Hello everyone.

I am wondering if any one can shed some light on a self-inflicted problem.

I am currently replacing a gearbox on my Vauxhall Vivaro 1.9 DTI 2002 plated van and following a CD reference manual used within Vauxhall (or so I am told)?

To cut to the case! I removed the flywheel to replace the crankshaft seal, as there was evidence of an oil leak from behind it. I followed the instructions to the “said” manual and reassembled the flywheel back onto the crankshaft.

However now the gearbox has been returned. I have noticed there is a sensor on the front of the gearbox housing that directly monitors the side of the flywheel.
What I can gather from my manual this seems to be called the following names. Engine speed sensor/crankshaft impulse sensor /crankshaft position sensor or B34 on the schematics’/wiring diagrams.

I am now getting a little worried, as I did not mark up the flywheel up. Can any one tell me if this sensor does? Does it sense the crank speed or is it used for crank positioning?

If it is the latter how I can check to make sure the crank positioning is correct to the sensor/engine?

The manual went into great detail about marking the pressure plate up with the flywheel and even replacing the crankshaft to flywheel bolts and torque settings etc but no mention of marking up the position of the flywheel to the crankshaft. Which gave me the impression at the time it was a speed sensor.

Unfortunately I followed it to the letter and now getting a really bad feeling. If I do refit the gearbox the engine may not start due to an out of align flywheel and the whole lot will have to be taken back out! Am I being a drama queen?

There is a sensor on the cam on my model.

If any one has any advise or information on my dilemma?

It would so much appreciated if you could spare a little time for a reply.

Thank you in advance Paul

Paul, February 2010

No prob the flywheel bolts only go on one way the right way

Kevin, July 2012

Hi.. the sensor mentioned ie crankshaft is a impulse sensor wich counts the teeth around the flywheel there will be a refference mark/ tooth gap on the ringgear and using that as a timing refference supplies the engine ecu with a speed signal..the camshaft sensor at the top behind the rocker cover t/ belt end picks up position of no1 /4 cyls.for injection position,the 2 sensors correlate signals to engine ecu.. the flywheel position? may be it will only fit correct when all bolt holes align..the ring gear position ..doesnt matter, only refference mark..

Dave, March 2010

Hi Justin

After removing the flywheel I found that the oil leek was coming from the sump gasket that travelled behind the flywheel. Seeing I brought the crank seal and being non refundable because it was under £20 from the main dealers I fitted it any way.

I will replace the sump gasket at a later date, as all bolts are accessible from below and it should be easy enough to do once everything is back together. Mind you these vans are a complete pig to work on and that’s putting it nicely.

As the sump gasket ran behind the flywheel it did look like the main seal was leaking before and after the gearbox was removed

However never heard it being a common problem like the boxes, pumps , looms etc and many more lol

I don’t know if that’s any help?

paul, February 2010

Hi Paul did changing the crank oil seal cure your leak the reason i say this is i have just paid to have the seal changed on my reno trafic and its come back leaking as bad as ever the mechanic said the leaking seal had marked/polished the crank and this is why the new seal is not working only cure is a new crank also said this is a common problem with vivaro/trafic/primastar ?

Justin, February 2010

glad we sorted that one out!

me, February 2010

Hello again

I would like to thank every one for all the helpful and interesting replies.

As an update. I removed the flywheel today, rotated and tried to reassemble .Yep the flywheel only can go in one position or the fixing holes are out.

Dooh…

I think I chosen the easer of the two options Reading the cam belt marking and working out the sensor position seamed a little like hard work due to bracing the engine safely, as the top engine mount needed to be removed leaving only one mounting supporting plus two unstable axel stands

I obviously got lucky and found the correct position straight away.

What also through me, was cleaning the holes outs while the flywheel was held on with the one old bolt, as the treads where a little tight for me. What also didn’t help was the poor lighting conditions I have been working in.

I then felt later after reading the replies that I might have re-taped the holes as well as the flywheel if the offset wasn’t that noticeable .If you get my drift?

Yep, all very flappy.

I have to make an confession I am not userly this bad but I have gave up smoking on the 17-01-10 from about 20-30 a day and over the last week or so I am finding my self getting very stressed with a over questioning mind that seems to be looking for conundrums in absolutely anything or nothing.

I sure it will pass.

And, Yep you are right…. If the e.c.u does not see this pulse correctly it will not allow the pump to fuel the engine via the injectors.

Many thanks and kind regards

Paul, February 2010

If could be just reading pulse from the rotating ring that it is monitoring, I have changed my ECU on my race car and they welded on a flywheel ring wheel 90 teeth with 2 missing. The ECU can see 88 pulse in a row and then a gap so it thus knows the RPM, it doesn't matter where (in my case) the ring is welded on and the firing is another issue for the ECU, it just needed initially to know the RPM and when the wheel have completed a full rotation (missing teeth) - Once this reference was known the next thing was to work out TDC in relation to the ring.

In summary, it's probably just measuring the rotating speed so I wouldn't worry where it is.

Justin Smith, February 2010

unless you just got lucky first time? or there may be a sensor by crankshaft pulley too? .......

me, February 2010

This may be true but the 7 bolts did seem very symmetrical to the centre of the crank shaft and no locating pins etc where present?

paul, February 2010

on most cars you can only fit flywheel on one way as other ways the bolt holes dont line up. unless someone can tell me different......

yeah, February 2010