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TDC mark slightly off
by
Settings
on 29 Nov, 2008 23:13
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1993 AAZ
Due to recent cold-start issues, I checked my IP timing this morning (it was bang on .039).
Easy enough to find TDC mark and lock the cam and IP pulley. However, once I looked back at the TDC mark I noticed that it wasn't perfectly centered in the inspection port as I've seen in pictures. It was closer to the side of the inspection port (ie. a few degrees off center).
In your experience, would that indicate that the timing is off a tooth or two? If I had to guess, that's about how far off center of the the inspection port it was.
What would the symptoms of being off a tooth or two be?
I was happy to find the IP set at .039, but that doesn't mean much if the valve timing isn't correct.
Jeremy
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#1
by
handedyourhat
on 29 Nov, 2008 23:51
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WOOOOW, GOOD FIND , I always wondered about that, I would like to know if all VW's pointers on the tranny bellhousing's are in the exact same spot on every MK2 tranny ? I am going to make sure to install a dial indicator on top of my piston to actually see that my build is really at TDC before I install the head !!!!! I am actually going to use a different 5spd so this will be a good example if it does line up exactly at TDC... I guess you are going to have to install a dial indicator down through one of the injector holes and through the precup to get to the top of the piston to measure exact TDC ?
Dan
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#2
by
Vincent Waldon
on 30 Nov, 2008 01:22
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Because the cam sprocket has no keyway and the pump can rotate on its mount the timing is pretty much infinitely adjustable.
Flywheel TDC is *the* reference (assuming the proper flywheel is used and installed correctly :wink: )... to me what you're describing is simply an engine that needs to be retimed, from the beginning: flywheel at exactly TDC, cam sprocket free to rotate, camshaft locked and shimmed as required, belt at the correct tension, pump with locking pin installed.
Having said that, if you found the pump timing (using TDC on the flywheel as your reference) to be correct then my guess is that your cold-start problems probably lie elsewhere... in my experience diesels are not particularly sensitive to small errors in valve timing. How's your glow plug system working ? Got good compression ?
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#3
by
Settings
on 30 Nov, 2008 09:18
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to me what you're describing is simply an engine that needs to be retimed, from the beginning: flywheel at exactly TDC, cam sprocket free to rotate, camshaft locked and shimmed as required, belt at the correct tension, pump with locking pin installed.
Having said that, if you found the pump timing (using TDC on the flywheel as your reference) to be correct then my guess is that your cold-start problems probably lie elsewhere... in my experience diesels are not particularly sensitive to small errors in valve timing. How's your glow plug system working ? Got good compression ?
Thanks Vince.
That's just what I wanted to hear. I figured when I change the timing belt (on it's way) I would retime the whole thing, I just wanted to know how urgent it was, and how much it might be effecting performance.
As for the cold start (below 5 degrees it cranks for 15 seconds with white smoke before it catches. Fine if block heater plugged in. Otherwise seems to run smoothly) I was starting with timing as a relatively easy adjustment could fix it. Changed all four glow plugs in September when I noticed the effects of the cooling weather. Voltage and restance withing range seen on this forum. I don't have a compression tester so I'll take it tot he shop for that this week. I've noticed a fine stream of bubbles in the fuel line between the filter and pump. Replaced the filter with no change. Hoping to borrow a mityvac this week to see if I can't narrow that down a bit.
Does the fact that a block heater helps narrow down the problem (ie. compression rather than air in fuel)?
Jeremy
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#4
by
the caveman
on 30 Nov, 2008 10:34
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When i took the head off my 1.9 d to repalce the HG before throwing that motor into my transporter, i checked the #1 piston height against the front pulley, [ it wasn't attached to a transmission yet so i couldn't check at that end] the TDC mark and the TDc of the piston were not in sync. I marked the pulley where TDC actually was and then put the motor together and into the truck. I noted as far as i could where TDc really was and where the front pulley was , and then when i checked at the trans marker ,it was out also. I ended up setting everything somewhere between real TDC ,the front pulley mark and the trans marker. Could be why even though the IP is at exactly 1mm , i have a fair amount of ignition marbling.
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#5
by
veedubcanuck
on 30 Nov, 2008 10:57
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One more thing, if this engine has never been touched and the timing is going off then you might want to check the crank sprocket...if it's been loosening off then it is possible that the key is wearing causing you to shift the timing. This might just be an early warning...
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#6
by
AudiVWguy
on 30 Nov, 2008 12:00
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Rig your dial indicator down through the #1 injector to the top of the piston. Easy to do, very accurate. should match with the arrow on the inspection hole. If not, make a new mark. I used a lightened flywheel (8lb) from a 16V and found the timing marks were different.
-JB
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#7
by
Settings
on 30 Nov, 2008 15:51
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Thanks everyone.
The engine is all OEM and hasn't had major work done on it. My concern was that if the flywheel was set correctly at the factory, then it could have been mis-timed during a previous timing belt change.
I'm hoping to replace the timing belt next weekend. I'll time it directly to the piston through the injector hole. I'll let everyone know what I find.
What exactly would I be looking for with respect the the crank pulley key wearing? Will it be obvious?
Jer
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#8
by
veedubcanuck
on 01 Dec, 2008 09:53
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Check to see if there is any wobble in the crank pulley when the engine is running. If it is nice and straight then it SHOULD be ok. The only real way to check it is to pull off the pulleys and timing belt gear and look for wear on the key and surfaces.
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#9
by
arb
on 01 Dec, 2008 10:04
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I'm hoping to replace the timing belt next weekend. I'll time it directly to the piston through the injector hole. I'll let everyone know what I find.
Good plan. I checked my TDC mark when I had my head off because I suspected there was a problem. There was not. It was dead on.
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#10
by
vwt4
on 01 Dec, 2008 10:06
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Check to see if there is any wobble in the crank pulley when the engine is running. If it is nice and straight then it SHOULD be ok. The only real way to check it is to pull off the pulleys and timing belt gear and look for wear on the key and surfaces.
Remove the pulley asap is my advice.
If you search my recent threads you will find why!
and vincent is spot on.
You can retime the engine and loosen the camshaft sprocket to allow it to move on the sprocket when you line all of the marks up and put tension on the belt.
Ive found a helper is useful to lock the flywheel through the inspection hatch to keep it right on TDC