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Discussion Starter #1
Hi All,

I have a problem with my UK Range Rover P38 1996 4.6 Auto

The Crank sensor (CKP) is mounted through a plug in the bell housing. This plug (It transpired) was moving. This first caused a problem where on hard acceleration or when reaching a speed >70mph the car started to misfire. Once this happens the engine has to be switched off and on again, it is not possible to drive through it. Once engine is switched off and on again it will run fine.

When I first had this problem I removed CKP and could see a marking on the black part of the CKP where it was touching the top of a tooth. I spaced it with a washer each side and it ran fine for another 4000 miles.

On a trip to Ireland the problem re-occurred. I removed the CKP again and found the bung/plug to which it is mounted is loose (on the inside of bell housing). It is now so loose I can push it in by hand and twist it about.

There is a LR tech bulletin on this and a bracket was fitted to the CKP to keep it in place. Mine does not have this.

I have now tried to centre it as well as possible to the trigger teeth, but tbh it is a bit of a guess given the access and then made a tool to allow me to pull the bung back into the hole. However, trying to centre (not skewed in the hole) is again a guess and I have no idea how far it should pull out, ergo it is unlikely to be in exactly the same place. Later today I will be trying to space the sensor depth so it does not touch the teeth and seeing if it works... If so I will epoxy the bung in its location and cross fingers it does not come loose....

If not I am looking into a crank mounted trigger wheel behind the pulley (same as my TVR) as an alternative to removing the gearbox.

Does anyone know the following...

Is it possible to pull the bung/plug out from the outside (appears to not be possible so far..)?
Is the plug/bung keyed in any way so that it will only pull back in place with the correct alignment (does not appear to be)?
If I go trigger wheel, can I just use a 36-1 trigger wheel behind the pulley? I have seen mention of a 36-2 and 36-1 for GEMs P38 - I can check this tbh.
I have read that Gems CKP is set to 20 deg After TDC Many of the ones I have seen only have 4/6 bolt holes, I will need one with slots to time correctly?
Does the Pulley then have to have the reverse machined to remove the width of the trigger wheel (assume it does)?
Will any two wire crank position sensor work? Any suggestions on mounting - I made one for the TVR so not really a problem to mount?
If I do choose to pull the gearbox inc bellhousing to get at the bung/plug I assume the reluctor ring is attached to flywheel. This will still make locating the plug/bung in the correct position in the bellhousing very difficult/impossible.

Any other suggestions that don't involve pulling the gearbox although I can do this if I have to.

Thanks,

Matt
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

Have you not thought about getting it welded in, or chemical metal to hold it in place. Maybe try a few of the LR breakers to see if they have any u/s lumps with the bracket addition.
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

Absolutely, my first plan is a best guess at location and epoxy it and see how we get on... If I can get it in the correct position without removing the box then I can make/buy a bracket to keep it there. Just taken a look and the CKP is in the engine casting (I think) so I could align it if I can move the box back.

It looks like with props removed and exhaust off I could shift it back far enough to get at the crank sensor from inside align it and secure the mounting plate/bung/plug in place.

I have seen mention of a a cover plate that you can remove to see the CKP and the teeth from the inside. The only cover plate I have is at the bottom secured by 3 bolts and you cannot see the teeth or CKP through it. I can only guess that this is different on the box used in the 4.6 unless I am missing something obvious...
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

If it helps, as far as the GEMS reluctor ring:
The reluctor ring has a set tooth pattern, 60 teeth are spaced
at 6° intervals and are 3° wide, two teeth are removed to provide a reference mark at 60° BTDC for number 1 cylinde
r
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

On a GEMS you can drop the plate off that covers the lower part of the flywheel and you might be able to see it by looking up from underneath. According to the parts list, the ring that holds the CKP should be secured with a roll pin but from the exploded diagram it looks like that has to be fitted from behind so would still involve moving the gearbox back. I've found that as the gearbox is such a big heavy lump, moving the engine forward on an engine crane is easier. If the viscous coupling and fan are taken off, then there's plenty of space at the front for it to move into.
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

As above, if you've got to get a space, I'd pull the engine forward as well, the plate mentioned is held on by 4x8mm, 2x13mm head bolts, I'm wondering if you could get something other than a roll pin in, with everything in situ, and try to adhere that part to the bracket, I've just got rid of the gems block I had, so can't go and have a look. Hope you get it sorted without to much hassle
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

have you tried to contact RPI with your concern? they may have a solid solution to your concern.
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

They will but their suggestion would likely to be to buy one of their blocks at £8k each.......
 

