Vauxhall Owners Network Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
682 Posts
Discussion Starter #1
:shame: Bear with me folks, I'm getting a bit long in the tooth but................

What exactly does a cam. sensor do?
 

·
Premium Member
Joined
·
7,328 Posts
The crank sensor measures the position of the crank shaft, the cam sensor mesures the position of the cam shaft.

The crank sensor is unable to work out by itself where TDC of cylinder one is either on the compression or exhaust stroke, as it needs to measure a 720 degree rotation of the engine to get to TDC. so the signal from the crank and cam sensors are combined to give this measurement.

Am I right?


Dan.
 

·
Premium Member
Joined
·
7,328 Posts
markjay said:
As far as I am aware, not all Omegas actually have a cam sensor - apparently some do and some don't.
Possibly. if the dispac fires on both cylinders at TDC at the same time (one spark will be wasted) then only the signal from the crank is needed
 

·
Registered
Joined
·
682 Posts
Discussion Starter #5
So, if has happened to my car, occasionaly not firing on first turn, would this be caused by a faulty cam sensor not sending a signal or sending an incorrect signal?

Just trying to understand the problem. I suppose I should have asked the dealer, but didn't think at the time.
 

·
Omega Tank Commander
Joined
·
7,722 Posts
danuk said:
Possibly. if the dispac fires on both cylinders at TDC at the same time (one spark will be wasted) then only the signal from the crank is needed


All the Omegas have them.

Its not essential to the DIS pack as it uses a wasted spark system, the later 2.6, 3.2 and 2.2 have a coil per plug system so they require it more (although they can fire two plugs at once as part of a limp home program).

A key requirement is to support the sequential fuel injection as it allows the ECU to calculate which cylinder is on the inlet stroke. Again a limp home mode can be used where the injectors are fired in banks if the sensor fails.
 

·
Registered
Joined
·
682 Posts
Discussion Starter #7
Marks DTM Calib said:
All the Omegas have them.

Its not essential to the DIS pack as it uses a wasted spark system, the later 2.6, 3.2 and 2.2 have a coil per plug system so they require it more (although they can fire two plugs at once as part of a limp home program).

A key requirement is to support the sequential fuel injection as it allows the ECU to calculate which cylinder is on the inlet stroke. Again a limp home mode can be used where the injectors are fired in banks if the sensor fails.
I think I understand that, so if the injectors were fired in banks, could that cause the engine not to fire on first turn?
 

·
Omega Tank Commander
Joined
·
7,722 Posts
Its hard to know what has been implimented on the later ECU software. In theory it should be able to start on the crank sensor alone but you know how lazy these software engineers can be.... (I do, I have to project manage them, they constantly moan, its to hard and you don't undertsand...it will take 4 weeks etc etc).

I suspect an immobiliser fault or similar....
 

·
Registered
Joined
·
682 Posts
Discussion Starter #9
Marks DTM Calib said:
Its hard to know what has been implimented on the later ECU software. In theory it should be able to start on the crank sensor alone but you know how lazy these software engineers can be.... (I do, I have to project manage them, they constantly moan, its to hard and you don't undertsand...it will take 4 weeks etc etc).

I suspect an immobiliser fault or similar....
Thanks Mark, I do understand, I used to manage a software team myself.

Time will tell if the problem is going to re-occur.
 

·
Registered
Joined
·
203 Posts
Said before on my Omega the spanner light would come and stay on even if it started 1st time or not. tech2 diagnosed it was the cam-sensor so it was re-placed, this is when the next problem started, now the spanner light only comes on if the engine doesn't start 1st turnover, and gos out after re-starting ( always fires 1st time if i stop & re-start) was told tech2 has to delete the old fault's and re-program the ecu. just got to Waite till mate can get round with the tech2 :cry: whilst on the subject what is the difference with the spanner in car light, and the engine warning light ( this one always gos out after stating) the manual says they are both Engine electronics & Immobilizer ?
 

·
Registered
Joined
·
203 Posts
markjay said:
But - surely a cam sensor problem would show as an error code on the ECU?

tech2 handhold shows fault: cam censor. I watched as he doing it, I was totally surprised at the info tech2 to comes up with.
 

·
Premium Member
Joined
·
666 Posts
The early fuel injection engines like the 8 valve 2.0L had none sequential fuel injection - all the injectors opened once per crankshaft rotation.
The X20XEV - the 16 valve engine - had sequential fuel injection - by using a cam sensor - the ecu could tell which cylinder was at TDC - (as the camshafts run at half crank speed) - so once it becomes in line with a lug on the cam gear it knows to open No 1 injector - it is then redundant as the ecu knows the firing order 1-3-4-2 for the 4 cylinder & 123456 for the V6 (yes I know they said years ago that couldn't be done)

The X20Xev has an advantage of using either pulse pick up (cam or crank) if one fails - although it will limit rpm's to 4k.

If your timing goes out (belt stretches)it will throw up a fault code though. infact as it uses a Seimens system called simtec - its renowned for throwing up fault codes.

Auto Addict said:
:shame: Bear with me folks, I'm getting a bit long in the tooth but................

What exactly does a cam. sensor do?
 
T

·
Guest
Joined
·
0 Posts
RoVic said:
whilst on the subject what is the difference with the spanner in car light, and the engine warning light ( this one always gos out after stating) the manual says they are both Engine electronics & Immobilizer ?
If its the same as on mine and I think it should be, both facelift 2.2's, then the light with the piccy of the engine on it, means emissions problem, only serious if it flashes when driving. (mine comes on randomly, but then mine has been converted to lpg and i think is just confusing the sensors a tad)
The one with the spanner sticking through the roof means the ecu has detected a fault.
 

·
Registered
Joined
·
682 Posts
Discussion Starter #15
Marks DTM Calib said:
Its hard to know what has been implimented on the later ECU software. In theory it should be able to start on the crank sensor alone but you know how lazy these software engineers can be.... (I do, I have to project manage them, they constantly moan, its to hard and you don't undertsand...it will take 4 weeks etc etc).

I suspect an immobiliser fault or similar....
Mark - I don't like putting people on the spot but just to put you on the spot - if it was your car what would your plan of action be please?
 
1 - 15 of 15 Posts
Top