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 Post subject: Timing chain issue.
PostPosted: Fri Jul 22, 2011 12:53 pm 
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Location: Nashville, TN
Okay it really looks like when the cam bolt snapped that my cam shaft and crank got out of alignment by one tooth or something. The truck runs at idle but will not rev or take load. Trying to avoid having to pull my engine and take it all apart. Does anyone have the original service manual and could tell me what position the cam and sprocket should be in when the the #1 cylinder is at top dead center? A buddy who works on older Chevy's said that we should be able to fix it if we know that when the number 1 is top dead center that the cam needs to be in the correct position.

Hopefully all that makes sense and you guys know what he means.

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1987 Pup 2wd regular cab short box with a 1.9 gas engine and stick shift. Pretty much a stripper with out a single option as far as I know but picked her up from a little old man who took real good care of her.


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 Post subject: Re: Timing chain issue.
PostPosted: Fri Jul 22, 2011 5:45 pm 
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Location: Wilmington Island, Georgia
in between listening to the president sound like a fool live on the 6pm news....
I'll try to relay what I have relearned over the past 2 days...if I can stop screaming.




I would put a timing light on and see if there is enough adjustment in the distributor to get it right. Working form there will tell you if you need to advance or retard in moving the belt.


remove the air intake pipe across the top of the radiator so you can see the timing mark....bump the ignition till you get TDC on the mark, then IF you think the belt has jumped....mark a spot on the belt and cog...pull off and advance or retard...

I'm a 2 stroke guy that has been working on my engine and am stuck at a timing mystery and have had no feed back here....thought I'd try to help some how. good luck

cw

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89 LS Pick up, 2.6l
Mods? Aluminum wire radio antenna.


"One of the most noble things you can do is kill the enemy"-Maj. Douglas A. Zembiec USMC. died May 11, 2007 in Baghdad, Iraq


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 Post subject: Re: Timing chain issue.
PostPosted: Tue Jul 26, 2011 12:26 pm 
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Location: Sunnyvale, CA
If the problem is that the timing chain (or belt) has jumped, this cannot be overcome by readjusting the timing.

The timing chain is a mechanical link between the crankshaft and the camshaft. It ensures that the valves open and close when the pistons are in the correct position.

The engine timing, set by rotating the distributor, is only to synchronize the ignition (electrical) with the pistons.

So, the timing chain and engine timing have two separate functions and one cannot be compensated for by tweaking the other.

The crank and the cam and the chain all have timing marks on them and when installed properly these things all line up with marks on the block and head so that you know it is right. The service manual should spell all of this out.

John

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1984 GMC S-15 Short Bed Pickup 2wd with Stock Isuzu 1.9L Gas Engine
4 speed manual, manual steering, manual brakes, original owner


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 Post subject: Re: Timing chain issue.
PostPosted: Thu Jul 28, 2011 9:19 am 
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Location: Clarksville TN
@sun I am having problems with my timing belt as well, this is the first time in approx 40 timing belts that I have messed up. I am going to work on mine again tonight and when I figure out what I messed up, I might be able to help you, if nothing else just some ideas I tried to get my timing right.

Btw have you got your cyclinder pressure up to normal ?

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1987 Isuzu pup 2wd Gas 117K, 31 mpg, new headgasket at 25 years old


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 Post subject: Re: Timing chain issue.
PostPosted: Thu Jul 28, 2011 9:22 am 
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Location: Clarksville TN
@redman Do you need isuzu manual or will a chilton's work?

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1987 Isuzu pup 2wd Gas 117K, 31 mpg, new headgasket at 25 years old


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 Post subject: Re: Timing chain issue.
PostPosted: Tue Aug 23, 2011 4:05 pm 
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Okay broken finger put this on hold and I am now back at it. I can't seem to find any way to line up the mark on the cam, housing and those on the sprocket... Any advice?

These pics were taken with the front aka #1 cylinder at TDC.

Image
Image
Image
Image

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1987 Pup 2wd regular cab short box with a 1.9 gas engine and stick shift. Pretty much a stripper with out a single option as far as I know but picked her up from a little old man who took real good care of her.


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 Post subject: Re: Timing chain issue.
PostPosted: Tue Aug 23, 2011 7:05 pm 
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Location: N W Arkansas
The mark on the cam and the mark on the rocker arm shaft bracket should align straight up, the dowel from the cam into the cam gear should also be straight up & aligned with the two marks and the mark at the crank should be at TDC. All these conditions together will put #4 @ TDC, which is what you want when doing cam work on a gas Isuzu 4cylinder. Both #4 rocker arms should wriggle, at least one #1 rocker arm won't.
The marks on the cam gear and the chain link are used to get the proper number of chain teeth between the gears for the tensioner to work right. They will never align with the cam marks. There is a similar indicator link that aligns with a slot in the bottom of the crank with #4 @ TDC. With the #4 piston up, the cam & gear installed with the marks up and both indicator links aligned with the crank and cam gear setting marks the timing chain is installed correctly. Your cam gear mark aligns, so only the crank gear could be off, pull the front timing cover to confirm if you're convinced the chain has jumped. Since you can loosen the tensioner, remove the cam gear and chain and drop them down through the head into the timing cover and the chain will remain in place on the crank there can't be a lot of clearance for the chain to pop off the crank gear then back on, but I guess anything is possible.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch.


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 Post subject: Re: Timing chain issue.
PostPosted: Tue Aug 23, 2011 7:21 pm 
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oldestisuzuist wrote:
The mark on the cam and the mark on the rocker arm shaft bracket should align straight up, the dowel from the cam into the cam gear should also be straight up & aligned with the two marks and the mark at the crank should be at TDC. All these conditions together will put #4 @ TDC, which is what you want when doing cam work on a gas Isuzu 4cylinder. Both #4 rocker arms should wriggle, at least one #1 rocker arm won't.
The marks on the cam gear and the chain link are used to get the proper number of chain teeth between the gears for the tensioner to work right. They will never align with the cam marks. There is a similar indicator link that aligns with a slot in the bottom of the crank with #4 @ TDC. With the #4 piston up, the cam & gear installed with the marks up and both indicator links aligned with the crank and cam gear setting marks the timing chain is installed correctly. Your cam gear mark aligns, so only the crank gear could be off, pull the front timing cover to confirm if you're convinced the chain has jumped. Since you can loosen the tensioner, remove the cam gear and chain and drop them down through the head into the timing cover and the chain will remain in place on the crank there can't be a lot of clearance for the chain to pop off the crank gear then back on, but I guess anything is possible.


Okay I am confused is it #1 cylinder or number 4 that needs to be TDC? I was told #1 a couple times before... And by number one that means the closet to the rad... If that is incorrect this could explain all my trouble...

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1987 Pup 2wd regular cab short box with a 1.9 gas engine and stick shift. Pretty much a stripper with out a single option as far as I know but picked her up from a little old man who took real good care of her.


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 Post subject: Re: Timing chain issue.
PostPosted: Tue Aug 23, 2011 8:11 pm 
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Location: N W Arkansas
#4 where you have the cam positioned in the pictures.
The cam position determines which piston is at TDC. When the crank mark reads TDC both #1 & #4 pistons are up all the way. With the cam marks pointing straight up both #4 valves are closed and #4 is at TDC on the compression stroke- and the distrubutor is pointing to the #4 firing position. Rotate the crank 360 degrees- it again aligns with the TDC mark- and the cam rotates 180 degrees, the cam marks are pointing straight down, both #1 valves are closed, distributor points to #1- and #1 is at TDC on the compression stroke.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch.


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