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Discussion Starter #10
Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

Thanks All,

Ferryman.

That bracket looks a lot like the plug/bung that is standard fitment and already there (The bit that was loose).... This would require the engine gearbox to be split and, of course I already have one there minus the welds and rollpin....:)

I believe there to be a bolt on bracket fitted to later GEMS models and which will retrofit, but I maybe wrong...

Orangebean

This is a GEMS engine and I am pretty sure it is a 36 tooth reluctor at 20 ATDC. The later Bosch/Thor used 60 tooth.

Chris no 10

I assume you mean the half moon shaped bracket that fits to the bottom half of the bell housing (I have one on my TVR secured as you describe)

There is no such thing on my engine, the bottom of the bell housing mates directly to the sump casting.

There is a round plate at the very bottom of the bell housing secured by 3 bolt, but you can see bugger all through this.

So.... I took my best guess/attempt at measuring and epoxied the mount in place and went for a drive. It was fine when cold, but as soon as it got warm it started to missfire worse than ever. Would not even run properly when the engine was cycled on/off. Strangely enough, after it cooled it ran up again fine. Car can be driven as long as hard acceleration and speeds over 70mph are avoided.

My next step is to check all the teeth are there and straight and the gap between the teeth (either side) is equal.

I will then see if I can butcher one of my CKPs to make the black part, where it fits in the plug/bung, smaller to allow me a small amount of adjustment - this might knacker the CKP of course but worth a try.


It has occurred to me that the Intermotor (I think, definitely cheap) CKP is failing after 4000 odd mile and that this was the original cause.... and then I disturbed the plug/bung.

By the way I have a Nanocom and when it got really bad it threw a camshaft sensor fault, but it does not usually do this when it misses. No surprise if the timing is out.

I also forgot to mention that when it missfires the tacho jumps about.

I am away for the next ten days so will get back on to it when I return....

Lastly, my diagnosis of CKP is down to the fact I have both petrol and LPG and it is the same on both. I had this same issue previously which was cured by the addition of spacer washers and at that time I bought a new CKP and it did the same on both new and old before I added the washers.
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

Orangebean
This is a GEMS engine and I am pretty sure it is a 36 tooth reluctor at 20 ATDC. The later Bosch/Thor used 60 tooth.
Apologies- the GEMS is:
The output signal from the CKP sensor is obtained
from the magnetic path being made and broken as the
reluctor ring teeth pass the sensor tip. The reluctor
ring has 35 teeth and one missing tooth spaced at
10°intervals. The missing tooth is positioned at
20°after TDC.
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

Misfiring, and sometimes simply dying, is a classic symptom of a failing CKP sensor. You can prove it easily enough by chucking cold water over it to cool it down when it starts to misfire. If you have the alloy sump that incorporates the lower flywheel cover, someone has changed your sump for one from a later Thor engine. The GEMS should have a pressed steel sump and the separate plate whereas the Thor has the all in one alloy casting.
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

As imonly says, it does sound like the crank casing has been changed, otherwise you can't get at the torque covertor bolts.
It does sound like you've diagnosed the fault, these cars must have original parts on such important sensors, I once replaced the tps with a cheaper one, was like being kicked up the backside above 50 as it misfired,,
Can't see where in the world you are,, if uk I might have an original sensor you can have,,
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

It looks like someone has been there before you and did a bodgejob glueing the bracket in place by lack of a TIG welder.
You have to shove the engine forward (or the autobox rearward whatever you prefer) to get a close look.
As for having a alloy sump, just remove the rubber grommets to reach the TC bolts, which one depends on the flywheel you have, GEMS or Thor.
I had my bracket changed too, when I converted a Gems block into Thor to suit my 2000 model year.
Not an example of fine welding but it does the job.
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

As for having a alloy sump, just remove the rubber grommets to reach the TC bolts, which one depends on the flywheel you have, GEMS or Thor.

