Engine question

[Buffy]

Well I've spent the morning tearing into my engine to see if I can see what is going on with it. I did a compression test and here is what I found:

90 100

120 100

110 100

front

I took the timing cover off the passenger side and everything seemed ok. I took the valve cover off and still everything looked good. Had the wife crank it while the cover was off too see if I gould see anything going on. Got a good oil bath but other than that nothing out of the ordinary. The sound seems like it is coming from under the cylinder head now. Just not sure what my next move should be. What should the compression be on the cylinders?
I am perplexed because the tapping will stop sometimes and then go back to tapping.

Any suggestions???

[Mile High VX]

Here are the inital results from another member that had a bad valve. He's in the UK so not sure if the measurements are comparable, but it's the only one I remember seeing recently.

1 = 190
2 = 170
3 = 180
4 = 0
5 = 170
6 = 165


Guess which cylinder had the bad valve...

The workshop manual list the desired compression at 14.0 Kg/cm2. So to convert that to psi you simply multiply by 14.223 and get 199 psi.

Looks like you may have a gauge issue, or you're gonna need some rings.

Hope this helps...

[Buffy]

I did the compression test on a cold engine and the manual says to have the engine at normal operating temps before testing. I guess I need to warm up the engine and try it again. I just can't figure out the knock.

[SilverBullet75]

http://www.vehicross.info/forums/sho...belt+tensioner

[Buffy]

I may go ahead and do that, heck I am into it this far. I did download the manual and follow the compression testing procedure. The numbers came back much better:
205 210

200 200

195 205
front

[Mile High VX]

I may go ahead and do that, heck I am into it this far. I did download the manual and follow the compression testing procedure. The numbers came back much better:
205 210

200 200

195 205
front

That's what I'm talkin' 'bout!

[Scott Larson]

So confused! I followed Bart's how-to after perusing all the other how-to's on the subject and had no issues/questions whatsoever...great tech write-up Bart!! Still curious about the "Chocolate Monkey" though...

[nfpgasmask]

Still curious about the "Chocolate Monkey" though...

That was inserted by Tom, you'll have to ask him...

Bart

[SlowPro48]

Yes, Scott, it IS a great write-up. In fact I think it's the best I've ever seen as far as attention to detail, how methodical it is and of course all the pics are very helpful - so Bart I hope you don't think I'm picking on your How-To. Burlington Buffy asked if he had his shyte lined up right and I just pointed out it's 180 degrees from what Isuzu says to do. I've already presented my hypothesis as to why it works when lined up with #2 and #5 at BDC instead of at TDC like the manual says they should be - but I'll leave it up to someone else to come up with a definitive answer - or for all I care it can remain a mystery like that thing hovering in the back yard when I was a kid or the strange, strange pond with sides like glass in the woods near here....

That is all.

[nfpgasmask]

SlowPro, not at all. For me, it's just that I want my how-to to be correct, accurate, concise and NOT confusing. Most of all, I don't want to point anyone in the wrong direction and have them eff up something with their VX.

The "chocolate monkey" thing might just do that (), so I always point people to the original how-to here:

http://www.nofuture.com/myvx/how-tos/tb/tbelt.htm

The above link is from my website, and if I make any revisions, you will see them there, but not in the PDF that Tom made of my original how-to back when I originally posted it. In fact I do think there are some minor changes on my site that ARE NOT in the PDF currently. Plus, I think my website is a better format and easier to follow. While the PDF is easier for people to find, I encourage everyone to visit the instructions on my site over the PDF.

I think the most confusing part for me now, is I sit here wondering what would have happened if I was to:

A) remove the tensioner
B) remove the original belt
C) turn the crankshaft pulley to move the notch to the right side, aligned with the mark on the oil pump housing, with the green line on the top of the pulley on the other side
D) put new belt on

Would my timing be OK or off? It's just so weird in my head because with the original belt still on, when I turned the crank shaft pulley to align the LH and RH camshaft marks, the notch was ALWAYS at the 9:00 o'clock position and the green line always lined up with mark on the oil pump, so I figured I had it right.

Personally, I think the Isuzu shop manual sucks. It's vague, the illustrations are terrible (they look like 10th generation photo-copies), and it assumes you have been a mechanic for 25 years (can't fault them there though).

Are there any other folks besides Mark who have done the timing belt change themselves? I'd be curious to know how things look for different people. SlowPro, you did the swap yourself and aligned the notch in the back of the crankshaft pulley with the mark on the oil pump. So, when you did it, did your marks on the LH and RH line up as well? So weird.

Bart

PS - I started working on a new how-to for the tranny fluid change but my camera's flash crapped out in the middle of doing it.

[Buffy]

I wondered the same thing. I would think that you would want to pull a valve cover and see if the cam timing marks are lined up. If they are I would think you could do that. I am just going off what was said in the "Lost Timing Reference" video on the web. My passenger cover is only sitting on the head so I may back the pulley to the reference mark on the cover, pull off the cover and see if I see the cam timing marks.

