Crank Sensor and ECU Problems

[rood_boy]

Hi

Over the last feww months my Westie has been stalling at traffic lights and junctions every so often and needing a couple of turns to get it started.  Finally it has given up the ghost and I have no ignition.  I have changed the crank sensor as it was completely gone, the shrouding had all come away and I'm surprised it carried on for as long as it did.  The original one was a Bosch Part No. 0261210030 and I've replaced it with a sensor part no. 90451441.

Now, the starter motor turns but there is no spark or anything at the injectors.  I have a DTA E48 EXP ECU.  I have checked the continuity from the crank sensor to the ECU and that is fine.  The Crank sensor was in such a bad state that I'm sure that was the problem, and if there is a problem with the ECU now, that seems quite a coincidence.

Any help would be greatly appreciated

Chris

[Guest]

what engine is it mate?

[rood_boy]

Sorry basic information missed out.

Vauxhall 20XE. 2ltr 16v

The old favourite of many a Westfield driver

[sport 2000 Dan]

Hi is this problem since the new sensor was fitted?? or did it start then die? not sure on the part numbers cos im rubbish at that but is the new sensor the same length? ie has it got the same air gap, to check: un-plug the sensor and connect a multimeter between the two wires, if it has three then measure the resistance between them and you sould find two of them have a few hundred ohms between them .6/.7/.8 kohm, (the other wire is just a screen to counter act any interferance,therefore not actualy connected to the coil inside the sensor), anyway, volt meter between the coil wires set to AC!! then crank the engine over you should read over 0.5 of a volt, typicaly this voltage will rise well over a couple of volts as the engine turns over faster and faster.

hope this is of help, post any mor info if not

cheers.

[rood_boy]

Hi

I've checked the resistance between the ground and sensor terminals and it reads 884 ohms (0.84Kohms) so that`s alright.  

The engine originally ran before i fitted the new sensor ok til i parked it.   When i got back in and tried to start it there was no ignition.  When i fitted the new sensor there was no improvement, it didn't fire once.  I've checked with an ignition tester in line between HT leads and dizzy and ht leads and spark plugs but it doesn't light up.  I've also checked injectors with noid light set and no joy.

When you say i should be geting over 0.5 volt where is it I should be testing?

Thanks

Chris

[perksy]

Have you hooked up a Laptop and checked

the live display  

[sport 2000 Dan]

hi mate the test should be carried out between the two wires at the sensor (disconnected) or at the ECU with the ECU disconnected pm me if any probs and i will try and help you out

[melt]

In the DTA manual it mentions that you can get starting problems if you connect the VR crank sensor the wrong way round.  It suggests trying it both ways or using an oscilloscope to check out the waveform (a rising voltage is the correct one).

HTH

Mel

[sport 2000 Dan]

An osciloscope would be the best option BUT you need to know how to use one properly and get hold of a half decent one, it may say the rising voltage is the correct one but the waveform should be AC so it should rise and fall and equal amount above and below the base line which would be very difficault for a person not used to scopes to understand.

[rood_boy]

Hi

Thanks Dan I will try the voltage test tomorrow.  Probably best if I try at the sensor and also remove the ECU so I can put my probes on the connector that goes on to the ECU.  

I haven't tried swapping the wires around like the manual says for the simple reason that the car has run for 9 years with the current wiring without any probs.

Unfortunately I haven't hooked up a laptop yet as my work computer won't allow me to install the software.  Would hooking up a latop diagnose the fault straight away?  

I've never checked it through a laptop, always left that to the experts.  Maybe I should try and learn.  After all that's what makes all this fun!!

Chris

[perksy]

Unfortunately I haven't hooked up a laptop yet as my work computer won't allow me to install the software.  Would hooking up a latop diagnose the fault straight away?  

I've never checked it through a laptop, always left that to the experts.  Maybe I should try and learn.  After all that's what makes all this fun!!

Chris

You could check Engine speed on the Laptop

If the ECU isn't receiving an Engine speed input

ie it reads zero and doesn't move correctly whilst trying to start the engine

This would point to the Crank sensor

As has already been said an Osciloscope is the best way to check the sensor, but not everybody has access to one

Nothing else been disturbed during the work  

[rood_boy]

I've now tested the voltage AC at the crank sensor and the ecu end and it's reading 1.8 - 1.9V

So I think the sensor is fine, but nothing coming from the ECU in the way of a spark or at the injectors

[rood_boy]

Has anybody had this or similar problem before?

Would the first step be to connect up to a laptop to see if the ECU is registering the crank sensor?

Any help much appreciated

[RoyP]

Hi,

If your are quite sure that the sensor is a good one then my bet is that the distance is wrong from the rotor to the sensor, as mentioned by another. It is also possible that the sensor can be too close, this will mean that a flux change/field collapse will not occur meaning that you will not get a pulse out of the thing either.

My second bet is that you may well be looking in the wrong place; cos you said that the car stopped and didn't start again, that may not be the sensor at all and could be connections etc.

Problem is with the more recent electronic control systems is that you need specialist equipment and the skills to use them to find the problem. Knowing the problem is probably 80% towards solving it. You sure you're looking in the right place, blaming the sensor?  

Roy

[rood_boy]

I'm pretty sure the sensor was faulty.  The shrouding had completely broken away around the sensor and there was no resistance reading between the sensor terminal and the ground terminal.  Also, the actual sensor part that sits inside the block was distorted.  

When comparing the size of the sensors. they are exactly the same size and shape etc. so the distance should be the same.

Any suggestions of what the problem could be if it's not the sensor?

The thing is that the problem started about a year ago and slowly got worse.  Rather than an electrical fault or a fault in the ECU which I presume would happen instantly i.e. PCB problem or loose wire.