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What have I done? |
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smfulle 
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Sponsor Member Joined: 16 Sep. 2010 Location: Ogden, Utah Status: Offline Points: 6140 |
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 Topic: What have I done?Posted: 16 Nov. 2015 at 6:27pm |
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I've got my rebuilt engine all installed but I can't get it to start. Triple checked the timing, the fuel, the spark, the valve clearance. All good.
The compression on new rings is only 60. Is that ok for new rings that have not be broken in yet? I've been wracking my brain to remember all the processes I went through and where I could have made a mistake. Would a tooth off on the timing gear give you a compression reading of 60 and a no start? I had a little trouble lining up the marks because of the angle on the gears, but I thought I had them lined up right. It's the only thing I can't really see in my head that I double checked. It feels like it wants to start but needs a little faster spin. I think I might try a pull start before I start pulling things apart.
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eestes1
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Posted: 16 Nov. 2015 at 7:56pm |
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The best mechanics I know, and I am certainly not one of them, usually say its probably something simple. I hope it is, and good luck.
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Rick Estes
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cpt logger
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Joined: 23 Sep. 2012 Location: Western Colorad Status: Offline Points: 3039 |
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Posted: 16 Nov. 2015 at 10:32pm |
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Stan, No, a compression on new rings of only 60 is not correct. It should be at least 100. It may start with that low of compression, but you will be unhappy with the lack of power, & the fuel consumption.
Yes a tooth off on the valve timing will do this. If this is the problem you will have to pull the gear off of the camshaft. Use a puller to remove it & use a long bolt to pull it back on. do not use a hammer on the cam shaft. Doing so may push the Hubbard plug out of the back of the camshaft bore. That will cause a massive oil leak. Not good. I recommend that you find & fix the compression issue before you try to pull start this rig. Doing so may cause some damage that it does not have now. IHTH, Cpt Logger. |
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Red Willy
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Joined: 18 Mar. 2014 Location: Lake Villa IL Status: Offline Points: 512 |
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Posted: 16 Nov. 2015 at 11:11pm |
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Stan, I drove mine for two years after after a full restoration and was never happy with the performance, it just didn't run the way I felt it should. I had compression of 70 or so on all four cylinders but I could get the vacuum to hold steady at around 19 or so. In the back of my mind I always questioned myself on the valve timing for the same reasons you stated. I finally pulled the front cover and sure enough I was a tooth off. It runs much better now but I have not taken a compression check since redoing the timing. I am afraid of what I might find
 If it is a timing issue you can probably rotate the distrtibutor to get it to start, but as previously stated, I would recommend diagnosing the low compression prior to starting. |
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Glen
49 CJ3A |
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Mark W.
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Posted: 17 Nov. 2015 at 12:21am |
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Keep in mind that if you have been trying to get the engine to start a bunch and it is not you have now wiped all the assembly lube off the cylinder walls and its running on pretty dry rings. You will want to pour some Motor oil in the cylinders to get a little lube back on the wall before you try to start it again. DO the timing gear check and if need be adjust the timing (I too think this is a likely cause) but once you button it back up pour a couple tablespoons of oil in each plug hole and rotate the crank a couple times with a breaker bar to get some lube on the cylinder walls. Dragging new rings on dry walls is not a god thing.
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Chug A Lug
1948 2A Body Customized 1949 3A W/S 1957 CJ5 Frame Modified Late 50's 134L 9.25"clutch T90A D18 (1.25") D44/30 flanged E-Locker D25 5.38 Since 1962 |
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smfulle
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Posted: 17 Nov. 2015 at 2:31am |
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Well, I couldn't stand not knowing so I pulled the radiator and the timing cover.
It's good to know that I did it right, but now I don't know what to check next. I guess I'll recheck my recheck on the valve lash while I wait for the special order timing cover gasket to come in.  |
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WillyBill
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Posted: 17 Nov. 2015 at 3:20am |
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Could the valves not be seating well? My rebuilder did not have a machine tall enough to do valve seat work on an L head so I took the block to a shop that could do the valve seat work. Then I took it back to my rebuilder. He used a device to pull a vacuum to check the valve seal and was not pleased with the results. He lapped the valve seats and rechecked and the valves sealed much better.
What do you all think? |
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1947 CJ2A #146428
1947 CJ2A #103567 |
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p3ferris
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Posted: 17 Nov. 2015 at 3:41am |
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That was my thought WillyBill
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Ed
cj2a lefty |
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smfulle
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Posted: 17 Nov. 2015 at 4:04am |
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I suppose that could be. I don't want that to be the answer because it means pulling everything apart again and hauling it over to the machine shop.
