Diesel rev counter

Post by **CitroJim** » 11 Sep 2009, 19:20

Hi Colin,

I had the needle lift sensor injector on my 2.1TD fail back along. It did not affect the tacho.

It's more likely it's the TDC sensor that's not playing...

colinxm · Post by **colinxm** » 11 Sep 2009, 19:38

That Jim, is exactly what I wanted to hear ! you're a gent

Now, anyone got a spare TDC sensor they wouldn't mind parting with

Have a great weekend everyone, Colin.P

Post by **Peter.N.** » 11 Sep 2009, 21:27

Its often a problem with the two pin plug on the end of the cylinder head (if you can find it) - remove a few pipes.

colinxm · Post by **colinxm** » 12 Sep 2009, 19:04

Right then, I've had a poke around and the rev counter now works - whoohoo ! problem is that as soon as the engine goes even slightly above 3000rpm the rev counter dies and stays dead until the engine is switched off and restarted... It does this when driving and also when stationary, blipping the throttle also kills it

Anyone any ideas ?

Peter, mine has a three pin plug to the tdc sensor, not that I'm one to brag

Colin.P

Post by **Peter.N.** » 12 Sep 2009, 20:35

It still sounds like a bad connection, if the plug is OK it could be in the sensor. Try measuring the resistance of the coil, it will be on two of those pins, see if the reading remains constant, don't know what the resistance should be, probably about 1-2K ohms. You can connect the meter across the coil on AC Volts and watch the reading as you increase engine speed, if the sensor is faulty the voltage will drop to nothing at about 3000 rpm, if it doesn't the fault must be elswhere.

Peter

colinxm · Post by **colinxm** » 14 Sep 2009, 18:58

Thanks for that Peter but I've given up and refitted the older Bosch wiring loom again. I'm going to pull the clocks out next and compare the connections to those on a set of clocks previously fitted to a series one car, maybe then I can sort something out - perhaps the wiring to the connectors changed slightly between the two series cars.

Cheers Colin.P

colinxm · Post by **colinxm** » 15 Sep 2009, 19:39

One step closer... although the pcb's are vastly different between the series one and two instrument sets the same pathways between the rev counter and the multiplugs are used, the series two even has the cutouts and connections for the turbo pressure dial in place. I thought this was only installed on the series one's.

So now I'll be digging out of the loft the "under dash" wiring loom that was fitted to the series one car to see where everything connects to the multiplug to the engine wiring harness and then compare the current loom to see where the connection is missing.
I'll even have a go at getting the turbo dial to work and retro fit it for fun

Colin.P

colinxm · Post by **colinxm** » 18 Sep 2009, 19:15

Success ! of sorts... I've installed the missing wiring and now, after much bodging I've got a working rev counter, problem is - it reads twice as high as it should

Colin.P

Post by **Peter.N.** » 18 Sep 2009, 20:50

Sounds odd, should only get one pulse per revolution, do you still have the ECU connected? if so something may be doubling the frequency. I think it could possibly be caused by a loose contact somewhere, is the error constant?

Peter

colinxm · Post by **colinxm** » 22 Sep 2009, 19:08

Hi Peter, sorry for the late reply - I've been playing some more

The error is indeed constant and the ecu is removed, in fact, with the wiring that I've added the system should be identical to that on a fully mechanical setup.

Here's what I've found:

The original (EPIC) rev counter doesn't work at all unless I replace it's own small pcb with that from an earlier model and then it reads double.

An earlier rev counter will work with both the original (EPIC) main instrument panel pcb and also that of an earlier version, again it reads double.

The only things now original from the EPIC setup are the flywheel and the TDC sensor... surely the flywheel for the EPIC setup wouldn't have two triggers for the TDC sensor mounted at 180 degrees to each other ?

Here's another thing, the ribbon cable fitting to connect the rev counter to the main instrument panel pcb are subtly different between the two models which meant some fiddling and swapping with the soldering iron to get an earlier pcb to fit... why did they have to fiddle and change EVERYTHING between the two models (rant rant)

That's it for now, Colin.P

Post by **Peter.N.** » 22 Sep 2009, 21:23

Hi Colin

I'm stumped. The only thing you can do really is to connect an osciloscope to the output of the sensor and chek that the output frequency corresponds to the engine revs, if the frequency is double I can only think that you have a blob of something, or some damage on the flywheel, or that the flywheel is different on the EPIC. Still, it should be fun showing your 8,000 rpm diesel engine to your friends.

Peter

Xaccers · Post by **Xaccers** » 22 Sep 2009, 22:55

At least it should make the smoke test during the MoT safer for the cam belt

Post by **Peter.N.** » 22 Sep 2009, 23:28

colinxm · Post by **colinxm** » 23 Sep 2009, 04:36

You're all heart guys

Colin.P