Timing Belt Problems

[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

[term117]

Bart in your guide your both your Cams spring to 12(as compared to the floor) pointing straight up as mine did when I first took the belt off. After rotating the engine a few more times(when I thought I had done it incorrectly) they did not spring to 12 and thus a relied on the TSB because I didn't want to mess things up. The TSB and your guide have the cams pointing in different directions so it may be that the way in your guide is the correct way to have the crank shaft when you do it that way.

If I had my car all apart as in not following any of the steps of putting it back together(no radiator and such) and just starting it after I put the belt on it should still start right? I was just going to let it run for 5 secs to make sure its on correctly.

As I said I put it together exactly as in the TSB and it turned for about 3 seconds and stalled. I dont know if I have to open the engine and adjust the cams from inside the engine or if that would even help at all.

Slowpro it sounds like you really know what your talking about. If I could get you on the phone that would be awesome.

[SlowPro48]

So, are you saying that because of the way I did my timing belt swap, I must be misfiring now?

No, dude, it's not screwed up! It's all good! And everybody that followed your how-to is all good too. I wasn't saying it would cause a misfire I was saying if there's a misfire it would be attributed to the wrong cylinder which might cause some confusion when it came time to diagnose the problem. But in no way was I saying installing the timing belt according to your instructions will cause misfire or poor running.

Background info: These engines are even fire V6s so there's a power stroke every 120 degrees. Firing order is 123456 with 1 & 4 paired, 2 & 5 paired and 3 & 6 paired and by that I mean rising and falling together so that while one is at TDC at end of compression stroke, its mate is at TDC at end of exhaust stroke. The ignition system is set up so that the pairs share spark. The one that's on the compression stroke goes bang when it gets spark. (and a few degrees later will be into the power stroke) Since the other one is on exhaust stroke the spark does nothing - it's wasted.

The PCM uses two sensors to determine which cylinder is firing - one to determine crank position (that narrows it down to two) and one to determine camshaft position (that tells it which one of the two is on power stroke and which one is on intake). When the PCM senses sudden drop in crank speed (i.e., a misfire) it assigns it to a particular cylinder, keeps a count of the misfires and if there are too many, throws a DTC implicating the bad cylinder.

The belt change TSB has you align the valves and crank for #2 at TDC on compression stroke which means it's mate # 5's valves are positioned for end of exhaust stroke.

Here's why I said the PCM could get the cylinders confused: I know from working on bikes with wasted spark ignitions that as long as you've got the crank right, you can set the valves up 180 degrees off and since there's a spark every time the piston is near TDC, the bike will fire and run perfectly because the with the next turn everything will line up properly for compression stroke. If the VX runs with crank 180 degrees off like in your pictures then the PCM would be sensing that #2 is firing when in reality #5 is firing and thus if there were misfire it would assign the "blame" to the wrong cylinder. I was thinking it actually would run like that because when you set up the valves like the TSB says with #2 at TDC on the compression stroke then #5 is at TDC on exhaust so the exhaust valve is open and intake is closed. Then if the crank is positioned as per your pics, with the next turn I think both valves would be closed in #5 and what used to be a wasted spark during the exhaust stroke is now happening in the compression stroke - so it fires up and runs fine - but the sensors are telling the PCM that #2 is firing when #5 is firing and vice versa.

I'm thinking more clearly now than at 2AM last night though and am now doubting it will run with the crank 180 degrees off. The problem is I mostly work on singles and when you throw in multiple cylinders and DOHC it warps my mind! Or what little is left of it. I totally suck at visualization in 3D. I'm gonna have to draw some pictures I guess!

To be continued...

[nfpgasmask]

OK, I see, I think I got it. Yeah, can be confusing for sure.

Bart

[SlowPro48]

OK, Bart I was dead wrong about it being able to run if the cams are lined up like the TSB says but the crank is positioned so that #2 and #5 are at BDC instead of TDC. I diagrammed it out and it looks like in the #2 cylinder from 180 to 360 the exhaust valve would be opening while the piston was going toward TDC, so no prob there - then from 360 down to 540 the exhaust would be closing and the intake opening, no prob there either, but then on the next upstroke from 540 to 0/720 the intake would be open. Big problem! There would be no compression just the sound of air huffing back through the intake. Meanwhile, over in #5, the intake valve would be opening while the piston was going up from 180 to 360 so it would be huffing back through the intake too - then from 360 down to 540 both valves would be closed so it would be sucking air past the closed valves. The other pairs would be doing the same wacky stuff.

In other words, there would be no combustion, just a bunch of huffing and puffing and sucking noises. And maybe an occasional backfire. It would sound a lot like a Zumba Gold class without the music and the hot little instructor girl named Krista. Ah, but I digress... Bottom line is there's absolutely no way it would run if it were 180 off. It will only run one way. So if yours is running like it's supposed to then it's set up 100% right.

Now that I see that one little inconsistency is totally harmless I think you oughta leave the how-to up. It's too good of a write-up to keep under wraps. It would still be nice to have the how-to and the Isuzu instructions match but I don't see any harm in keeping it available with a caveat that if you've lost timing because of a broken belt or inadvertently turned the cams then don't refer to the how-to, use the TSB instead. Maybe next time someone does a timing belt change they'll line it up the Isuzu way before removing the belt and take some pics for you. Hey if I'm still around and able, in another 80K miles I'll take pics not only of the crankshaft sprocket but also the cams. It will be time to check clearance so the valve covers will have to come off.

Sorry if I gave you a scare there - shoulda diagrammed it out before running my mouth I guess. Just can't trust this worm-eaten brain anymore!

[SlowPro48]

If I could get you on the phone that would be awesome.

Dude, I don't know how much help I'd be! But I be glad to talk to you and do what I can to help you figure out what the problem is. One thing you said in that last message made me wonder. You said "as compared to the floor" but When the TSB says rotate the cam sprocket until it springs to 9 o'cock or 12 o'clock they mean with respect to the block deck, not the shop floor. If you positioned them at 12 o'clock with respect to the floor they are 37.5 degrees off and that would be a problem.

Anyway if you want to call me just multiply 480583651 by the number of days in a week and that's my phone number.

[Scott Larson]

Bunch-O-Troublemakers...

[nfpgasmask]

Sorry if I gave you a scare there - shoulda diagrammed it out before running my mouth I guess. Just can't trust this worm-eaten brain anymore!

Naaa, you didn't really scare me, obviously my VX is running, and has been, without issue, so I guess I was more worried that it caused the computer issue you spoke of. But, for me, I have plans to be buried in my VX so the next owner of my VX will hopefully be earhtworms.

Anyway, this was a good discussion. These are important issues.

Bart

[SlowPro48]

Larson, what are you doing here? Didn't I fire you? Are you going Costanza on us?

Hey Term117 did you get it running yet?

[CrnCnn]

I dont want to start another thread for this question.

Does the bolt in the crankshaft pulley come out like normal? Meaning is it reverse thread?

I cannot get it out. I borrowed a impact gun from a friend and its not budging. I sprayed some PB blaster on it and will try again in the morning.

[Zu4two]

Crankshaft bolt is normal thread. It is on there at ~125 foot-pounds, so it doesn't come off easily.

[CrnCnn]

Thank you! I will just have to try harder.

[Chopper]

not that it matters ....but I followed the Bart layout pretty closely last year, and the VX runs like a champ
In 40 or 50,000 when I do it again, I'll try the Isuzu method