Timing Belt Problems

[nfpgasmask]

So let me get this straight, in my pictures below, is this the part that you all are saying I did backwards?





I've never quite understood what everyone is saying is wrong with my timing belt instructions. I suppose it should be gotten to the bottom of here and now. I am not trying to create an arguement or debate, I just want to understand what is wrong with my instructions, and also how my instructions worked fine despite there being something wrong.

Here are the things I can verify 100%:

1) When I was done with my timing belt install, everything worked fine. Not one single problem. VX fired right up.

2) When I removed my old belt, the LH and RH camshaft pulleys springed to the 12 o'clock position.

3) I never moved my crank once the old belt was off.

4) I followed this diagram EXACTLY when I lined up the new belt:


So where is the backwards part of my install?

Please help me understand so I can annotate my document.

Thanks - Bart

[SlowPro48]

Yes, that's it! The crank sprocket - it's #1 on the diagram you posted. #7 on the diagram points to the TDC notch in crank sprocket lined up with the TDC mark cast in the oil pump housing. #8 shows the dotted lines on the belt lining up with the mark punched in the rim of the sprocket.

If you check the Service Bulletin that Mark posted, you'll see a good picture at Step 26, which says, "Align the dotted-white line of the timing belt with the white timing mark of the crank sprocket (180 degrees from TDC timing notch)".

You did the opposite, however. You lined the dotted-white line up with the timing notch, not the white mark - so your cams were positioned like they were supposed to be, but #2 cylinder was at Bottom Dead Center instead of TDC i.e., 180 degrees off.

As far as why it still works.... I'm not smart enough to know the details of why it works but the bottom line answer is that if you install the belt according to Isuzu's instructions, and then you rotate the engine a bunch of times, all of the pulleys and marks eventually line up as pictured in your how-to. Everybody knows this because your VX runs. My right bicep knows it because curiosity got the best of me. I installed the belt according to Isuzu's instructions but when it came time to spin the engine by hand to make sure there were no crunchy noises I went well beyond the two turns of the full Otto cycle in order to see how many turns it took before everything would line up the way you did it. The answer is LOTS. I can't remember exactly - wish I'd written it down - but I do remember my arm felt like it was about to fall off - and I was using a 2 foot long ratchet and all of the spark plugs were out...

The relationship between cams and crank and a particular spot on the belt is set by the gear and pulley ratios and the number of teeth between the pulleys. It's nothing but math. There's a definite number of crank turns before a particular combination of marks comes around again. A high school kid with a B average in algebra could probably come up with a formula to calculate that interval - but I cant! Hey maybe one of our non-U.S. members can figure it out for us since the rest of the world kicks our azz when it comes to math skills.

Even if we knew how it happens that you can start out with #2 at BDC instead of with the piston at TDC where you would normally expect to see it when the cams are lined up for compression stroke, I'm not sure it would tell us whether it works this way by design or not. Wouldn't it be nice if we could lure an Isuzu engineer in here?!

[nfpgasmask]

OK, I see what you are saying, but this is why it is still very confusing to me.

Before I removed my old timing belt, I rotated the crankshaft pulley a few times, just so I could see everything line up and get a firm understanding of that.

Then I turned the crankshaft pulley and lined up both camshaft pulleys like so:



Once both camshaft pulleys lined up, the crankshaft pulley lined up like so:


At that point, I removed the old timing belt. With the old timing belt off, the half-circle notch on the BACK of the crankshaft sprocket is on the OPPOSITE side of the green painted tick mark on the FRONT of the crankshaft sprocket. The half-circle notch lined up with the white paint mark on the housing like so (note this pick shows the new belt installed):


I then installed my new timing belt from there to line up with all the marks, and it worked perfectly. So I still do not see how my instructions are off from the Isuzu instructions.

IMO, there is one or more of the following scenarios happening:

1) People, myself included, could be reading and interpreting the various instructions out there in different ways and thus, confusion is created.

2) The Isuzu instructions, videos and diagrams are explaining this is a way that confuses some folks.

3) My instructions are explaining this in a way that confuses some folks despite my absolute best effort to spell this out as simply as possible.

4) Some people who HAVE NOT ever done this maintenance are chiming in with opinions and information without actual experience to back their claims up.

5) People are not understanding where the marks are and where they should be lining up, or they are looking at my photos or the diagrams wrong.

6) People are not reading carefully enough and paying attention to the different things happening, ie, camshaft vs crankshaft, notch on back vs notch on front, dotted line on old belt vs dotted line on new belt, etc.

7) And lastly, the Isuzu instructions could be either wrong, or perhaps there is some variance between our VX's and the Trooper's 3.5. Meaning, maybe there are some slight differences between years or models that could be causing us to pull our hair out. Despite the fact that many of us on here could be considered VehiCROSS gurus, we don't know everything about what happened during the manufacturing process, video creation, and eveything else that happened while these vehicles were being manufactured. Errors are made, even by the big companies.

The only way that I could have done this the "right" way, would have been to remove my old belt, and then turn the crankshaft pulley 180 degrees to get the half-circle notch to line up at the opposite side, which imo, would have screwed up my timing and would have been completely wrong. The white dot and the half-circle notch line up. The green painted tick mark and the line mark on the housing line up. Both of those align opposite eachother.

I hope this makes sense, and again, I believe my instructions are right, and there is just some confusion in the interpretation.

Bart

Edit PS: Slowpro, I just reread what you wrote above.

