Diesel Rev Counter not working

[mat_fenwick]

Oooh, good point mate. Your memory is obviously better than mine!

[electrokid]

It certainly is... While you've got the engine out to show Adam the sensor wire - you might as well put a new clutch in

My only contribution to this thread is... while I had an instrument pod from a 1.6i on the test bench I was driving power from a 13.8v supply as standard and the 'sensor signal' from an oscillator - the oscillator output needed to be surprisingly high - some 20v RMS.

[docchevron]

I imagine that sort of output would kill a diesel rev counter dead!
The petrol unit takes it's signal off the coil, thats a tad harder to do on a diesel!

[electrokid]

I imagine that sort of output would kill a diesel rev counter dead!

I think you are right - I did put a small - 1K I think - resistor in series with the signal for safety - the rev counter was surprisingly noisey when operating ! I'll look into the signal from the sensor on the diesel sometime.

[Way2go]

- the rev counter was surprisingly noisey when operating !

Surely this is because the rev counter circuitry is expecting positive going pulses only, yet you are feeding it RMS (sine wave?) which is negative going as well as positive going. This also probably explains why you were cranking it to 20volts for a result as the positive going part would therefore only be 10v ?

'sensor signal' from an oscillator - the oscillator output needed to be surprisingly high - some 20v RMS.

[adamskibx]

Aha - Much appreciate you taking the engine out to show me. You really should have just told me to take the engine out of mine you know

If I can't find it now, I will have to sell the BX and declare myself incapable of old Citroen ownership

[electrokid]

Surely this is because the rev counter circuitry is expecting positive going pulses only, yet you are feeding it RMS (sine wave?) which is negative going as well as positive going. This also probably explains why you were cranking it to 20volts for a result as the positive going part would therefore only be 10v ?

Yes - you're right of course - I can't quite remember how I drove it - I'm sure I used some kind of blocking circuit but not sure about offsetting - can't remember - the oscillator has a zero offset control as well and I might have used that - I just remember it was higher than I expected and it was around 20v. 20v RMS is around 28v peak - 56v peak to peak - so the positive going part was around 28v - but as you say - sine wave not pulse - connected to the coil 'primary' it would be seeing the 'back emf' as the field collapses which is around a 200v pulse. I'll be looking at it again in a few weeks time - I'll try to take better notes next time

[scarecrow]

Just been to the stealers and they couldn't find the engine speed sensor on their parts database. They are available for the zx and xantia, but I wasn't willing to stump £30 (non-refundable) on the off chance it might work! Ill have to do some scavenging.

[Oscar]

It's the same sensor for a Peugeot engine, I think.

[mat_fenwick]

Looking back through my receipts, the part number for the sensor is KL591875, and it cost £15.27 + VAT in 2004. CBA syndrome I reckon...

[scarecrow]

Looking back through my receipts, the part number for the sensor is KL591875, and it cost £15.27 + VAT in 2004. CBA syndrome I reckon...

Normally I'd agree with you over the CBA syndrome, but the guy spent a good half hour looking at his parts database for me.

I'll thought Peugeot too, Oscar

One interesting thing I learnt is that the son of the original proprietor of this particular dealer possibly has an F Reg one owner GTI squirrelled away somewhere. He did say it was a valver, but they didn't come along until later did they? I could be tempted by a valver as an occasional car... if it was really nice (and cheap).

[Brian]

If you can't get the proper sensor, the TDC sensor on non rev counter diesel engines will work..

The resistance is different though..

[scarecrow]

If you can't get the proper sensor, the TDC sensor on non rev counter diesel engines will work..

The resistance is different though..

I wondered what the parts guy was talking about when he started mumbling about how they used to call it the TDC sensor in his day. I'm afraid I was at nodding stage by then and looking for a way out

[philhod]

There was none on my old 87 RD either Doc. That's why when I stuck it in the Meteor, it ended up with no tacho.. ..or is that something Mexican, to eat.

[kiwi]

Since I got my TXD back from having a clutch fitted the rev counter does not work at all. I noted green corrossion on the plug connector and gave that a spray. I also noted what doc said about pushing closer to the flywheel? Is that a potential consideration given the gearbox has been off? If not will have to hunt a new sensor I guess.