Hi guys, I know similar topics have been discussed but I have a simple question here. Do camshaft position sensors go out of position and get "mis-timed" by itself?

My car was starting perfectly everytime for years, then slowly i started to experience the odd extended crankings. Fast forward to now, the car starts everytime but always with extended cranking. Car drives perfectly once started with no problems.

My fuel pressure is good, pump is good, fuel pressure valve + regulator is good. I have new coils. Crankshaft position sensor is new. I've cleaned the contacts and checked the wiring of the camshaft position sensor.

Before i go out and buy an expensive used camshaft position sensor, my question remains - do they go out of position by themselves? The bolt that holds it down is tight!

Best,
Kopi

 

No they do not.

Fail, erratic pulse, maybe.

Both mine were way out of time, so clearly removed by some Wombat, and simply dropped into the hole. Both had the new style top tensioner, so cam sensor had been out.

Once reset and secured, both start basically on the 1st rotation of the engine,

 

Thank you. I suppose the advice is to replace the camshaft position sensor?

 

There are two position sensors, one a camshaft position sensor the other a crankshaft sensor.
I can’t remember which is which (doh), but if the one on the front of the engine fails it will take a few rotations of the engine before the engine can workout when to fire the spark. Change the front sensor and hopefully this will fix your problem.
Or is it the other way around?

 

Maybe.

I am NOT one for throwing items at cars, it rarely acheives much, apart from draining the bank balance.

The attached PDF may assist in checking/setting this sensor.

ALSO

When was the throttle body inner bore last cleaned????. I would remove the intake elbow, take a solvent/petrol soaked rag, clean the GOO out of that body, including the disc itself. This is critical to a proper running engine, and hard starting on some has been conntributed to this. I clean mine at every oil change, simple.

The first time could take a few minutes, as the GOO bakes on, so just keep at it.

 

Hi Kopi,

You don't mention the year and model of your Jag, but assuming it's an X300, the camshaft position sensor (CMP) is certainly a prime suspect. As Cafcpete alluded, at startup the engine control module refers to the CMP to determine cylinder 1 top dead center on the compression stroke within less than one revolution of the engine. Once the engine starts, the ECM ignores the CMP and refers exclusively to the crankshaft position sensor (CKPS) for determining ignition timing. In the event the CMP signal is absent or implausible at startup, the ECM reverts to the CKPS signal but must use "trial and error" to determine cylinder 1 compression TDC, which can take 30 seconds or more. To accurately test the CMP requires an oscilloscope, but you could try disconnecting the CMP to see if the engine starts any differently. If the extended cranking is the same as with the CMP connected, this would suggest the CMP or its wiring has a fault.

Other issues that can lead to extended cranking include low cylinder compression, low ECM voltage while cranking, a failed fuel pressure regulator or fuel non-return valve (check valve), worn or fouled spark plugs, obstructed air filter, contaminated fuel, a lazy relay (such as the ECM Controlled Relay which provides power to the fuel injectors), and more.

If the ECM senses the voltage sagging much below 11 volts while cranking, it will not trigger the ignition to fire. One cause of low voltage seen by the ECM is corrosion on battery power connections and grounds throughout the car.

Have you scanned the car for stored diagnostic trouble codes? How long since your last tune up?

Cheers,

Don

 

Folks thanks so much

Grant Francis >> The attachment is super helpful, I will give it a go. No i have not cleaned my throttle body but I would've thought that it'd impact the running of the car as well.

Don >> It's a 1995 Jaguar X300 3.2. I forgot to mention, it does throw up code P0340! That's why i zoomed in on the camshaft position sensor issue.

I will try to check on the timing, but failing which i guess its time for a replacement. Will report back, thanks again.

 

I am generally in agreement with Grant"s view about not just blindly throwing money at a problem, but I would make an exception in the case of the Crankshaft position sensor on an X300! If you havent changed it before, it is worth changing (and easy too).

 

Hello there,
On my 1996 X300 XJ6 Base, 77000 miles on it and lived it's whole life in climate controlled garages until it came to my house in New England last fall. The car also has a stack of records and was well cared for. I think remember reading the CPS was changed at some point but need to dig through again.

I left out in about 25 degree weather the other night. My garage is concrete and can have moisture, so I go try to air out garage but also sometimes just keep car outside. When I went to start it, it took 3 tries before it fired. But its been fine since. In fact last night I took it on a 1 hour drive and had it through 4000RPM a few times. I drove it. Good fast drive. Anyhow I've heard a little about these Crank Position Sensors. I too don't like to throw money at parts needlessly. My question is, should I buy a spare crank position sensor and keep it in the trunk? If so, is a Standard Motor Parts an OK brand to buy?

I already have a spare coil.
With the coil, I acted as if I was going to Casino- I got a 15 dollar coil and a 35 dollar coil, I put the 35 dollar one in the motor replacing a failed coil. the 15 dollar one is in the trunk as a spare.

