Technical Cam Belt Trouble

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Technical Cam Belt Trouble

klaw

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To cut a long story short. My son was given a P Reg Punto 55 S. It's turned out to be the car from hell, after spending God know's how much to get it through it's MOT a month later the cam belt went as he turned the engine off i.e. he turned the engine off and when he tried to restart it wouldn't, the cam belt teeth had stripped

Anyway, I put it on ebay, but the buyer welshed out. But one of the emails I got about the car told me that if the cam belt goes on this type of engine then the engine's not damaged. So, I replaced the cam belt on Friday, turned the engine over and it turns over normally then sounds like it sticks, turnovers normally then sticks etc. It doesn't turnover long enough for it to fire before it stops or sticks. (keep in mind that the car has been on the driveway for 6 months)

Questions, is it true about the engine not being damaged if the cam belt goes and does it sound like a valve(s) is bent as the engine turns over normally then stops/sticks?

Any help would be greatly appreciated.
 
Thanks for that, at least I know now that I haven't got to strip the head down:) :worship:

Yep, tried jump leads and a power starter pack but both seemed as if there wasn't enough energy! Strange! Went and bought a new battery which turns the engine over a lot faster now except it doesn't tunover long enough for it to fire, seems as if it sticks.

I had an email from safeguy who said that he had the same thing and it was the starter motor sticking. Unless anyone else has any other ideas I'm going to whip the starter motor off, give it a clean-up, some WD40 and see what happens.
 
Well it maybe that when you fitted the cam belt the crank was on the wrong cycle, so when you turn the engine the crank is doing the complete opposite to what the valves are doing (maybe causing to much compression and stoping it turning over?). So take the belt off, turn the crank only 180 deg then try again...
 
Thanks, I'll try the starter motor first then I'll check the crank. When I fitted the belt No 1 piston was at TDC, I took the spark plug out and looked into the bore. I did that because I couldn't see the timing mark on the crank shaft casing. The timing mark on the camshaft was fine (as per the photo's in this forum which I found afterwards!!) and I pretty sure the crank was in the correct position too, although I do have a niggling doubt.
 
In one cycle the pistons are at TDC twice, maybe you were unlucky and got the wrong TDC time....
 
klaw said:
To cut a long story short. My son was given a P Reg Punto 55 S. It's turned out to be the car from hell, after spending God know's how much to get it through it's MOT a month later the cam belt went as he turned the engine off i.e. he turned the engine off and when he tried to restart it wouldn't, the cam belt teeth had stripped

Anyway, I put it on ebay, but the buyer welshed out. But one of the emails I got about the car told me that if the cam belt goes on this type of engine then the engine's not damaged. So, I replaced the cam belt on Friday, turned the engine over and it turns over normally then sounds like it sticks, turnovers normally then sticks etc. It doesn't turnover long enough for it to fire before it stops or sticks. (keep in mind that the car has been on the driveway for 6 months)

Questions, is it true about the engine not being damaged if the cam belt goes and does it sound like a valve(s) is bent as the engine turns over normally then stops/sticks?

Any help would be greatly appreciated.

I think that the email came from me I was Punto hunting a the time I think I remember the ad in ebay. & yes it sound like your timing is 180 degrees out - easy to do!
 
OK, this is the state of play so far. I took the spark plugs out and turned the engine over by hand just to eliminate any mechanical 'Sticking', it turned over fine.

I'm getting a spark and petrol and the starter motor seems to be turning it over OK.

With the cam pulley on the timing mark the valves on No cylinder are free, I know the crank pully is in the correct position because I made sure that No 1 cylinder was on TDC when I fitted the belt. So both cam pully and crank pully are in the correct position. But it just won't fire!

How can I tell if the cambelt is a tooth out? Or is it trial and error? Any ideas would be greatly appreciated
 
Right, the piston may have been at TDC, however in one cycle there is two TDCs, the piston will be going the wrong way for the valves. Thats why it turns freely when the spark plugs are out because there is no compression and when the plugs are in the timing is wrong so there is way to much compression which stalls the engine.

Take cam belt off, turn the crank 180 degrees/half a turn and you will see it comes back to TDC then put the belt back on.
 
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If you are at the 'wrong' tdc but correct camshaft position, one complete revolution of the crankshaft (with cambelt off) will bring it to the 'correct' tdc for that position of the camshaft. The camshaft revolves at 1/2 engine speed. I assume you have put the HT leads on their correct spark plugs. If you have had the head off did you move the pistons to de-coke them? In which case you may well have got it all out of synch.
 
OK, so what you're telling me is that if I take the cam belt of the crank, then turn the crank so that No.1 pistion goes down then comes back up again to TDC, refit the belt it should be OK?

BTW. HT leads are correct, they're numbered and I haven't had the head off.

Also, anyone know of a place for cheap spares, I need a couple of door locks with keys?

Many thanks for all your replys

Kev.
 
Took the belt off, turned the crank one full turn, put the fly wheel back with the notch matching the hole!!!!!! I never noticed that before!, put new plugs in and it FIRED UP!!!!!!! :eek:)

Thanks chaps, much appreciated
 
It is of course correct to say that a piston reaches TDC twice in a four stroke cycle; however, I think the information above is misleading in that when the cam belt is not attached, the relative positions of the cam shaft and drive shaft are no longer determined by the belt. Thus when setting up to fit a new cambelt it is only necessary to correctly position the pulley wheels on the drive shaft and the cam shaft. I have just succeeded in doing this job on my Punto 55SX. To clarify a point raised earlier in the thread, the mark on the drive shaft pulley should be set to about the 10 oclock position. For more precise positioning, I could see no clear mark on the crank case, but using the photographs available elsewhere (see link below) I placed the mark on the pulley against the apex of the angle in the metal plate which adjoins. This worked fine.

One final queary however: a friend has suggested that the belt is directional; I did note a couple of arrows on it, but the fitting instructions on the box made no reference to this (wheras great importance was placed on the tensioning of the belt - I followed the instructions, also available from this forum, and this seems to have worked fine.)

Can anyone provide advice on this?
Link to photos
https://www.fiatforum.com/punto-technical/19733-photos-timing-marks-8v-f-i-r-e-engines.html

Tensioning advice

https://www.fiatforum.com/punto-technical/2070-timing-belt-snapped.html
 
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