Cam belt unaligning self

[sam2.0 10]

I am sick and tired of setting my timing up!

 

I have set the cam cogs to be perfect, the alternator, and the cam pulley, I then get the fly wheel on the mark, ensure the belt is in the teeth on the lower cogs and proceed to put the belt around the upper pulley and then the tensioner, which I tension up and bolt down. The straight part of the belt I can only twist 90degrees.

 

I then rotate the engine over by hand (on the crank) twice, check its all aligned, which it is, so fire it up.

 

It won't fire, so line up the cam pulley, to be correct and now the fly wheel is 3 teeth out of what I set it up to be before! The belt is still tight and is still on the pulleys no problem. To add, compression is fine in all 4 cylinders, between 195 and 200.

 

Any ideas? Could it be there is some play in a pulley somewhere, so its slacking off?

[Wullie 1]

Check the crankshaft pulley is tight an properly aligned, there should be a TDC mark on it which you can compare with the flywheel mark. It should line up with a mark on the camshaft cover. Or you can use the stick down the plughole method. These have been known to loosen, damaging the keyway and allowing the pully to rotate out of alighnment.

 

I appreciate this must be really frustrating for you but is you stick to one continuos thread rather than starting new ones people will be able to follow the saga from start to finish and have a better idea of what has/hasn't been said/done. Also sticking in your location and car variety in you sig helps as well. You could be local to someone but the don't rrealise it. Sorry to sound like a teacher but only trying to be helpful.

 

Wullie

Edited March 7, 2013 by Wullie

[sam2.0 10]

The mark on the crank pulley is the small line across the pulley, which should be visible by looking down onto the pulley? I can see a marker on the cover where it should like up too.

 

I haven't yet checked the difference, if any, between the pulley and the flywheel. Next test I suppose.

[Wullie 1]

Mine is a 1.8 16v. There is a line/notch on the inside lip of the pulley. If you jack up the drivers side front wheel with the car in 5th you will be able to turn the wheel by hand while watching the crank pulley rotate. I'm not sure if the 2.0 16v has V-belts or ribbed but assume the principal will be the same. I'm sure someone else will have a more definite answer on that.

[sam2.0 10]

Mine (2.0 9a) has a toothed belt, like the pulleys.

 

I don't get the idea behind rotating the wheel, I can rotate it by the crank pulley.

 

When turning the crank over, the flywheel moves, and if I use a screwdrivers to turn the flywheel (just a few degrees to line up) it moves the crank pulley. So they seem connected.

 

I'll line up the crank mark and the flywheel tonight, turn it over and see if they still match. That'll rule out the pulley, crank or flywheel.

 

 

Any other thoughts please, so I can try a few things tonight!

[Wullie 1]

I have an aversion to turning engines by using a spanner on the crank bolt, that's all, nothing strange or sinister.

 

The timing belt runs over four pulleys. The tensioner pulley is not toothed so is irrelevant. The intermediate shaft only drives the oil pump so will not affect valve or ignition timing. This leaves the the camshaft and crank pulleys. Both are located by keyways on the shafts and pegs cast into the pulleys to lock them into position so if they are properly tightened there should theoretically be no movement. However, if a peg or keyway is damaged this will allow the sprocket to move out of sync. Given the damage that can be done if it all gets too far out my approach would be to find TDC using the rod in the plughole method, ensuring that it's on the correct stroke. When this is done compare the marks on the flywheel, crank pulley and camshafts. Any discrepancy should be apparent and investigated.

 

In your case. as the timing has apparently moved of it's own volition. Assuming you tightened the distributor before starting the engine then the culprit must be one of these pulleys. Again assuming that most of the components are exposed with you currently working on it I would remove, once again, the cam pulley and crank pulley and investigate their condition. Alternatively, and more risky, is to retime the whole shebang without doing that, tippex the position of the cam belt in relation to their location on the pulleys and anywhere else you feel relevant and try again.

 

If the crank pulley is out then valve and ignition timing will be out in relation to the rotation of the crank, result poor running and the possibility of valves and pistons becoming extremely intimate.

 

Hope this helps. It may not be everyones way of doing it and I'm sure someone more intimate with 2.0 16v's will put me right.

 

Wullie

 

PS If I remember correctly you replaced the cam pulley with a new one in another thread. Was the keyway on the camshaft OK? If so the main suspect, by elimination should be the crank pulley. Bear in mind that it may not move when turned by hand but the much higher forces generated by a running engine may do so.

 

PPS My reference to V and ribbed pulleys was to the part of the external part of the pulley that drives the altenator etc, not internal toothed part that drives the timing belt.

Edited March 7, 2013 by Wullie

[bmwcompact 10]

Firstly I am glad that your compression is OK so your valves must be undamaged.

 

Whilst Wullies analysis is spot on, I have alternate advise.

 

Try to find a forum member or someone familiar with the engine to look at it with you. You've been struggling for a while and just want it sorted. It may be that you are doing something in error that you are unable to see. Lots of us have been there-it happens.

 

I have read on this forum of crankshaft pulleys coming loose and causing a problem. Trying to remove/replace the crank pulley raises more issues for you: how to lock the crank to remove/retorque the bolt; the need for a new bolt; the fact that the pulley socket headed bolts may be chewed up and hard to remove; and the fact that the inner pulley for alternator/water pump (called a vibration damper by VW) may be seized to the actual crank pulley.

 

There must be someone around Oxford who could give you a hand!

Edited March 7, 2013 by bmwcompact