Will not start after some major work..... - JeepForum.com
 
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post #1 of 14 Old 06-07-2021, 03:57 PM Thread Starter
kb9mfd
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Will not start after some major work.....

Now I did it. Will not start, no compression.

Ok, for the long version. I was having low compression on cylinder 1. So I decided to change out the head because I believed it was a valve issue. I had a donor head resurfaced. When I took it all apart it appeared the head /valves were not the issue. So I proceeded to also, since is was apart, to replace the lifters, cam and timing chain. (it did have a lifter tick, unknown if it was related to the low compression.) The real major issue I had was timing. Before I took off the timing cover I set TDC compression on 1. The rotor on the spark plug pointed to the 1 plug and the piston was TDC, and the timing mark on the harmonic balancer was on 0. BUT, when I took off the timing cover the timing marks where not as described in the manual. Instead of the marks facing each other, the cam sprocket was 180 degrees turned. I was very puzzled. So I assembled it as the book said, having the timing marks face each other. To determine if it was right, I spun the engine and stuck two rods in the lifters for cylinder 1 and followed the lifters and stopped when it was TDC for compression, and sure enough the timing mark for the cam was 180 degrees. So I assumed that must be right as that was the same when I took it apart. I assume for timing they are referring that cylinder 1 is the front, as if I set the timing marks according to the book, that is TDC for cylinder 6 in the back. Second thing, the FSM shows a way to check timing by counting the pins on the chain, it says 15 pins, BUT I counted 20. Something did not seem right and I counted all the pins, sure enough there are way more pins on the chain I have compared to the FSM, so some design change must of happened, if I set the sprockets according to the pins then the timing would not even be near the marks facing each other. So I left it as I had it with the cam sprocket at 180 degrees and assembled the engine the rest of the way.
Now it does not start, and I am quite depressed about it. I have fuel as I can smell it. I also have spark as I checked it. But I took the plug out of cylinder 2 and checked the compression and there is like no compression at all. So, I may check compression on all of them, but the largest question is could I have the timing off by a link? Would that would cause what I am experiencing? or anything else I can check to see what may be the cause?

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post #2 of 14 Old 06-07-2021, 04:14 PM
Mr. Puddles
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First thing that jumps out to me is zero compression. Even if your timing is 180 out you will still get compression ( bust spark would be on exhaust stroke). We need to ID why you dont have compression first.

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post #3 of 14 Old 06-07-2021, 04:41 PM Thread Starter
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Update: I measured the compression in all cylinders. I was off by one, its 3 that had no compression. So 2 and 6 have full compression (120). 1 is almost full (90), 3, 4 and 5 have almost none (<30). I assume this rules out timing, as I actually have good compression on two. I am thinking now the valves are bad I did not do anything with them. The head was resurfaced so I doubt its the gasket or head warp. Looks like I have to pull the head all over again and do a valve job? If I put my hand over the intake I get about two good "sucks" of air, so that lines up with the compression. It also "putts" while turning over like at least one or two may be firing.
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post #4 of 14 Old 06-07-2021, 06:27 PM
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you had the heads milled - often an issue for jeeps as the pushrods do not have any adjustment.
The way to handle would be using a compression leak down, shop air is feed into the cylinder and we can determine where the compression is escapng, I suspect the valves AND loosening the rocker arm I will bet the compression is sealed.

If correct we will need to et a shorter pushrod.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #5 of 14 Old 06-08-2021, 07:25 AM Thread Starter
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Originally Posted by jtec View Post
If correct we will need to get a shorter pushrod.
Oh.... well that makes sense now. The thought ran though my head that some of the rockers seemed tight and the valve was being pressed on even in TDC for that cylinder. I guess that is easy enough to test, but that leads me to two questions, where do you get push rods that are a few thousand's shorter or can I just put a steel washer that is a few thousand's thick under the fulcrum bolt? The guy that milled it said he had to mill quite a lot off, I thought the reason for hydraulic lifters was to account for that inconsistency and the lifter would adjust, that is why I did not think it would of been a issue. I can use a floating magnetic calibrator to determine the amount that I need to adjust for. Thanks for the tip, It is easy enough to pop the valve cover and check.
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post #6 of 14 Old 06-08-2021, 09:30 AM
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You can buy shorter pushrods or shim the rockers. The correct way is to use an adjustable pushrod to check your rocker arm geometry. You can google the procedure but basically you want the rocker tip to swipe across the middle of the valve stem as it cycles. This is critical for roller rockers and way less important for stock stamped steel rockers. Adjustable pushrods are not that expensive but you can also make one by cutting a stock pushrod in half and tapping the halves 1/4-20. Pushrods are widely available in 0.050" increments from about 5" up to 13". FWIW you don't need hardened pushrods in a stock application (without guide plates).

Hydraulic lifters typically have about 60 thousandths travel so you shoot for about 30 thousandths of preload. (but double check as some lifters are more than this) Mill off anything close to that and you just compress them solid.

Rocker shims: https://www.summitracing.com/search?...rocker%20shims

Pushrods: https://www.summitracing.com/search/...N=oiling%3ayes

Checking rocker geometry: https://www.lunatipower.com/how-to-v...train-geometry

You can make a test lifter by taking out the guts under the cup and shimming it at 30 thousandths preload.
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post #7 of 14 Old 06-08-2021, 10:42 AM
Mr. Puddles
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Quote:
Originally Posted by jtec View Post
you had the heads milled - often an issue for jeeps as the pushrods do not have any adjustment.
The way to handle would be using a compression leak down, shop air is feed into the cylinder and we can determine where the compression is escapng, I suspect the valves AND loosening the rocker arm I will bet the compression is sealed.