If you check the Service Bulletin that Mark posted, you'll see a good picture at Step 26, which says, "Align the dotted-white line of the timing belt with the white timing mark of the crank sprocket (180 degrees from TDC timing notch)".

I absolutely DID NOT do the opposite of what you are saying, clearly presented in my photos above, so which one of my pictures is confusing people? Or am I still confused? The "white timing mark" the Bulletin is referring to, MUST be the white dot at 180 degrees from the TDC notch, correct????

[nfpgasmask]

OK, I just looked at the Service Bulletin again.

Step 26. This photo illustrates EXACTLY the same thing as my photos. Please compare them.







So again, not trying to argue, but I think my instructions are 100% correct, and followed the Isuzu instructions to the letter.

My goal was to provide timing belt instructions in a more clear way that Isuzu presented them, and if there is a mistake or even a tiny bit of confusion that I caused, I apologize. I just want to clear this up so no one has trouble in the future.

Bart

[nfpgasmask]

OK, had some more time here at work and so I downloaded the video and watched it again.

I think I see where the confusion is, and where my instructions could be considered backwards.

There are two marks on the crankshaft, one is the green "reference mark" on the outside of the crankshaft pulley, and the other is the half-circle notch referred to as the "timing mark" in the video. Its actually really hard to tell in the video because it is compressed and very hard to make out those fine details.

Anyway, I guess in my instructions the reference mark and the timing mark are backwards. I suppose this would not be the case had I turned the crankshaft one more full revolution.

Now, the reason why this worked obviously, is because both of those marks are just reference marks for the timing and the new belt installation. Apparently, so long as the camshaft marks are lined up, changing the belt whether at TDC or 180 degrees from TDC doesn't matter, so long as you install the new belt properly and you don't turn the crankshaft.

So, I can now say that I understand the discrepency, and I can update my instructions accordingly.

Now, to the OP, I hope that you did NOT turn your crankshaft pulley once you had the old belt off. If you did that, then you are 180 degrees off most likely. The other problem could be you are just a tooth off.

Anyway, I think my doing it backwards was simply a result of the video and diagram not clarifying between the two different marks well enough.

Bart

[SlowPro48]

Anyway, I guess in my instructions the reference mark and the timing mark are backwards. I suppose this would not be the case had I turned the crankshaft one more full revolution.

Wha? If you had turned the crank one more revolution you'd be right back where you started - i.e., still 180 degrees off. Turning the crank is not the problem. If you want to avoid confusion, the problem is telling people to align the dotted line on the belt WITH the TDC notch - when instructions from Isuzu say align the dotted line on the belt "180 DEGREES FROM TDC timing notch".

Note it's only a problem if you want to avoid confusion - it's not a problem from a practical/operational standpoint. As you well know, the VX runs just fine with the crank aligned 180 degrees off. All you're doing is making it fire the #5 cylinder when it thinks it's firing #2. Like I said in a previous post - just one of the advantages of a wasted spark ignition!

If you leave the instructions and pics as-is then, like the OP, people are going to continue to be confused during timing belt installs. And if they end up ignoring Isuzu's instructions and doing it as depicted in your how-to, it might even cause confusion well after the install. I can imagine the frustration of a future owner or his/her unfortunate mechanic when he discovers the high misfire count DTC he's been chasing on #4 is actually due to a bad plug wire on #1 and a confused PCM that thinks #1 is #4, #2 is #5, #3 is #6, etc!

Bart, I really appreciate the time and effort you put into your timing belt how-to. It helps all of us a great deal to have picture-rich start to finish instructions all in one place. If you truly want to eliminate future confusion though, modifying the instructions for that one step (installation of the belt on the crank pulley) to reflect what's in the manual and the TSB would take care of it - no further explainations/annotations/discussion needed ever again.

[SlowPro48]

OK term117, sorry for the TJ, let's see if we can get your prob figured out.

When you say it "didnt turn over at all" do you mean when you engaged the starter absolutely nothing happened i.e., the engine did not spin at all? Or do you mean it turned but didn't start?

Did you spin it by hand for a couple rotations to make sure there was no interference after you put the belt on?

And what do you mean when you say you "tried to start the car without putting it back together"?

[nfpgasmask]

Note it's only a problem if you want to avoid confusion - it's not a problem from a practical/operational standpoint. As you well know, the VX runs just fine with the crank aligned 180 degrees off. All you're doing is making it fire the #5 cylinder when it thinks it's firing #2. Like I said in a previous post - just one of the advantages of a wasted spark ignition!

So, are you saying that because of the way I did my timing belt swap, I must be misfiring now? Or are you saying because of the mistake in my write-up, people could get confused and then their VX would misfire after they do it wrong? If I was misfiring, wouldn't my VX run like crap, throw a CEL or whatever?

To me, my install worked fine because essentially I am just taking the old belt off, and installing a new one without disrupting anything. Technically, like you said, that would work regardless of where your pulleys are, as long as the new belt goes on in exactly the same way the old one was on.

Of course, I would love to fix my instructions, but I am not about to tear into my VX just to snap 2 or 3 pictures of this the right way. So, if there is someone out there who is doing this and would like to provide correct photos, I would gladly update my instructions, but for now, I have removed the write-up from my old website and I currently have no link to it up on my new website. As for the how-to section on this forum, the pdf probably should be taken down until the error is corrected.

Anyway, I appreciate you taking the time to spell this out, honestly, it wasn't until I studied the pictures, the videos and the diagram again and again before I realized where the mistake is.

Now I am just concerned that my VX could be screwed up somehow??!?!?

Bart