My daughter's Punto stopped at a set of traffic lights. The AA said that the belt has gone. After googling to this forum thought I'd give it a go after 30 years away from car DIY (Fords)
The belt is intact with no signs of missing teeth or tearing and the tensioner seems to be ok (90 degree twist method). Can they slip?
I thought it would be easy to check the timing but the modern Haynes manual misses out loads of steps for this Fiat novice.
I've been trying to get the auxiliary belts and pulleys off but noticed posts about marks through bell housing. Looking from the battery it looks like 3 or 4 triangular teeth on the housing (which one do I line up with?) Also I've seen grooves, holes and studs through the hole so which do I use? Can anyone provide a link to pictures etc
When I turned it over without the air filter box, petrol was spitting up from the injection unit. Is this normal or signs of an injector problem?

There are guides in the Cento and Punto section (and there's nowt wrong with the Haynes, either......).

If you can't get the marks to line up at TDC no1 (but they won't line up every rotation, note!), the timing has slipped. If the timing has slipped, the only sane thing to do is replace the belt. @Spitting up@ probably indicates that the timing has slipped.

fingers99 said:

There are guides in the Cento and Punto section (and there's nowt wrong with the Haynes, either......).

If you can't get the marks to line up at TDC no1 (but they won't line up every rotation, note!), the timing has slipped. If the timing has slipped, the only sane thing to do is replace the belt. @Spitting up@ probably indicates that the timing has slipped.

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Thanks. I'm new to the forum so I may be missing something obvious but I couldn't find anything in the guides that explained the view through the hole in the bell housing. Without this I can't see if the marks line up. I haven't managed to get the auxiliary belt pulley off yet because I need to buy an allen key so hoped for the other method.
I take your point about replacing the belt once I can be sure it's slipped.

Just found this link https://www.fiatforum.com/punto/249913-1-2-8v-timing-marks.html

The alternator mounting bolts will take a spanner -- 15 0r 16mm AF, IIRC.

Use the piston position method - its more accurate than the flywheel marks.

WhiteSei said:

Use the piston position method - its more accurate than the flywheel marks.

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Is that where you put a screwdriver into no1 cylinder and turn the engine until it's at its highest?

fingers99 said:

The alternator mounting bolts will take a spanner -- 15 0r 16mm AF, IIRC.

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I managed that one although the top one was a bit awkward but there's another belt to what I guess is the waterpump and its fastened with allen studs.

BTW the Haynes Manual shows 3 studs to remove the auxiliary pulley wheel but there's one right in the middle as well. Does it come off without touching that one?

It depends on the engine. HGT is at top dead centre of #1. Others are at 50% stroke using 4 equal length dowels. You'll need to research the details.

WhiteSei said:

It depends on the engine. HGT is at top dead centre of #1. Others are at 50% stroke using 4 equal length dowels. You'll need to research the details.

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Ok. Assuming it's TDC for no1 I've just checked it and it occurs at exactly the right position on the cam sprocket and the marks in the bell housing. The car was running fine just before stopping so I'm now thinking it's not a belt slip / timing.
I've checked for a spark and ok.
The only puzzling thing, (I've never worked on injector cars), the injector is mounted in the middle of the unit and seems to be squirting down onto the top of a closed throttle flap (the flap moves if I move the accelerator pedal) This seems to be why the fuel is squirting back up. I can't see how it could work unless something is supposed to let fuel through. Any ideas?

Take off the cam belt cover and look for missing teeth or cracks at the teeth bases.

I believe the 8V should be timed at 50% stroke after TDC. But others will know better than me. Don't assume this is correct.

There was a thread last week that included pictures of the timing marks.

Ok guys I give up. Thanks for all the advice. I'm as sure as I can be that it's not the belt but thinking about the noise it was making when it stopped I can see why the AA thought that. I think it involves the head - found out it's already been skimmed once and less than 30 k miles so garage job. I haven't got a compression tester or even a spark socket to reach 2 & 3 so cutting losses.
Will post again when I find out what it was for future ref.:bang:

Strange! Local family garage says £500 because timing has slipped and valves are bent. It's the 8v engine and I thought thay were all non interference. I also lined up the camshaft with the bell housing markers to check the timing. Can you spot bent valves without taking off the head?
They seemed keen to sell me a replacement car. I'd like to trust them cos I've used them for years but this doesn't make sense.

Oversight on their part probably - may have diagnosed slipped belt and assumed valve damage. Not to many non interference motors around.

The plot thickens. The engine is a non interference engine so with a bit of pressure from me the garage looked a bit harder. The valves etc are fine but the camshaft sprocket internal key to the camshaft has broken. With luck and a new sprocket it'll be back working again soon.

Sounds like the cam timing wheel wasn't tightned up and the key failed.

Fiat 8V engines are non interference. Cam belts can do what thy like without damage. BUT if its timed on the wrong stroke the cam will be 180 degs out of phase sucking though exhaust and blow out of the inlet.

This is dodgy because it can ignite fuel in the inlet manifold and literally blow it apart. So always check the timing is correct before firing up.