Thanks!
Basil

 

On the previous drive and the fuel pressure being trapped on engine shut off by 3 points including a check valve the fuel pressure should remain until the next engine start cycle where it is recharged by the short 4 second initial fuel pump run . The fuel pump will come back on in the present engine run by the CKPS signal for the duration of your drive

So you have on , off , on in the starting sequence

Ideally the fuel pressure should be trapped for days , 43 psi

The CKPS single signal can be failed to be good enough for the fuel pump enable but still give you Tach gauge and ignition / juel injection timing without a P0335 CEL code

A cheaper insurance policy would be to keep a fuel pump relay socket jumper wire as your spare

But this does not protect you from full failure of the CKPS which would strand you and the cost involved like time , tow , and others

The recommended jumper wire should have blade tyle terminals on it and not just jamming round wire into the sockets , the auto parts store can help fabricating this jumper from a tool and other items kit behind the parts counter

Your jumper sockets are the aft most socket to the fwd most socket or 30 to 87 , this will be hot at all times and drain the battery with your keys in your pocket

The aft most socket 30 is battery power

 

Hi Basils,

In 25 degree (Fahrenheit) weather, the most common cause of extended cranking is probably a cold and/or weak battery. The Engine Control Module will not trigger the ignition to fire if the voltage sags much below 10.5 volts while cranking. By the third try, the battery would have warmed up slightly due to the current flow from the first two tries.

Condensed water in the fuel tank or contaminated fuel is another possible cause of difficult starting.

It is possible that the Crankshaft Position Sensor (CKPS) was the cause of your hard start, but in cold weather I would be more inclined to suspect the above causes. The CKPS is a good item to replace preemptively since its various failure modes are often intermittent and difficult to diagnose. The original sensors were probably made by Bosch or licensed from Bosch by Lucas. Another excellent currently-available sensor is the NTK. The Standard Motor Products sensor may be just fine. What I recommend is that you change the CKPS preemptively and keep your known-working old one in the boot as an emergency spare.

What Parker is describing regarding fuel pressure is that the Fuel Pressure Regulator (FPR) and fuel pump check valve or non-return valve work together to maintain pressure in the fuel rail even when the engine is shut off. Over time, the FPR and check valve lose their ability to maintain pressure, and the pressure in the rail will decline slowly at best and very quickly at worst. This means that when starting the car, the fuel pump has to build pressure in the rail again before the injectors can atomize the fuel for combustion to occur. The fuel pump runs for a few seconds to prime the system when the key is turned to the ignition on position, but this may not be enough to build sufficient pressure in the rail. When this becomes a problem, you will usually have extended cranking at every start after the car has sat for awhile without running. Re-starting after a brief shut-down will often be just fine. Since your extended crank event was unusual rather than the norm, I would be disinclined to suspect a fuel pressure leakdown issue as your problem.

Given the cold temperature in which your problem occurred, I am more inclined to suspect your battery voltage was sagging too low while cranking. Many auto parts stores will test your battery and charging system for free.

Cheers,

Don

 

The size of the battery may also be a factor beyond the Amp / Hour rating sticker

Too tempting to have a standard size battery installed instead of a A8 size , ask me how I know

The large sagging voltage during start stumped me for a while

Keep the fuel fill well drain line clear as water can get in the tank degrading the fuel

 

I would agree with Don and Parker that the battery is a good line of enquiry to pursue. These cars like a strong battery, and can seem to crank well but be below the "magic" voltage level if they are not in top condition. Assuming your battery is the right size, what age is it? Nothing like a bit of cold weather to flush out a problem!

 

Thank you all again!! The Battery was new in 2020 and is the proper A8 size battery. I have ordered a spare CPS to keep as a spare. I have also made a jumper wire as advised and will keep it in car along with some spare relays and a spare coil. I also made sure fuel filler cap area was not wet with water. It wasn't but I vacuumed it out good and made sure it's nice and clear. I also pit a length of thin welding wire down that drain hose and it didn't seem to jam at all but I don't know exactly where that hose ends under the car so not sure it went all the way. It did go maybe 3 plus feet though and didn't seem to jam at all. This is a florida car so all the hoses look nice and new and there's just no corrosion anywhere on any electric connection anywhere that i have ever looked.

My main goal is to try and prepare for when this car does present a starting problem again especially if I'm on a trip somewhere.

Again I keep it in a concrete garage and it gets wet and moist in there. I do try and leave the door open so the thing can air out. But I dont think it's good to just start the car up back it out and park it outside. While this may help air the whole thing out, I do not believe it's good for the engine to start it and shut it down like that. It's just a lovely car. I just wonder whats better, starting it to move it outside in sun during day or leave it be in garage thats wet? what would you guys do in my situation? In the summer, it wont be an issue, I can leave it on street with a car cover on it. But I'd never put cover on if it's a bit dirty or wet. what would you guys do in my situation?

 

I have found that if you do not drive it often to put a trickle charger on it. Here is one that I have been using for years and has worked out very well. I also use one on my pickup that I also do not drive that often.

 

Hi Phil,

Thanks for that. I use a trickle charger sometimes but not always. for example, I had one on it yesterday, but will drive it tonight so took it off this morning. As a side note Your Jaguar there in the picture is the same as mine with same wheels but mine is white. Very pretty cars!

 

Sounds like you have the battery position well covered. I would maybe now circle back to the CAM position sensor. This fits in the hole left by the removal of the distributor, which became redundant with the introduction on coil on plug ignition. As described previously, if it is missing in action or maladjusted, the car will take longer to start, as it takes the ECU longer to work out what is going on, but thereafter it will run normally.
As a replacement for the distributor, the Cam position sensor is clamped in place, and can rotate. There is a little window which allows the correct position to be determined, and it might be worth checking your setting, as I am wondering whether it could have slipped a little?