When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hello, anybody have any experience with the actual sensor trigger position , from what info i have the CKS sensor flag is supposed to be 10 degrees BTDC mine is way past and my engine runs terribly. This is on 1996 ,with the attached picture looking through a mirror the engine is at TDC on 1A cylinder, if you look closely at the damper you can see the timing marks from the factory machined in. CKS sensor with some sort of reference picture using a mirror of damper at TDC yet flag is at ATDC
The CKPS position on the original installation is not adjustable. I've had my damper off but don't recall any timing marks, only the pointer bolted to the rear of the damper. It is not usually a concern since it can only go together one way.
I don't know what the original "BTDC" factory spec position for the sensor is, but advancing it would be beneficial for power and efficiency just as the Andy Bracket works for the AJ16 engine. I believe the sensor mount is attached to the timing cover and would require some metalworking to accomplish a physical advance.
Of course if your sensor is bad, the engine will not run well.
I don't have this engine so looking as an outsider
What is the relationship of the Camshaft Position Sensor in relationship to the Crankshaft Position Sensor ?
There are adjustment considerations as well as how they function together considerations ?
Is the Camshaft sensor supposed to only used in the starting sequence and then reverts to the Crankshaft and that not acuring ?
Can you mark the Harmonic Balancer pulleys with white paint to check for slippage using a reference point to each pully or the missing toothed gear to the rear of the pulleys ?
The Crankshaft sensor will probably read 1300 ohms as a basic meter reading if it is a traditional inductance sensor
Do you have engine tachometer reading as the engine runs ? This not missing does not necessarily mean the CKPS is working as a whole being a good enough single signal for the tach gauge but not good enough for the ignition timing
The only part of the harmonic damper/pulley that can slip, if the rubber bonding deteriorates, is the bit that drives the alternator. The timing trigger is bolted to the damper hub which is keyed to the crankshaft and therefore can’t slip.
If the rubber bonding deteriorates then only the alternator drive is affected, the timing is not and the engine will run normally until the battery voltage decreases due to no alternator drive. There will however be a lot of noise from the two parts of the damper banging around as the rubber bonding chews itself to bits.
The camshaft position sensor function is to there to tell the ECU whether the engine is on the compression stroke or the exhaust stroke when starting the engine. If this sensor is faulty then the ECU will attempt to start the engine anyway and if the first attempt doesn’t work it will try again one rev later. Once the engine is running timing is controlled by the crankshaft position sensor at the front of the engine and the engine speed sensor at the rear of the engine. I was curious so I disconnected my camshaft position sensor and tried to start my engine, it took a little longer to crank but started and ran normally.
In reference to the OP's timing trigger flag, it looks correct to me. The tab of the pointer is located at about 10 degrees BTDC when you take into account that we are looking at a mirror image, and also that the engine rotates to the left (counter-clockwise). The trigger will cross the sensor before the engine reaches TDC. This is my worn-out damper pulley with timing flag:
You don't have to send the timing flag ring OR the front two pulleys to Dale's for rebuild, but I sent the whole enchilada and he didn't complain.
Hello All, Thanks for all the reply's and help. It turned out to be a combination of a marginal CKS sensor ( 25 yrs old ) and a 0.047 gap between flag and sensor. I removed the sensor reference bracket and installed a shim to bring down the gap to 0.022. I also installed a timing degree wheel on the damper for a more accurate measurement. It is supposed to be 26 degrees BTDC according to the new info i found ( attached ) which is exactly what it is. As stated in previous post the flag cannot slip and the engine will run with the cam sensor disconnected but absolutely needs the CKS and RPM sensor to run. My next step would have been to hook up a multi channel scope to view all. Thanks again. Steve
Hi, After much in depth research for variable reluctance sensors the 0.020 gap is what most are universally set to for proper operation. I never could find the actual Jag spec. Interesting in my research i learned that vehicles that would have sustained front end damage or any area that houses this type, may have disrupted this gap causing issues. Another note these sensors have a + and - polarity and when connected backwards changes the timing event , again in collisions when harnesses need repairing and done in reverse by mistake. I previously thought 2 wires either way would work, not so. We all learn something new and pass it on to help others one day. Steve
This is my worn-out damper pulley with timing flag:
Revisiting: Who wants to be the first to advance the timing another 3 degrees or so? Easily done with the balancer off, enlarging the timing flag bolt holes. This would have the effect of improved power and fuel efficiency, similar to the Andy Bracket that has been super successful on the AJ16.
The Andy Bracket has a 5 degree advance, so 3 degrees here would in theory give an extra margin of safety....?
A possibly important consideration would be in reference to the compression ratio of 11:1 for the V12 versus 10:1 for the AJ16. Who can comment on this? Perhaps the Guru himself @XJRengineer ?
The V12 engine is less tolerant to advancing the ignition timing that either the AJ6 or AJ16 engines. If the car isn't driven hard or in high ambient temperatures, you would probably be alright on 95 RON (91 pump octane fuel), but I wouldn't like to say for certain. I would recommend 93 pump octane number fuel to provided an added safety margin.
XJ12 Timing Trigger
