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Timing belt issue. Cam sprocket marks moved 4 teeth!


Nefarious
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Hey everyone. I have a freaking weird question.... I just did the timing belt on my gfs vg30e wd21. I have done timing a few times (even on a z32 vg30de) so it's not new to me or anything... I was extremely careful when I put everything back together. I marked the new timing belt exactly to the marks of the old timing belt I pulled off. I lined up the new belt to the cam sprockets and crank sprocket. The marks on the cam sprockets lined up perfectly to the backing plate of the timing cover and the crank sprocket lined up to the oil pump marking I made. Easy, right?. Went right on ,didn't have to adjust anything to make it fit.

 

Weird part is, i put it all back together...go to fire it up...no luck, it turns over and tries to fire a bit (very faintly) doesn't even catch and try to run, just a few putts. Just sounds like the starter is turning the motor and thats it. So I tear everything back down again, take off the upper and lower timing cover again and now my cam sprockets don't line up to the crank sprocket anymore!

 

With piston 1 at TDC the crank sprocket still lines up with the oil pump mark I made perfectly, but the cam sprockets have now moved themselves 4 teeth clockwise! (looking at the front of the truck). The distance between the 2 cam sprockets is still exactly the same, but the distance between the left side cam sprocket and the crank sprocket is now 4 teeth closer together.

 

I'm not going by the belt marks here, these are the marks on the actual sprockets.... I have never had this happen before... The only thing I can think of is the timing belt is the wrong size. it says 133 teeth right on it, but who knows.... The other thing I don't get is how would cam sprockets move in relation to the crank sprocket, but not move in relation to one another, they are still the right spacing between the two cam sprockets, but the spacing between the LH side cam sprocket and crank sprocket are now off.

 

I'm hoping no valves are bent as I have heard no noise out of the ordinary and the motor still feels normal to spin with the breaker bar... We are going to pick up a new belt tomorrow (this one was from ebay, but I have used this same brand on my z32 300zx without any issues at all) and make sure it has the timing marks on it already.

 

Please if anyone has any clue why the cam sprockets could get off timing in relation to the crank sprocket but not to each other. I'm really hoping it's just the new belt as it was fine before I took it off! but I still don't understand how the cam sprockets could move equally 4 teeth closer clockwise to the crank sprocket. any help would be good! thanks

Edited by Nefarious
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Sounds like you have your timing marks all correct. It must be the wrong belt. You might want to check the compression after the belt change for a "peace of mind" to make sure none of the valves kissed the pistons.

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Yeah I was thinking i should probably check the compression.... ill have to pick up a compression gauge next time im at princess auto. man I really hope that's not the case, I'm being optimistic as I really don't feel like tearing down the head to replace the valves. Worst comes to worst I could just vg33e swap it like I did to my truck... well here's hoping they are fine.

 

so it would be possible to have the locations of the cam sprockets vs the crank sprocket become changed by a wrong sized belt? It just seems strange to me how that would work if the number of teeth between 2 points wouldnt be able to change (i think) as long as there was adequate tension.

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Did you get a tooth count from the right bank cam to the crank shaft? I figured out my jumped timing dilemma by the tooth count between the right cam and crank. In my case, the soupy mud (from my sig pic) entered the timing belt chamber and hardened causing the belt to jump teeth from the crank shaft. What a headache that was to diagnose. icon_censored.gif

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so you jumped a few teeth on the crank and the valves were okay?

 

I used the marks that were on the old belt and transfered them over, I counted 40 valleys in between the RH and LH cam sprockets and 43 between the LH cam sprocket and the crank sprocket. that's what the fsm said is normal for a 94 pathy. this is a square tooth 93 but im assuming it's the same tooth count.

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Mine (VG33E) has the same square tooth count IIRC. Someone might chime in and correct the numbers for me.

 

Yeah, I can't believe my valves survived. From what I understand, the VG33 is an interference motor. I checked my compression ranging from 130-148 psi. There may have been some minor collision on the 1-3-6 bank. She purrs like a kitten these days.

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hmm, well I am hopeful her truck will be fine too!! She hasn't even been able to drive it yet, we got it really cheap (400$) and its absolutely MINT zero rust 93 se with every single option as far as i know. just been fixing up the issues it had and this was the last thing to go. I really want to get her driving it for winter, haha.

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Well the old timing belt I pulled off had alignment marks printed right on it, I just transferred them over to the new belt, I double checked the count 3 times between the lines...hmm well I'm going back at it today..its all torn down just need to loosen the tensioner and line everything back up. Man I wish parts store belts came with the lines on them!

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Did you turn the engine over at least twice after you put the timing belt on and tightened the tensioner? Where did you set the tensioner? It should be set with the allen key hole at either the 5 or 11 o' clock position. Preferably the 5 o' clock because of where that spring is. The belt can jump because you are going from 0 to 1500 rpm in less than a second and that's a crazy amount of force on the belt. If the belt was not seated and/or tensioned properly it will jump once you go and start the engine. Good luck with the re-install.

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Please don't post identical threads in different areas, it really confuses the input and anyone searching for information. One thread is plenty. Thanks,

 

B

(I've deleted the one in the 90-95 section that got no responses)

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oh hey. yeah sorry that was my bad, thought the connection got interrupted on the other one so i posted it here and didnt notice the other one worked. wont happen again, anyways i did go to napa, got a gates belt, lined everything up again, went to start it again and bam, fired right up! so far so good, no weird noises or anything, the belt must have skipped some teeth.... i thought i had tensioned it right but maybe i didnt, anyways it runs good now! ill still do a compression test to confirm no bent valves but it runs good, has good power, clean exhaust and no strange noises. i guess i got lucky! lol. the napa belt (made by gates, but cheaper) was only 23 bux and had the marks. thanks for the replies everyone!

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yeah ill be picking up a compression gauge this weekend when i can make it down to princess auto, until then it is finally time to finish working on my pathy!!! :D rear axle swap, some exhaust work, and finish putting the intake manifold back on and she is done :D

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