XUD7/9 interchangeability

[morningglory]

Hi,

The rev counter on my BX TZD is intermittent and jumpy which I put down to a knackered crankshaft pulse sensor. Does anyone know if the sensor from a XUD9 will work on my XUD7? I can't find a sensor to buy or even a part number specifically for the XUD7 engine.

Thanks!

[elma]

All my PSA diesels have used the same one but I've never had a bx.
They often just need a clean and reinstalling a little more pushed in than before to restore function.
I push them in until they stop then back out about 1mm.
The bx may be different though, mine were all flywheel sensors for the rev counter.

[white exec]

These sensors have a magnetic tip. Check that there is no metal swarf/debris stuck to it - it wrecks their action.
DC resistance (sensor disconnected) will probably show up as something like 1000-2000 ohms. They're fairly similar to ABS sensors. If open circuit or very high resistance, or low resistance, sensor is likely dud.

Check (if you can) that the gap between the sensor tip and whatever it is sensing (flywheel peg, slot, teeth...) is tiny - typically 1mm; the smaller the better for a good signal from the sensor.

You may be able to check the sensor's action by removing it from its hole/slot, switching on the IGN, and rotating something toothed and steel close to its tip. Cogwheel in an electric drill, or an old-fashioned hand-drill gearwheel would do.

Check connections at the sensor are clean and good and cabling not damaged.. The signal from these devices is miniscule.

[Pug_XUD_KeenAmateur]

I've got a number of XUD9 rev counter sensors, some acquired from scrappers, one bought brand new; in the course of attempting to fix my own tacho.

If you want to compare sizes, connectors etc, with the one you have fitted on your XUD7; I'm happy to put the micrometer on it and/or supply pix.

Ultimately, in my case (Pug 405), it turned out to be rev counter itself, which had never worked at all in my ownership of the car: I got around to 'winding forward' the mileage and replacing the instrument panel quite recently.

[xsaras4ever]

Hello , here is the BX under-bonnet sensor parts list. Does the Rev-counter use part 2 or part 4 ?

https://imgur.com/a/lAKsG

[Peter.N.]

There is a 2 pin plug on the sensor lead at the flywheel end of the cylinder head which can develop a poor connection.

Peter

[white exec]

It'll be part #4.

[morningglory]

Hi all. thanks for your thoughts.

I've tried fettling and reinstalling etc. and think I need a new one. It looks like #2 in the above diagram, with the same mount, exactly the same look and spec as both of these:

for Pug 405 XUD9
http://www.ebay.co.uk/itm/Crank-Shaft-S ... Swal5YD73w

for Citroen C15 XUD7
http://www.ebay.co.uk/itm/Crank-Shaft-S ... Sw44BYD7oQ

I don't see why all the slightly different incarnations of the XUD would have different sensors, but it seems they do have different part numbers. Tempted to just buy one and hope it'll work but I'm going to ask where I can first.

[xantia_v6]

It is my understanding that the TDC sensor (#2) is only fitted with electronically controlled pumps, and that a speed sensor (#4) is fitted in either case and would be what drives the tachometer.

[white exec]

Engine speed sensor must be the tacho driver (#4).
Road speed is sensed (for the speedometer) from the gearbox final drive.

[elma]

Yes 4 is the same one as a Xantia and a 306 have for the rev gauge. I used a 306 one in a Xantia so I think they are all interchangeable. Only difference was a longer cable but that wasn't a problem.

[Pug_XUD_KeenAmateur]

cor strewth, they're pricey aren't they !! I think I paid about a tenner for my new one and peanuts for the s'h ones.

If you want to pm me your address I'll stick one of my s'h ones in the post, assuming you're happy to take the chance on fitting it and finding it's duff

Toss up which way to get at it, but from memory, easiest access is from underneath on my 405.

[morningglory]

Ta for the offer! PM/email sent.

Easy enough to get at underneath as it sits at the bottom of the crankcase.

[morningglory]

Thanks very much KeenAmateur!Just got it fitted.

Well the rev counter is definitely driven by the top dead centre sensor i.e. #2 on that diagram from the Citroen service website, and as I thought, it appears a sensor from a Pug XUD9 is exactly the same as a Cit XUD7.

[white exec]

Well, well.
I take it the tacho is now working?
So I wonder what #4 Engine Speed Sensor is feeding?

Edit:
I've just managed to find a BX turbo diesel circuit diagram (old Haynes XUD book), and it does show rev counter being triggered by the TDC sensor. Can't find any diagram reference to Engine Speed Sensor, so still puzzled over that. Sorry to mislead above.