If correct we will need to et a shorter pushrod.
But why would he have compression in the first and last cylinders and not the middle? makes me question how flat that machined surface is

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2002 Dakota aka Winnie aka Mad Max
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Quote:
Originally Posted by kg6mov View Post
The 4.0 is dumb old tractor motor, itís too stupid to know itís supposed to die.
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post #8 of 14 Old 06-08-2021, 06:29 PM Thread Starter
kb9mfd
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Quote:
Originally Posted by zjosh93 View Post
You can buy shorter pushrods or shim the rockers. The correct way is to use an adjustable pushrod to check your rocker arm geometry. You can google the procedure but basically you want the rocker tip to swipe across the middle of the valve stem as it cycles. This is critical for roller rockers and way less important for stock stamped steel rockers. Adjustable pushrods are not that expensive but you can also make one by cutting a stock pushrod in half and tapping the halves 1/4-20. Pushrods are widely available in 0.050" increments from about 5" up to 13". FWIW you don't need hardened pushrods in a stock application (without guide plates).

Hydraulic lifters typically have about 60 thousandths travel so you shoot for about 30 thousandths of preload. (but double check as some lifters are more than this) Mill off anything close to that and you just compress them solid.

Rocker shims: https://www.summitracing.com/search?...rocker%20shims

Pushrods: https://www.summitracing.com/search/...N=oiling%3ayes

Checking rocker geometry: https://www.lunatipower.com/how-to-v...train-geometry

You can make a test lifter by taking out the guts under the cup and shimming it at 30 thousandths preload.
Thank you for the information, I should be able to get this taken care of with all that great info!
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post #9 of 14 Old 06-08-2021, 07:10 PM Thread Starter
kb9mfd
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Update: not good. I loosened the bolts on 3 so I know the valves are seating, but no go still only 30 psi. Looks like I will have to take it all apart again I was not at all planning on spending so much, Another round of gaskets..... and those bottom intake / exhaust bolts. I hate those bolts.
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post #10 of 14 Old 06-09-2021, 07:52 AM
zjosh93
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How much did you loosen the bolts? Loosen them too much and the intake valve won't open to let in air to compress. You probably would only need to loosen them about one turn to test. IMS the rocker bolts are 5/16-18 thread so each turn is 55 thousandths.
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post #11 of 14 Old 06-09-2021, 09:58 AM Thread Starter
kb9mfd
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Quote:
Originally Posted by zjosh93 View Post
How much did you loosen the bolts? Loosen them too much and the intake valve won't open to let in air to compress. You probably would only need to loosen them about one turn to test. IMS the rocker bolts are 5/16-18 thread so each turn is 55 thousandths.
I loosened them enough so that there was no play (the rocker would not wiggle back and forth) but it was not tight either. I watched them rock when I was turning it over, so I know it was opening and closing the valves.
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post #12 of 14 Old 06-09-2021, 12:22 PM Thread Starter
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Update: before I got too far, I made a jig up with my compression tester so I could compress the cylinder with my air compressor (it gets to 140 psi) and watch the gage and listen for leaks. Well, I removed the rockers for 2 and 3, and when I tested 3 the air was pouring out the intake, just as if I was shooting it in there. Well that says it, the intake on 3 was leaking like it was not even closed. I will have to take off the manifold to see if the exhaust leaks also, but I guess that concludes it. I was stupid and should of leak tested the valves. I also checked 2, I heard a small hiss but I am guessing that was the air leaking past the rings and it took like 2 or 3 seconds for the pressor to drop back to 0, so those must be ok. On 3 the pressure dropped to 0 immediately.

Update to the update. Sure enough, shine my mag light up the intake port and I can see a gap all around the valve. So I guess I am doing the valves.
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post #13 of 14 Old 06-10-2021, 07:47 AM
zjosh93
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I'm not sure what the valve clearance is like with the 4.0 stock cam, valves, and pistons. I'd guess it was a lot. But it would be a good idea to check that the valve didn't hit the piston. Whatever the machinist took off the head is amplified at the valve by the rocker ratio. Of course since it was a donor head it could have been some existing damage as well.

FWIW on your original timing chain question. There are two chain designs, 15 pin and 20 pin. The later engines use the 20 pin set and they are a direct swap so a lot of the companies only make the 20 pin set these days. See pics and https://www.cloyes.com/chrysler-dodg...4-clo-9-0736s/
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post #14 of 14 Old 06-11-2021, 09:50 AM Thread Starter
kb9mfd
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Quote:
Originally Posted by zjosh93 View Post
I'm not sure what the valve clearance is like with the 4.0 stock cam, valves, and pistons. I'd guess it was a lot. But it would be a good idea to check that the valve didn't hit the piston. Whatever the machinist took off the head is amplified at the valve by the rocker ratio. Of course since it was a donor head it could have been some existing damage as well.

FWIW on your original timing chain question. There are two chain designs, 15 pin and 20 pin. The later engines use the 20 pin set and they are a direct swap so a lot of the companies only make the 20 pin set these days.
Thanks, I did not see any damage or marks on the pistons or the valves, so they look like they are clearing, but there is carbon and crud on the valve seat so that would explain why its not closing all the way. I am working on that right now. I have the valves pulled and working on cleaning the head, then I will lap new valves, and if I cannot get them to seal I guess I will have to have those ground also. Thanks on the timing chain, I did have it correct then, I counted 20 pins, and I have found other threads that others have found that when the timing marks line up, its TDC Compression on #6 not #1.
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