#1

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Basic engine info:

What does the fly wheel do?

Note: This detail is for a single mass fly wheel, dual mass is a bit different.
A few things:

-It acts as the interface between the clutch and the engine
-It acts as the interface between the starter motor and the engine
-It adds momentum to the rotation of the engine (don’t worry about this bit).

Fig A
Basically the engine can never stop spinning one started, or else you ‘stall’. So when the car is actually driving :
-the engine spins the crank shaft
-the crank shaft spins the fly wheel
-the clutch is pressed against the flywheel and so spins with it
-then finally the clutch spins the gear box that transmits the drive to the wheels.

Fig B
When you change gear you have to separate the engine from the gearbox, else you get a bit crutch so:
-Pressing the clutch pedal pulls the clutch plate away from the flywheel
-the gearbox is separated from the engine allowing you to change gear.
-The engine is allowed to keep spinning.


That is one bit the fly wheel does, the second bit involves starting the car.


Fig C
-The outside of the flywheel has teeth on it.
-The starter motor has a little gear on it that meshes with the teeth on the flywheel.
-When you start the car the starter motor spins (powered by the electrical energy in the battery)
-the spinning of the starter motor turns the flywheel.
-when the fly wheel turns, the entire engine turns over.
-After a few turn overs the engine becomes self-sustaining and does not require the starter motor.

Fig D
Whilst the engine is running, or when it is off, the starter motor is not required. During this time the gear on the motor is retracted and the starter motor and flywheel are not in contact. If you can’t start the car, it may be that the starter motor is not ‘extending ’ to mesh with the flywheel. You can hit it with a hammer sometimes to get it moving as per the AA block.

Fig E
When you want to start the car, you need to get the engine moving somehow. Old cars use a handle and elbow grease, modern cars use electrical energy. When you turn the key the starter motor shoots the start motor gear (called a bendix gear) to mesh with the flywheel. Then the motor spins and starts the engine.
When the engine is running, the starter motor retracts as the engine is now self-sustaining. This is why you get a loud crunch if you turn the key to ignition whilst the engine is running. You have basically shot the bendix gear into the spinning flywheel and it is clattering against the spinning teeth unable to engage.


So in summation, the guy is basically telling you that the teeth on the flywheel are no longer there, so the starter motor cant turn the engine over. Look at a picture of a fly wheel and tell me how likely it is that a lot of the teeth have been stripper off a solid bit of metal.

#2

Blimey, TCT for that Greg - THAT'S A LOTTA INFO!! I will re-read this later tonight as I can't really do so properly at the moment.

I had a brief look into the problems we had a few days ago, and saw a lot of posts about people with Zafira's, where the flywheel was shit. Our one is a 1.9 Turbo Diesel, Manual Zafira - 2007 reg. Is this one of these "dual mass flywheel" ones or just a standard one?

TCT again for the info Greg!

#3

Not very and good description Greg

Jeg when it didn't start did it make a click sound or an awful grating sound?

#4

Originally posted by Maximus:
Jeg when it didn't start did it make a click sound or an awful grating sound?

It did fuck all. Lights lit up, no sound what-so-ever, hence the AA guy thought it was the starter motor and whacked it with a hammer. It then started. It may well have been the garage trying to pull a fast one - but the garage we took it too was in-fact, recommended by the AA guy in the first place!

#5

Don’t know if it is a dual mass or not, might be worth doing a bit of research to find out. I say this as dual mass wheels are more expensive than single mass. But normally there is a single mass wheel they can fit in place of it.

It’s a bit basic the info and anyone that know more about it that myself would blow holes in the info but I might give you some basic detail if they try and fuck you about.

#6

Nice one Greg - Muchas Gracias. I will do some reading up tonight.

#7

Any news on the motor Jeg?

#8

It has been to two garages since the guy that said it was the flywheel - both reckon there is nothing wrong with it. It looks to me like the starter motor may still be a little temperamental - but that's it. Wanker from that garage has caused us a shit load of grief we didn't need.