Im helping my friend with the rebuild of his 3vz.

Last night we thought we had the timing belt on in 5 min. Everything lined up, the marks on the belt with the cams, and the mark on the belt with the crank.

But when we turn the engine over by hand, the belt skips over a tooth, and it will keep doing that each time the engine completes a revolution. All new parts, tensioner, idler pully, water pump and belt.

Ive read posts about the timing job in general but nothing about the belt skipping. We cant see or hear the belt skip when we turn it over but when the marks come back up the cams, they are off a tooth towards the right (passenger side ha)

 

Don't worry about the marks on the timing belt. Worry about the marks on the cam, and crank only. The number of teeth on the belt is not divisible by the number of teeth on the cam/crank gears, so your mark on the belt itself will continue to move over and over. For example, the crank gear has 1/2 as many teeth as the cam gear, since they turn 2:1. The timing belt has to have a lot more teeth because it takes a long path around the cams and crank.

As long as the cams and crank are still on their match marks, the engine is in time.

 

As DC said, DON'T pay attention to the markings on the belt after the initial set-up. They will move. As long as #1 is at compression, and the cams are lined up your set.

If that's not the case, what brand belt did you use? OEM is the best there is. Genuine.

 

Thanks guys!!!! As for the belt, I have no idea what my friend got.

 

MAKE SURE you aren't one tooth off between the two cam pulleys (slight slack between the upper idler pulley & cam gears).

 

So how do you keep the cams from ending up one tooth off after two rotations?

I am having a similar issue. I line everything up, install the belt, two rotations later the cam sprockets are one tooth off from the crankshaft.

 

I used a wrench and moved the cam back slightly to get in to the next tooth (looking at it from front, turn slightly to the right) and once its in, turn back to the left to tighten the belt. (use a wrench to hold the crank pulley if you need to). Do the driver side, then pull the belt tight under the idler and onto the pass side. Hold the drivers cam with one wrench and do the same procedure with the pass cam. It will help take up any small amount of slack that can get you one tooth off. Make sure the marks all line up. Then set the tension and turn a couple times to make sure it worked.

 

They really should not put those marks on the belt, it just confuses everyone the first time.

As pointed about above, if the first time I put it on it ends up one tooth off, I move the cam sprockets back about a tooth and try it again. That has worked for me every time on both the 3.0's and 3.4's I have done belts on.

 

Do a search; there are SEVERAL great threads on this topic alone. For example:

https://www.yotatech.com/forums/f116...estion-187420/
https://www.yotatech.com/forums/f116...estion-118098/

..to name a couple.

 

[quote=OutlawMike;51238041]They really should not put those marks on the belt, it just confuses everyone the first time.
quote]

The belt I just did last week was from Toyota and it didn't have those marks on it. Worked fine and one less thing to worry about lining up.

 

If it's just the marks on the belt that are moving, you're fine. Recheck your marks on the cams vs the backing plate, and the crank dimple with the slot in the front cover. I will often slide the bottom backing plate back into place, and then the front crank pulley, and use the marks on those to verify nothing moved.

I once had someone deliver a Camry 3.0 belt, which is 1 tooth shorter or longer (can't remember). It'd start briefly, and die. 5 times I put that fugger on before I realized it was mislabeled.