Changed timing belt, now won't start

Post by **thecheat** » 02 Dec 2010, 19:21

We had to redo the timing belt four times and it took an extra three hours to get it right. The crank marks are near invisible and the cam marks don't exactly line up either. It sounds like you had it one tooth off but I'm surprised that it wouldn't start at all... Glad it's fixed though!

This is the first dual cam engine I've done a belt on... So much easier with sohc!

Post by **precopster** » 03 Dec 2010, 05:40

After reviewing this thread I just want to be sure so I've posted my own pic. Are you sure the marks on your crank look exactly like this pic? Can't even begin to understand how the engine can fire up unless they are at least close.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 03 Dec 2010, 06:09

This is happening often, folks set cylinder #1 at TDC because they cannot find the timing mark on the crank shaft sprocket...When that timing mark is lined up with the pip on the oil pump, cylinder #1 is NOT at top dead center...Note that the timing mark on the oil pump is not centered over the middle of the crank shaft, it is a few degrees off to the left...

See the very well documented and photographed write up on MVS about replacing the cylinder head and it will be obvious that piston #1 is not at TDC...I surmise that the reason for this is so that the intake cam can be rotated to the mark by hand (before the belt is installed) with out any of the intake valves striking the piston, which they will do if any piston is at TDC...The clearances are so close and critical that the pistons have half moon shaped grooves milled into them to allow clearance for the valves...

Post by **precopster** » 03 Dec 2010, 06:26

I agree with jerrymcc on this one. TDC is one or two notches away, going clockwise (I have a B5252S engine with the head removed on a stand and just checked it)

You cannot guess and must use a bright light to find the mark. The first time I searched for this mark, it took me fifteen minutes to find it. Now that I know what to look for....easy.

Timberwolf530 · Post by **Timberwolf530** » 03 Dec 2010, 06:32

precopster wrote:

After reviewing this thread I just want to be sure so I've posted my own pic. Are you sure the marks on your crank look exactly like this pic? Can't even begin to understand how the engine can fire up unless they are at least close.

Mine looks nothing like yours. No mark on H.B., and the sprocket mark is an extremely small v groove on the inside(toward the block) of the sprocket that is barely visable. I have 20/20 vision and it took me forever to finally find it. It's all put back together, or I'd take pictures. There are two marks on the block. I guess one is the oil pump mark & the other is the timing mark. Anyway, at TDC the almost imperceptable groove lines up closer to the small (front) mark, but still not exactly on it. It's not that tough to find TDC, so I think I will just use that method from now on. Then I'm sure it's lined up properly.

Post by **erikv11** » 03 Dec 2010, 08:32

precopster wrote:I agree with jerrymcc on this one. TDC is one or two notches away, going clockwise (I have a B5252S engine with the head removed on a stand and just checked it)

You cannot guess and must use a bright light to find the mark. The first time I searched for this mark, it took me fifteen minutes to find it. Now that I know what to look for....easy.

I noticed exactly this while I had the head off last week for a valve job: when the crank notch is lined up with the mark, #1 is still a couple notches counterclock from the piston being at its highest point. So I put it all back together that way, just as that is how it was when I took it apart.

But I don't get it. Doesn't that mean that when the cams are in the proper place (marks lined up with TB cover), the engine is a couple teeth away from TDC? Are you guys saying the timing is off a little bit, or that it is the way it should be? Is TDC when the notch is lined up on the crank pulley, or when the cylinder is all the way to the top?

zanzabar · Post by **zanzabar** » 03 Dec 2010, 10:51

Timberwolf530 wrote: Mine looks nothing like yours. No mark on H.B., and the sprocket mark is an extremely small v groove on the inside(toward the block) of the sprocket that is barely visable. I have 20/20 vision and it took me forever to finally find it. It's all put back together, or I'd take pictures. There are two marks on the block. I guess one is the oil pump mark & the other is the timing mark. Anyway, at TDC the almost imperceptable groove lines up closer to the small (front) mark, but still not exactly on it. It's not that tough to find TDC, so I think I will just use that method from now on. Then I'm sure it's lined up properly.

+1 I never saw any marks on the crank or harmonic balancer that looked anything like the ones precopter posted. I searched for 15-20 min as well. It's possible I still just missed them I suppose.

I'm interseted to hear about whether Timberwolf's method has resulted in the proper alignment or not. Do we have an expert that can verify this for us? This seems like it should be easy knowledge to obtain, being such a basic and important setting for proper engine performance.

Timberwolf530 · Post by **Timberwolf530** » 03 Dec 2010, 12:29

zanzabar wrote:
Timberwolf530 wrote: Mine looks nothing like yours. No mark on H.B., and the sprocket mark is an extremely small v groove on the inside(toward the block) of the sprocket that is barely visable. I have 20/20 vision and it took me forever to finally find it. It's all put back together, or I'd take pictures. There are two marks on the block. I guess one is the oil pump mark & the other is the timing mark. Anyway, at TDC the almost imperceptable groove lines up closer to the small (front) mark, but still not exactly on it. It's not that tough to find TDC, so I think I will just use that method from now on. Then I'm sure it's lined up properly.
+1 I never saw any marks on the crank or harmonic balancer that looked anything like the ones precopter posted. I searched for 15-20 min as well. It's possible I still just missed them I suppose.

I'm interseted to hear about whether Timberwolf's method has resulted in the proper alignment or not. Do we have an expert that can verify this for us? This seems like it should be easy knowledge to obtain, being such a basic and important setting for proper engine performance.

Yes, it is timed perfectly now. Runs as good as it ever did. The mark & the groove are supposed to make finding TDC easier than the method I used. In other words, when the v notch lines up with the mark on the block, C#1 is supposed to be at TDC. Unfortunately for me, when the marks are lined up, mine is not at TDC, so it actually made it a huge pain in the butt. The fact that the notch is practically microscopic doesn't make it any easier either.

zanzabar · Post by **zanzabar** » 03 Dec 2010, 15:52

The mark & the groove are supposed to make finding TDC easier than the method I used. In other words, when the v notch lines up with the mark on the block, C#1 is supposed to be at TDC.

Well, jerrymcc and precopster disagree with you here. Or am I missing something?

Retired MVS Contributor · Post by **Retired MVS Contributor** » 03 Dec 2010, 17:01

One should NOT be worrying about where TDC is, only where the timing marks are that the Volvo engineers designated...If one uses the timing marks on all three gears, it willl NOT be at TDC and it was designed that way so that the cams can be hand rotated to their marks without hitting the piston...If piston # 1 is at TDC BEFORE the belt is installed, cylinder #1 intake valves will strike the piston if the cam is hand rotated a little bit in each direction...Believe what erikv11 is saying, he saw first hand what I am saying when his engine's head was off...

Changed timing belt, now won't start

Re: Changed timing belt, now won't start