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redporsche
Joined: 07 Feb 2013
Posts: 14
Location: Houston, TX USA
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 Posted: Tue Mar 26, 2013 1:18 am Post subject: Timing belt replacement |
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Well I listened to a friend of mine who races 924 and he suggested I replace my Timing belt since it's been there for who knows. I got out my Haynes book and followed the sparse directions. After removing all the belts and covers trying to get the timing belt off was a challenge to say the least. The reinstalling the new one was even more fun. I had to remove the skid plate to see the bottom of the crank gear. Anyway got it back on. Now here is the problem with the timing belt on and tightened to the almost 90degree tighteness the motor tried to start but sounds like it is locking up. Crank a little lockup, crank more lockup. Anyone have any suggestions. I didn't turn the crank or the cam gears after the removal of the original belt. I need help.
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Tue Mar 26, 2013 1:43 am Post subject: |
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I would verify ignition timing. Putting on a belt that was not stretched to shite might have advanced it to the point where it is behaving as you describe.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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emoore924
Joined: 13 Apr 2004
Posts: 2822
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| Posted: Tue Mar 26, 2013 2:28 am Post subject: |
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To expand a little on that, you need to be sure that three parts of the engine are working together -- crank (pistons), cam, and ignition timing (distributor).
Do a search here and you should find several threads on how to do this properly.
Hopefully you're not working with a turbo engine here... |
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Grenadiers
Joined: 20 Feb 2007
Posts: 3222
Location: Nelson, WI & Prescott, AZ
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| Posted: Tue Mar 26, 2013 4:24 am Post subject: |
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That lockup might be fuel related, may want to check your oil level. Also, when putting the belt back on, you have to spin the crank pulley CCW a degree or two. So when you tighten the belt with the tensioner, the crank pulley will move to TDC. A couple degrees off though shouldn't prevent it from starting. Recheck your cam and crank positions, and hopefully you set everything at TDC when you took the belt off.
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redporsche
Joined: 07 Feb 2013
Posts: 14
Location: Houston, TX USA
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| Posted: Tue Mar 26, 2013 4:38 am Post subject: |
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Thanks all good suggestions. I will check and keep trying.
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Wed Mar 27, 2013 5:11 am Post subject: |
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To expand a little further:
| ideola wrote: | You will need a 13mm wrench (for loosening the ignition distributor hold-down clamp), a flat head screw driver (helps with popping off the distributor cap spring-clamps), and a 24mm socket with a 1/2" ratchet and short extension (for rotating the crank).
Using the 24mm socket/ratchet, rotate the crank around to TDC. This is easiest to check by watching for the dimple on the back side of the cam sprocket, and bringing that dimple into alignment with the pointer on the end of the cam cover. (Side note: make sure the cam sprocket is on correctly...it has dimples on both sides, and it is a common mistake during timing belt service to put the cam sprocket on backwards. The sprocket has a shallow side and a deep side. The deep side with the VW/Audi symbol and other writing should face the windshield, the shallow side should face the front of the car. If you find the sprocket is on backwards, fix that NOW before going any further. Once you've verified proper installation of the cam sprocket, use the dimple on the deep side to align with the cam cover pointer. This is TDC).
Pop the distributor cap off and set it aside (no need to disconnect wires unless you think they may be on incorrectly).
Remove the 13mm nut on the distributor hold-down clamp, remove the clamp, and remove the distributor.
Carefully inspect the lip of the distributor. Just to the right of the electrical connection you should see a tiny scribe mark on the lip of the distributor. This is the TDC mark. When you insert the distributor, you want the rotor to point directly to this scribe mark. This is a little tricky because the helical drive gear will cause the rotor to rotate slightly as you re-insert the distributor. Before inserting, rotate the rotor slightly clockwise away from the scribe mark (about 1/8th to 1/6th of a turn). When you insert the distributor, the rotor should rotate back to the TDC scribe mark.
If your distributor has the vac advance/retard housing on it (most of them do), there are only a couple of positions that will allow the distributor to be freely rotated for final timing correction without interfering with the cam cover. What I usually do is have the vac housing oriented as depicted in the following photo:
Just make sure that when you insert the distributor that the rotor ends up pointing to the scribe mark. Once you have it back in place, you can fine tune the distributor rotation until it points EXACTLY at the scribe mark. Then torque down the clamp with the 13mm nut.
Reinstall the distributor cap. The ignition terminal on the cap that is directly above or inline with the rotor (now that it and the engine are all oriented to TDC) is the #1 lead. The firing order should be 1-3-4-2 in a CLOCKWISE rotation. So check the leads to make sure that they are connected in this fashion to the distributor and the correct spark plug. Correct as necessary. Again: CLOCKWISE rotation!!! If you put the leads on for counter-clockwise rotation, the car will fire, but it will only run on cylinders 1 and 4 because 2 and 3 will be exactly 180 degrees out of phase! The car will run this way (ask me how I know) but VERY poorly!!!
The car should now start with relative ease. Now you can break out your timing light and dial in the precise ignition timing you want. |
So, how'd you like to trade that underbelly pan for the beautifully written and illustrated advice above? 
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pmcaya2
Joined: 24 Nov 2005
Posts: 191
Location: Scio, NY USA
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| Posted: Sat Mar 30, 2013 2:11 pm Post subject: |
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| Also have a look at my post on timing belt alignment in the "how to" section - I think that its a straight-forward description of the procedure. - Peter |
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924 FAQ (Technical)
