WTF just happened? - UPDATE

robin · Post by **robin** » Tue Jun 19, 2007 10:45 am

OK, so the fuel pump primes, and the engine cranks but it doesn't start - is that where we are at?

Cheers,
Robin

ninja · Post by **ninja** » Tue Jun 19, 2007 11:00 am

yeah that's where we're at robin mate.

turn key

fuel pump primes and the stack lights up

the engine cranks but doesn't catch.

can't hear the AICV doing anything thought when i turn the key back to the off position but this is a new AICV so i would guess it's ok

ninja

mac · Post by **mac** » Tue Jun 19, 2007 11:16 am

Loose Crank position sensor?

Faulty cam position sensor (shouldn't cause this failure as it's supposed to go to batched injection) but could be a possibility.

Mac

Brigita · Post by **Brigita** » Tue Jun 19, 2007 11:50 am

I just had my Crankshaft sensor changed the other day as i was having similar problems... it's working fine now!

It was priming, cranking, firing but then dying.... not sure if these are exactly what's happening with yours... but might be an idea to check the camshaft and crankshaft sensors.

B

Ps - what year is your S2??

ninja · Post by **ninja** » Tue Jun 19, 2007 12:10 pm

it's a 2001 S2

hope this relay works - otherwise it sounds like i'm going to be chasing the fault around the engine

ninja

Brigita · Post by **Brigita** » Tue Jun 19, 2007 1:58 pm

Thats what mine is - might be a common fault.... i'd honestly get the Crankshaft Sensor checked....

B

robin · Post by **robin** » Tue Jun 19, 2007 2:01 pm

The manual is incorrect - it says that the ECU will revert to batched injection when the cam ps fails, but it doesn't - it just doesn't start. If the cam ps fails while the engine is running, you will get a MIL, but it doesn't revert to batched because it knows which cycle it's on anyway (IYSWIM).

The crank or cam position sensor could account for this.

I would swap with some known good ones (the cam ps is easier to change than the crank ps) - sounds like Mandy's S2 might be the donor ...

Cheers,
Robin

mac · Post by **mac** » Tue Jun 19, 2007 2:38 pm

Could be - the only wee problem is that Mandy's has the MIL light on. I'd wager money on it being the post cat 02 sensor which has been pretty much redundant since fitting the PTP kit and has only recently been thrust back into action.

Mac

ninja · Post by **ninja** » Wed Jun 20, 2007 4:07 pm

well as i'm sure mac has said it wasn't the relay, car still no workie!!

on the upside i now have a spare relay

ninja

robin · Post by **robin** » Wed Jun 20, 2007 6:42 pm

Mr AndyG just listed an S2 cam position sensor on the classifieds and I think I have a spare crank position sensor somewhere.

It's easy enough to test both of them now that you have a hard failure - Brigita can dig out the email I sent her on that subject recently perhaps?

The same procedure applies to both sensors, though you should expect 30x the frequency from the crank position sensor.

Cheers
Robin

mac · Post by **mac** » Wed Jun 20, 2007 6:59 pm

I was going to go over on Saturday afternoon and swap over bits

Mac

Brigita · Post by **Brigita** » Thu Jun 21, 2007 8:54 am

No worries... here you go:

My money really is on the Cam Position Sensor though there is a tale that there is a wiring loom that can run too close to the cylinder head and fail due to the insulation melting; I doubt that's the case.

If you're handy with a multimeter you can actually diagnose this yourself when it fails; and you can practice first when it's working to make sure you know what it should like when it's working.

Multimeters are cheap from places like Maplins - ideally get one that measures frequency (often indicated by one or more positions on the center rotary switch labelled as "Hz" or a square wave squiggle (__|--|__) or the word FREQ or FREQUENCY). Sometimes you get so-called automotive multimeters in which case they will measure RPM instead of HZ, but it's all the same. If you really cannot get one that measures frequency, let me know, because it can be done using the AC mode as well, but that's not as nice.

Now, disconnect the Cam Position Sensor - it's the lead that comes out of the top engine cover on the front left (looking from behind the car). It runs for a couple of inches into a connector plug that is mounted on a bracket on the side of the cylinder head. If you split open this connector there will be two terminals. Stick the multimeter leads into the terminals on the side of the connector that leads back into the engine (i.e. the side that runs back to the sensor). Now get someone to crank the engine for you - you should see something like 100RPM (aka 1.6Hz) - to be honest it doesn't matter what you see, the point it take a note of it.

Now reconnect all, put the meter in the boot and wait for it to fail again. When it fails, whip out the meter and repeat the test. If you see the same frequency as before, the fault is not the sensor. If you see no frequency at all or a random jerky pattern then the sensor is gubbed and needs to be replaced.

Good luck!

B

Rich H · Post by **Rich H** » Thu Jun 21, 2007 9:44 am

How can you use the AC mode? Would be a useful feature...

ninja · Post by **ninja** » Thu Jun 21, 2007 4:44 pm

Brigita wrote:No worries... here you go:

My money really is on the Cam Position Sensor though there is a tale that there is a wiring loom that can run too close to the cylinder head and fail due to the insulation melting; I doubt that's the case.

If you're handy with a multimeter you can actually diagnose this yourself when it fails; and you can practice first when it's working to make sure you know what it should like when it's working.

Multimeters are cheap from places like Maplins - ideally get one that measures frequency (often indicated by one or more positions on the center rotary switch labelled as "Hz" or a square wave squiggle (__|--|__) or the word FREQ or FREQUENCY). Sometimes you get so-called automotive multimeters in which case they will measure RPM instead of HZ, but it's all the same. If you really cannot get one that measures frequency, let me know, because it can be done using the AC mode as well, but that's not as nice.

Now, disconnect the Cam Position Sensor - it's the lead that comes out of the top engine cover on the front left (looking from behind the car). It runs for a couple of inches into a connector plug that is mounted on a bracket on the side of the cylinder head. If you split open this connector there will be two terminals. Stick the multimeter leads into the terminals on the side of the connector that leads back into the engine (i.e. the side that runs back to the sensor). Now get someone to crank the engine for you - you should see something like 100RPM (aka 1.6Hz) - to be honest it doesn't matter what you see, the point it take a note of it.

Now reconnect all, put the meter in the boot and wait for it to fail again. When it fails, whip out the meter and repeat the test. If you see the same frequency as before, the fault is not the sensor. If you see no frequency at all or a random jerky pattern then the sensor is gubbed and needs to be replaced.

Good luck!

B

the car's not working at all so i should expect a jerky pattern or nothing at all then?

i'll try this tonight

if this doesn't identify the fault i'll need to wait for supermac to turn up at the weekend!!

ninja

robin · Post by **robin** » Thu Jun 21, 2007 5:02 pm

Well, you can use AC voltage mode as the sensor is producing an AC signal, after all, but the result will be very dependent on the filtering on the input and the sampling rate of the meter's analog-to-digital converter - a modern meter might well be able to track a 1HZ square wave signal in DC mode (i.e. you might see an alternating 0/1/0/1/0/1 pattern).

So to make use of AC mode you would need to attach to a known working sensor and see what it reads and write that down somewhere for future reference.

Cheers,
Robin