Referance sensor question?

[RSW]

I am pretty sure my referance sensor is to blame for my cars stalling and non starting problems.

When it does run a ticking can be heard, its quite loud (loud enought to be heard from 5 meters away if you listen.

when it stalls (and won't restart) the same ticking can be heard as the engine is turned - I'd put this down to a tappet but I'm not too sure now.

If I disconect the referance sensor plug and spin the engine there is no ticking at all... which is puzzeling.

My next question is: Is it the sensor that is ticking or is it an injector. Maybe with the referance sensor disconected no fuel is being injected so a possibly faulty injector is not ticking - if that makes sense?

Does anybody know enough to help me out on this one?

Many Thanks
Richard

[RSW]

Just another little detail - As i rev the engine (by hand while under the bonnet) the ticking increases in speed very much as you would expect But as the engine speed drops again the ticking stops - untill idle speed is reached again.

This all happens in a fraction of a second obviously but it does happen.

This added to my idea of it being an injector as I guess the fuel supply would be cut as I let go of the throttle.

I tried removing the electical connectors to the injectors on 4,5 and 6 one at a time as the engine was running but this made no difference to the ticking sound.

Richard

[ChrisBennet]

I've seen at least two reference or speed sensors that went south and caused intermittent no start problems. It appears to be the wire for the sensor more than the sensor itself. They sit right over a heat exchanger and eventually get cooked.

That said, I don't see how a bad sensor could cause a ticking noise. If the sensor bracket loosened, I suppose it could hit the timing teeth and make a ticking.

If you want to rule out the injectors for diagnostic purposes you can unplug the connector that drives them. The connector is on top of the "beam" that passes behind the engine as you look at the engine from the rear. It sits right behind the throttle body, between the engine and the firewall.
-Chris

[Thomas Owen]

Richard,
On your engine you have 2 sensors on the flywheel. I seriously doubt either would cause the 'ticking' sound you hear - it is most likely a tappet.
As to the stalling, however, the sensors can cause that. There is a resistance check outlined in the Bentley manual that covers both, and the cylinder head temperature (upper plug) has been replaced by a more reliable 2 wire unit. You can remove the plug on the left side of the engine and see if there are 2 pins.
If you need the resistance values send me a PM.
Good luck,

[Jeff]

Also, while you are back there check the sheathing on the sensors. Mine was cracked and falling off. If they are cracked replace them, you will be stranded if they fail and as stated by Chris it is usually the wire not the sensor.