A couple of other questions: Could a slow turning starter give a false low reading on the compression gauge? On the later model L-134 with the timing pointer on the timing cover and the notch in the pulley, is the notch TDC or is it the 5 BTDC required for ignition timing? I set all the valves at .016. Some have said they should be .014, but even if that is the case, more valve lash shouldn't cause lost compression, should it? I thought tight valve lash would keep valves open too long and cause lost compression but more lash would keep valves closed longer for higher compression. Thanks for the suggestions so far. |
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pjensen641
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Posted: 17 Nov. 2015 at 6:29am |
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Maybe get a leak down checker or make one. Should help you see if its in the valves or the rings.
Slow starter or not holding WOT does affect compression.
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Joe DeYoung
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Posted: 17 Nov. 2015 at 1:35pm |
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Stan,
A couple thoughts on your compression problem: 1) When you rebuilt the engine, did you check the adjustment screw on the tappets for cratering? If the valve contact area on the screw is cratered, you will not be able to set the valve lash correctly as the valve stem sits down in the screw... so you don't get an accurate feeler gauge reading. 2) did you open the throttle to check compression?
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Joe DeYoung
to many jeeps, parts, and accessories to list here, but apparently enough to keep me in trouble with my wife. |
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JTB
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Posted: 17 Nov. 2015 at 1:59pm |
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Please explain the role of open throttle in compression testing...
Always more to learn JTB
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The problem with socialism is that you evenually will run out of other people's money to take
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smfulle
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Posted: 17 Nov. 2015 at 3:57pm |
1. I looked at the screws and didn't feel any wear. I did not check them with a straight edge or anything like that. I wasn't too worried because this engine has very little wear. I spun a rod bearing due to oil starvation. The oil pickup screen was practically plugged off. 2. I did NOT do the compression check with WOT. This is the first that I have heard of that. More proof that I am an amateur. I did have all the plugs out. Once I get the front cover back on I'll try it again with the WOT and see if that makes a difference. |
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Becca
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Posted: 17 Nov. 2015 at 6:03pm |
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Did you check the cylinder bore to make sure it is perfectly round? And honed?
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1947 Willys CJ-2A
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smfulle
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Posted: 17 Nov. 2015 at 6:33pm |
Machine shop did that for me.
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Leonidas
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Posted: 17 Nov. 2015 at 7:34pm |
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There is no need to pull the camshaft drive cover to check the camshaft timing.
All you need to do is pulling the tappet cover and make sure the flywheel marks are visible, or the marks on the V-pulley. When the timing is right, the valves from the cylinder that change from exhaust stroke to inlet stroke must overlap while the TDC mark is passing by. If the overlap from the valves happens before or after the TDC mark is lining up, the timing is off. Sorry this came to late for you. For your non starting issue, the compression you have is low, but the engine should and will start. I dont know what you have checked so far, but usually when an engine get started for the first time it get flooded. I would check the voltage on the battery when you hit the starter. If there is too much voltage drop, the coil wont deliver a good spark. As you will throttle a lot while attempting to start, the engine get flooded as the acelerator pump in the carb does squirt fuel in the manifold each and every time you push the gas pedal. It is a good idea to have 2 battery's conected...one to the starter, and another one to the ignition system. That way you are sure the ignition does not suffer voltage drop from the starter sucking all the amps. Am pretty sure that with a good battery and propper crank speed the compression will be good on your rebuild engine. But first I would get it to run. Good luck, Luc |
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jeeps are great !
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a4cj2a77
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Posted: 18 Nov. 2015 at 6:10am |
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I would oil down the cyls with oil and recheck comp with throttle open and a hot battery, if this does nothing a leak down is in order to verify if there is leakage at valves or rings. Are the rings staggered, end gaps checked, bored to spec. Seat and valve work correct? I assume the machine shop did this for you. Wide valves will only help your issue. If your comp is even across all cyls, this would indicate that your issue is systemic like timing, dry rings. Is your compression gauge reading correctly. Sorry about the ramblings, just thinking out loud
Phil
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pjensen641
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Posted: 18 Nov. 2015 at 8:14pm |
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Compression is always done with a full battery, good starter and WOT. If you leave the throttle closed, the full intake cycle will not be able to fill the cylinder. This is, after all, how the engine regulates speed. Less air in the cyl, less compression in terms of PSI.
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Joe DeYoung wrote: