Help With Diesel RPM Sensor

[David]

Hi everyone, as the title states, I'm having a bit of trouble with my diesel rev counter & I'd appreciate some advice on it.

It has been reading low/ erratically for a few weeks & it finally died last week, which I assumed was because the sensor was too far away from the flywheel. However I had a mess around with the sensor yesterday & no matter how close I put it, there's no reading coming from the rev counter.

I've already tested for power to the clock & it's fine. The clock itself is jumping slightly when the ignition is turned on & off, which is normal, so I assume the clock itself is fine. So, in short, I believe it needs a sensor.

Now, here's where it gets difficult; Ideally, I need the type of sensor that goes into the top of the gearbox, the same as the GTi cars, because there is no cut out on the back of the gearbox & engine where it normally goes on the diesel. Access to the said hole is extremely difficult though because of the water & hydraulic pipes that are just above it.

I've previously bought a sensor, but it was around 10mm too short & wouldn't work despite it going in the hole.

Currently, it has a standard diesel sensor pushed into the hole with a piece of water pipe & a cable tie to hold it in place. It's a firm fit so won't move unintentionally, but if I could get a better fitting sensor, it'd be better. If I have to use the same type again, I will, as I know I can wiggle this type in between the water & hydraulic pipes.

Here's one sensor I've found, which I believe is most like the original, although the plug is different. I'm not worried about that as my BX lost its original plug years ago:
https://www.ebay.co.uk/itm/335329674079 ... BMwPqOk-Vj

If needed, would this be compatible with the BX? I just need to know if it's the same size & ohm rating as the original.

Alternatively, would this be suitable?: I can't see the measurements on this one, but another stated the measurements, it seemed about right. One was also listed as 'automatic only', but I don't understand why or what the difference would be.

https://www.ebay.co.uk/itm/225193636452 ... BMgqWNlOVj

Again, would this be compatible, both in size & ohm rating?

This one is like the previous one that I bought, which is too short so not suitable:
https://www.ebay.co.uk/itm/355627688837 ... R8D6jpPlYw

I've quickly measured up the car & the hole through the gearbox seems to be around 17mm wide & around 23mm deep, but the cut out on the flywheel is around another 10mm down. (I'm working from memory, so these figures won't be exact). So I think the sensor needs to be around 30mm long, assuming it'll need around a 3mm clearance for the flywheel (+ discrepancies in my memory).

Any help with this would be greatly appreciated. If anyone has any better idea of a better fitting sensor, feel free to post the links.

Thanks in advance!

[Jaba]

Here's one sensor I've found, which I believe is most like the original, although the plug is different. I'm not worried about that as my BX lost its original plug years ago:
https://www.ebay.co.uk/itm/335329674079 ... BMwPqOk-Vj

If needed, would this be compatible with the BX? I just need to know if it's the same size & ohm rating as the original.


Any help with this would be greatly appreciated. If anyone has any better idea of a better fitting sensor, feel free to post the links.

Thanks in advance!

That looks like the correct sensor for the XUD but you are fitting it into the top of the flywheel not at the usual 10 o'clock position.
Have you checked the failing sensor's resistance as this will tell you if it is faulty or if your problem lies elsewhere. I seem to remember that the sensor is a sliding fit in a holder to enable adjustment to get the minimum clearance from the flywheel. I don't know if this, the correct holder can be made to fit your block though. I might have one somewhere if you want to experiment further.

[David]

Thanks for the reply.

I’ve not had chance to look at it again over the last few weeks, but it’s sort of been working again, when I’ve driven my BX, initially it shows nothing, then it’ll suddenly jump up to 3000rpm on the clock when the engine is at tickover & it’s gone right around to 6000rpm when, in reality, the engine has been doing around 2500rpm. It’s not consistent either, other times it’s been jumping from 0-4000 regardless of how fast the engine is actually going.

I’m still convinced it’s the sensor, so I’ve ordered one of those in the link above, I’ll just have to see how looks when it arrives.

Thanks for the input about the sensor. Now that you mention it, I recall someone before saying that they’re all sliding sensors & it is just the holder that’s different.

Where does the rpm sensor usually go on the TD cars? I didn’t notice a cutout in the back of the gearbox like the NA has.

If you’ve got a picture of the correct holder for a TD car, it would be very helpful. If need be, I might get it off you if I can’t make anything else to fit.

Thanks again for the help!