300tdi crank sensor

[Steve_D]

Hi
Does a 300tdi use the same crank sensor to drive both the ECU and the Tacho?

My tacho has become very erratic if not dead but the engine runs fine so either they have different sensors or it is the tacho itself.

Thanks
Steve

[Texpis]

Hmm I believe you think that the 300 tdi is more complicated than it is, I'm not a big diesel fan but I believe the tacho gets its pulse from the alternator check th small connection.

Mick

[camel_landy]

The 300TDi is mechanical... No crank sensor!!

The rev counter is driven from the alternator. The speedo is driven from the back of the gearbox.

M

[Steve_D]

Thanks guys I'll go looking for a loose connection. I say loose as the problem gets worse as the engine gets hotter so a 'dry joint' type connection could be the problem.

Steve

[camel_landy]

There's a fair chance it could also be a dodgy earth... Especially as it happens when warm.

M

[paintman]

Don't forget to check the belt tension.
If the tacho is erratic at idle - sometimes dropping to zero - then it could be the belt.

[Autolycus]

Doesn't it depend on which version of the 300tdi the OP has? In Discoveries, for instance, Electronic Diesel Control (EDC) came in for the 1996my for automatics, and these have fuel, air, and coolant temperature sensors, airflow, engine speed, boost pressure, road speed, "throttle" position, and brake pedal sensors, all feeding the EDC brain.

Which is why I'm looking for a pre-96my Discovery, and ideally a 200tdi - really mechanical!

Kevin

[camel_landy]

Autolycus said:

Doesn't it depend on which version of the 300tdi the OP has? In Discoveries, for instance, Electronic Diesel Control (EDC) came in for the 1996my for automatics, and these have fuel, air, and coolant temperature sensors, airflow, engine speed, boost pressure, road speed, "throttle" position, and brake pedal sensors, all feeding the EDC brain.

Which is why I'm looking for a pre-96my Discovery, and ideally a 200tdi - really mechanical!

Kevin

It's still the same mechanical injector pump though...

I can't remember exactly what all the bit & bobs did but there's something in the back of my mind saying those bits were more for the EGR.

M

[Autolycus]

camel_landy said:

It's still the same mechanical injector pump though...

I can't remember exactly what all the bit & bobs did but there's something in the back of my mind saying those bits were more for the EGR.

M

Afraid not. The first 300 tdi Discoveries had an electronically-controlled EGR valve, and the pump had a TPS mounted on it, but the EDC cars used a very different Bosch pump and one special injector, now, I have read, no longer fully supported by Bosch. I believe it also means that the immobiliser, cause of so much trouble in the last 20 years of Solihull's finest, cannot be defeated by a couple of bits of cable and four croc clips.

It would probably defeat the average car thief if the stop control was still a bit of bent wire somewhere under the dash. Certainly (briefly) defeated me often enough with my MF135.

Kevin

Edited by Autolycus on Wednesday 30th September 21:00

[camel_landy]

Hmmm... Just done a bit of digging. It does have a different setup but on the face of it, the body of the pump looks the same but with a different mechanism on the top end.

Either way, we're starting to get a little OT here.

M

[Steve_D]

Just to round things off and issue many thanks to all.
A clean and crimp of the connection on the alternator has fixed it nicely. Still a bit erratic but then it always was.

Steve