

Don

 

[QUOTE=sparkenzap;930247]Don:'
I understand your skepticism which is exactly why I started that like I did! (Which are you, a lawyer or an engineer? )

Ross,

Many thanks for the additional information. I agree that the manual you quote IS explicit. If you get a chance to confirm that your X300 really will start with the CMPS disconnected, then the matter will truly be put to rest.

I'm neither a lawyer nor an engineer, but my Mom always told me I should have been a lawyer, and my Dad was an engineer (he designed water pumps and fuel pumps for the Big Three, Toyota and others) and his father worked for NASA at Cape Canaveral. Sorry to be so insistent on technical accuracy and clarity...I guess it's in my genes.

Cheers,

Don

 

you talk about crank sensor, can you tell us where is this located and how it looks?

 

Squirting oil into each cylinder instead of gas? Are you serious?

 

Sorry I meant the Cam Angle Sensor.

 

yes thats correct to restore oil film on a cylinder wash down. But he has compression so this is nto a issue. But fuel wet plugs can be a issue.
also you CAN unplug the Cam sensor and it does then look at the crank sensor for starting if it sees NO signal. Now a poor or incorrect signal is another issue. Look at the fuel pressure reg for internal fuel leakage into intake also if you have wet plugs, just another source. Thats my lunch break time tip

 

I just don't understand this at all. On other engines I have had serious flooding of the cylinders but OK compression. What's so special about this engine that flooding which ought to be rare anyway being injected causes a lack of compression?

Mike

 

The cylinder wash is a conditionthat is fairly well known for higher mileage examples of Nikasil engines like the Jaguar AJ26. Some claim this can happen to any engine, but I am pretty skeptical.

Time-pilot:
Can you not see or read my embedded diagram above? Geez, dude, it does take some effort to post this stuff!

Cool:
The CKPS is located on the front of the engine reading the teeth at the back of the crank damper pulley.

 

I read it, just unplug it and drive around, things won't go well.

 

its most common on the early nikasil v8 not this engine. But it can happen to most any engine. That early v8 have low tension rings and need a oil film to have compression. Wash it off and ive seen 20-30 psi. Squirt oil in cylinder I usually only did one bank and that was enough to start and then oil slung off the crank coated the walls and compression restored and ran fine after that.

 

If you watch any of the classic car shows like "Chasing Classic Cars," they add oil to the cylinders of the engines of just about every car that has been sitting for any period of time. I think this is both to free potentially frozen piston rings and help prevent breaking them, and to restore compression to help start the engine. A common product used for this operation is a so-called "Top Oil" (meaning a lubricant for the cylinder head and fuel system), such as Marvel Mystery Oil.

Cheers,

Don

 

There are pictures of it in XJREngineer's thread: https://www.jaguarforums.com/forum/x...engines-66536/ somewhere. Not sure which page.

 

OK, I confirmed that mu MY 95 X-300 NA engine will start without the CMPS connected. It took a while- Maybe 25 seconds- just about the time I was thinking I was going to proclaim the book wrong!

And Time Pilot, although I really don't know why I am bothering to reply to your snipey comments, no one here was suggesting taking the CMPS cable off "and drive around" as a normal procedure. It is a diagnostic method to show if the CMPS being mistimed or screwed up is causing the No- Start. As I said, Geez.