[psychos2]

I think the most confusing part for me now, is I sit here wondering what would have happened if I was to:

A) remove the tensioner
B) remove the original belt
C) turn the crankshaft pulley to move the notch to the right side, aligned with the mark on the oil pump housing, with the green line on the top of the pulley on the other side
D) put new belt on

Would my timing be OK or off? It's just so weird in my head because with the original belt still on, when I turned the crank shaft pulley to align the LH and RH camshaft marks, the notch was ALWAYS at the 9:00 o'clock position and the green line always lined up with mark on the oil pump, so I figured I had it right.

from what has happened to some on this site and from what I have read about getting the cams back in time if the belt breaks.
1st make sure the marks are lined up before removing the belt.
2nd don not turn the cams without the belt being on. if you were to turn the cam 1 turn and put the belt on the cam timing would be off.There is a TSB about retiming the cams take a look at it and it will answer the question as to what would happen. shawn

[tom4bren]

The "chocolate monkey" thing might just do that (), so I always point people to the original how-to here:

http://www.nofuture.com/myvx/how-tos/tb/tbelt.htm

The above link is from my website, and if I make any revisions, you will see them there, but not in the PDF that Tom made of my original how-to back when I originally posted it. In fact I do think there are some minor changes on my site that ARE NOT in the PDF currently. Plus, I think my website is a better format and easier to follow. While the PDF is easier for people to find, I encourage everyone to visit the instructions on my site over the PDF.

Yerrrr Welcome!!!

I tried to be true to Bart's write up when I converted it to PDF (only took a little comic liberties). In retrospect, I should've added a hyperlink to his website so that any updates could be tracked. The PDF isn't supposed to do anything more than provide a copy for peeps to archive if they wish & print a throw-away copy to have in the garage whilst doing the repair.

Back on topic: Take the pix of the timing mark alignments to an authorized Isuzu repair facility (yes, those still exist) & find out if it appears out of spec to them.

IMHO, although the mark is obviously off slightly, it's not off by the amount that a 1 tooth adjustment on the belt would correct. If you adjust the belt by 1 tooth, the mark may actually be on the other side of the reference. This makes me think that it's a tensioner issue.

BTW, Chocolate Monkey:

[SlowPro48]

SlowPro, not at all.

Well that's good. Looked like people were getting DE-fensive so I thought uh-oh I guess that means I came across as O-ffensive. I never mean to offend anybody here* but sometimes it happens without my even trying.

Yeah I lined everything up just like Isuzu says to do it - with #2 at TDC and both cam pulleys lined up withe their marks. Then I took the old belt off and put the new one on. I have no idea where the dots and lines were on the old belt before I took it off. I couldn't see them but to be honest I didn't look that hard because I knew they didn't matter. All these marks are just there for you to verify that you have the right number of teeth between each pulley when you put the new belt on.

I think what's confusing the situation (for me at least) is that the cams don't turn at the same speed as the cam pulley** so you can't relate crank position to cam position easily just by looking at the pulley. One thing is for certain: although Isuzu says line the cam pulleys up with #2 piston at TDC, there is also a point in the rotation sequence where the cam pulleys are on their respective marks and #2 piston is at BDC - otherwise your engine would not be running.

If you did what you suggested - took the belt off and spun the crank 180 degrees and reinstalled the belt, your engine would not run. If you did the opposite - i.e., kept the crank where it was but spun all the cams 180 degrees (the cams themselves, not the cam pulley since it's not a 1:1 ratio) I think it would run just fine because of the wasted spark ignition system. I don't know if #2 is on the compression stroke or #5 is on the compression stroke when lined up like Isuzu says but it doesn't matter because both coils are fired by the same trigger so if you took the belt off and spun the cams around so as to swap the suck squeeze bang blow cycle from one cylinder to the other, the engine wouldn't miss a lick since it would still be getting spark when it was time to bang. If you spun the crank like you suggested though it would try to blow when the valves thought it was time to suck, suck when the valves thought it was time to squeeze, and blow when the valves and thought it was time to bang. It would also squeeze when the valves thought it was time to bang of course - but they wouldn't care - they're lazy - even when your engine is running properly they think squeezing and banging are the same thing - they just lay there with their springs extended, doing nothing - letting the ignition system do all the work...

Buffy's the one who could put this discussion to rest. Not only has he got the timing belt covers off at this very moment but also the valve covers so he can actually see everthing that's going on. Come on Buffy - dish out some info here - how many teeth on the cam drive gear and how many on the cam? How many teeth on the crank pulley and how many on the cam pulley? Line that baby up like Isuzu said to do it - then crank away and see how many turns it takes to get to Bart's configuration and how many turns it takes to get back to the Isuzu configuration. I bet Bart's is exactly half way through the cycle. Oh, and BTW Buffy - eat your Wheaties first!


*except for SpudBoy of course. But he's apparently too busy enjoying his white bread and crackers in Idaho to post here anymore. If he ever shows up again though I'll do my best to offend him because he and his ilk actively try to kill my joy (and yours too if you like to take your VX off-road). Oh, wait... maybe he's decided to diversify his honky self and move to NC - I think I see him in the background in this video! http://www.youtube.com/watch?v=roFB7bGCAgc

**I'm guessing they turn at 2/3 speed since it's a 60 degree V engine but yet you turn the left (even) bank pulley 90 degrees after it "springs" to reset the cams when you've lost timing due to belt breakage, etc. But then again if you check the illustrations in the shop manual it looks more like 3/4 speed based on the sizes of the gears so who knows. Either way the cams are under driven and that make it hard to visualize what's going on.

[Scott Larson]

[QUOTE for all I care it can remain a mystery like that thing hovering in the back yard when I was a kid or the strange, strange pond with sides like glass in the woods near here....

OMG, you saw that too!!!