question for you engine experts..?

[euro_urs4]

have a question if this is a problem with starting my car, i was double checking the flywheel pin, camshaft sensor, and timing on the motor and everything is good, however what came across my mind was that the way the motor works is that for every revolution that the cam pulley does the crank does 2 turns, so is it possible that the crank is of by 180, making the intake and exhaust valves close at the wrong times, leading to the motor not stopping, i pulled the first spark plug, and noticed that at each full turn of the crank pulley, when i aligned with the marks it was top dead center, how ever every full turn the first is in TDC, but wouldn't each complete turn make the intake be up and on the next revolution making the intake down and so forth, could this be a possibility why it won't start as if its choking the motor or not opening and closing at the right time? ( correct me if I'm wrong just saying what i think and figured it works like this) need your guys input thanks a lot

[gedu]

If you match timing marks on flywheel and cam wheel, cams open and close in right order.

[euro_urs4]

If you match timing marks on flywheel and cam wheel, cams open and close in right order.

how do you get the flywheel to match up with the cam wheel? isn't the only way to install the flywheel one way with all the bolts put in a certain order? (might be a stupid questions) but then how would i be able to check if there aligned, if the cam wheel is TDC should the flywheel pin be visible in the hole where the sensors times the flywheel?

[willg54]

Flywheel can only go on 1 way...two holes aren't equi distant.

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[UrS4boy]

You are not giving us the full story, i.e. like has the head been off the car? There should be no way to have gotten the engine timing out as much as you are suggesting. If you are, your engine is b*ggered because it is an interference engine and the pistons will have hit and bent the intake valves like these ones:

[WabTheKing]

yes you can get it 180 out, if you do it pops back through the intake when cranking

[terrybullwon]

You are not giving us the full story, i.e. like has the head been off the car? There should be no way to have gotten the engine timing out as much as you are suggesting. If you are, your engine is b*ggered because it is an interference engine and the pistons will have hit and bent the intake valves like these ones:

Far from correct

yes you can get it 180 out, if you do it pops back through the intake when cranking

Yes exactly Wab, Sounds like its sneezing or if your unlucky it will back fire straight into the Inlet

You need to get a dial gauge and get No.1 to TDC and then dial the cams in are you using an adjustable pully?

[mcandmar]

As long as the crank pulley/flywheel marks are at TDC, and the cam pulley mark is at TDC with both sets of valves closed for cyl 1 i dont think you can get it wrong.

For sanity sake i always double check, as you turn the engine over cyl 1 moves down the bore (power stroke), then ~BDC the exhaust valves will open as the piston comes back up. The crank will now be at TDC marks again but the cams will be 180 degrees out. Continue to rotate the crank another 360 degrees (through the intake/compression stroke) and you should be back at TDC for both the cams and crank marks. Its good practice to turn an engine over by hand a few times, then double check timing marks and belt tension. If you have a 3B or 7A move onto installing the distributor and turn the engine over a few times, then double check, and check it all again for good measure :-)

[UrS4boy]

Cam and Crank Timing Marks

As long as the crank pulley/flywheel marks are at TDC, and the cam pulley mark is at TDC with both sets of valves closed for cyl 1 i dont think you can get it wrong.

Like these (they ALL need to be lined up at the same time)





Theory:


Reality (sort of):

photo courtesy of SJM Autotechik

[UrS4boy]

Far from correct

Maybe the problem is I don't understand where the "180 degree out" is located, i.e. the crank or the cam. Maybe I just can't understand how anybody could possibly put their engine together with having more than 1 tooth off on the timing belt.

This is what I understand: You could have the No. 1 piston back at TDC but at that point the cam would be off by 180 deg. This has to cause issues with valve to piston clearances:



There is one nasty possibility here: The crank pulley key has sheared or shattered and the timing is off as a result.

I don't know.

[terrybullwon]

The hint is back firing into the inlet. You should not see this on a standard engine though unless the cams are out

[UrS4boy]

The hint is back firing into the inlet. You should not see this on a standard engine though unless the cams are out

I am not saying it isn't possible to be 180 out. I am just thinking that if things were out that much, there will be valve damage due to the interference nature of the Audi 3B, AAN, ABY and ADU engines.

[terrybullwon]

I am not saying it isn't possible to be 180 out. I am just thinking that if things were out that much, there will be valve damage due to the interference nature of the Audi 3B, AAN, ABY and ADU engines.

Yes i dont think the exhaust cam could be exactly 180 out this would then cause it to crash into the exhaust ports

[UrS4boy]

Yes i dont think the exhaust cam could be exactly 180 out this would then cause it to crash into the exhaust ports

Semantics: The issue is not the exhaust cam or valves. It is the intake valves that are the interference part of this engine (Item 7 is the intake valve seat. Item 6 is the exhaust valve seat, well above the piston):

[terrybullwon]

Sorry my bad.... Either way i have seen my motor back fire into the inlet because the cams were to advanced