I'm pretty sure that the access to the torque converter is on the block Tony, above the starter, ( Thor engine) I don't remember it being on the sump pan. I might be wrong ! But if I'm right and they've swapped sump pans the only way he can undo the converter will be remove sump first..
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

Sorry Chris that I have to disagree.
As you see the pic of my TC still on the box, the nuts are welded on the backside of the flange. To undo the bolts you reach them through the 'grommethole' of the alloy pan, through the flywheel onto the driveplate.
Tony.
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

Tony, I stand corrected, seems a lot higher when your under them working..
Mattro, as Tony says, inspection holes in sump pan, ( if you have later sump) will make separation a lot easier..
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

I have the car back working without pulling the gearbox. This may be a little premature since I have done about 4 miles so far.

So.. after I epoxied the plug back in I got down the road and same thing happened and I could hear the sensor hitting the teeth.

On checking the mount had come loose again. This time totally free.

I removed prop for better access and raised suspension to get a better look. I inspected the teeth and I had one bent tooth (which I managed to bend back) and the gaps between teeth were not consistent. I user the fastening end of a cable tie trimmed with the dremel to gap the teeth.

I then got the plug back into the roughly the right position, aligned by eye using the bolt holes and the cut out in the casting where the wire end of the CKP goes.. Minor adjustments on where the plug goes back in are not too easy. I used a hook with a handle to pull the plug outwards with some force.

I then drilled a hole and tapped (M5) a bolt through the casting. There is an easy to access flat part to drill through, however, this has to be at an angle (guessed) so the entry 'interferes' with the side of the plug. You can feel when you are through the alloy and hit the plug. There is a void in between the entry and the alloy wall around the plug. There looks to be about 10mm of meat in which to tap..

Next I took a stainless bolt and used a grinder to make the end into a pin with a point, leaving enough thread to engage with the tapped part. I did this as I had stopped drilling when I hit the plug so the exit hole would be smaller an the tap would not reach far enough to tap the outside wall around the plug

At this point the plug was still loose enough that I could feel when the bolt secured it tight. Small adjustments on its final position at this point were not possible so the final position ends up as a best guess. I have tried to move the plug with some force and it is well stuck. I used loctite on the bolt so hopefully it will not come adrift.

Replaced CKP with one washer added each side to space it (assuming that the plug may not have been correctly seated all round) and started - I got a tapping noise from the CKP, it was hitting the teeth. I removed the CKP took out the dremel and cut away the plastic surround of the CKP, prob about a mm each side - you can take quite a bit off without revealing the gubbins inside (The part that fits through the hole in the casting). I then drilled out the hole in the spacer and the holes in the CKP. This allows some wiggle room with the CKP in its mounting hole.

Fitted back to car, started (still some noise and with my hand of on the CKP you could feel it just hit hitting the teeth). I slackened the bolts and moved the CKP up and down between the bolt holes and into a position where it is not hitting the teeth.

Tightened up and took for a run and all good.

Will it stay this way.... Who knows..... I'll be back to let you know if it fails.

Cheers,
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

Fingers crossed you've managed to fix it, sounds like a job and a half !
 

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Re: P38 Gems CKP Crank Sensor Mount Loose - Help on a soluti

I had a scare with something similar. When I was giving my tired 4.6 some love, I changed the CPK sensor and the new one came with a much thinner washer than what was equipped on the GEMS originally. I thought to myself that is why the car was having such a bad misfire and couldn't go past 3,000 RPM. I installed the new washer on and it had the CPK touching the teeth but without me really knowing. I got all excited, cranked the car a few times hears a loud "POP" and the CPK shot straight out ruining the threads to the housing. Realizing the car would not start and the CPK just dangling, I Drank a beer, let out a few swears, ordered the part and re-tapped the housing with a new screw. So far shes sitting in using the old thicker washer and running fine with a Jerry'd Housing. Do what works! My Range was only $650 so budget is my name with my build! hope she runs well for you!
 
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