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Reading on the forums here there was mention that less than 102lbs on a compression test would be a good indicator on why an engine would be hard to start. So I bought a compression tester, pulled the plugs and checked 'em. 75- 75- 70ish 40ish 75+ 75+
Can this thing run at 40-75 lbs? I thought that below 90 its not going to fire. Maybe I'm doing it wrong? The throttle's cracked open, all the plugs are out..
The truck does run, we've been having all sorts of fun with it.
Ideas?
Thanks!
-jim lee
Low compression
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Low compression
Carryall WC53 Blog : https://www.eskimo.com/~jimlee/Home/Car ... _Blog.html
Re: Low compression
hay jim
it sounds like your heading down the right path with removing all plugs and having the throttle wide open. the one 40 reading could be sticky rings or burnt/corroded valve.
here is a break down of how i do compression tests on my 37s. I get the best results from a hot motor (if she runs) first i remove coil wire(depends on how the truck is wired). remove all spark plugs(make sure the leads are out of the way). Connect battery charger (two may be required if your like me on 24v and don't have a 24v charger). I start @ 1 and work to 6 writing down each result as I get it. From the drivers side fender i hold the gauge with my left hand. then with my right engage the starter while holding the throttle open with a spare finger. Doing it by yourself, jumping in and out of the cab takes time and the readings may be skewed due to leaks (anyways how much do you trust the other guy holding the gauge while drinking a beer or worse playing on a cell phone). With the correct fitting selected(so no damage is done to any valve), i snug down the tester and crank for 5 seconds. if i think the seal is shat at the o ring I test with a little water and look for bubbles. flat heads are notorious for pitting around the plug. if i find my readings are low i add a little ATF to the cylinders to see if its the rings and re test. don't forget below the spark plug holes are valves. with the valve closed I insert a little hose to get the ATF to the cylinders(ATF is high in detergents and will free up most sticky rings). If the number have not come up i add thick oil and re test. If the numbers are good with guerrilla snot in the boars she could need a rebuild. If the numbers are still bad its the valves either way the fun begins by striping the head and having a good look.
keep us posted
it sounds like your heading down the right path with removing all plugs and having the throttle wide open. the one 40 reading could be sticky rings or burnt/corroded valve.
here is a break down of how i do compression tests on my 37s. I get the best results from a hot motor (if she runs) first i remove coil wire(depends on how the truck is wired). remove all spark plugs(make sure the leads are out of the way). Connect battery charger (two may be required if your like me on 24v and don't have a 24v charger). I start @ 1 and work to 6 writing down each result as I get it. From the drivers side fender i hold the gauge with my left hand. then with my right engage the starter while holding the throttle open with a spare finger. Doing it by yourself, jumping in and out of the cab takes time and the readings may be skewed due to leaks (anyways how much do you trust the other guy holding the gauge while drinking a beer or worse playing on a cell phone). With the correct fitting selected(so no damage is done to any valve), i snug down the tester and crank for 5 seconds. if i think the seal is shat at the o ring I test with a little water and look for bubbles. flat heads are notorious for pitting around the plug. if i find my readings are low i add a little ATF to the cylinders to see if its the rings and re test. don't forget below the spark plug holes are valves. with the valve closed I insert a little hose to get the ATF to the cylinders(ATF is high in detergents and will free up most sticky rings). If the number have not come up i add thick oil and re test. If the numbers are good with guerrilla snot in the boars she could need a rebuild. If the numbers are still bad its the valves either way the fun begins by striping the head and having a good look.
keep us posted
.............................. use it ...............
Re: Low compression
Well, things have changed.. Now it has one heck of a rod knock. So I guess the funs all over for the time being. I guess its time to build/rebuild an engine.
-jim lee
-jim lee
Carryall WC53 Blog : https://www.eskimo.com/~jimlee/Home/Car ... _Blog.html
Re: Low compression
Jim,
Sorry to hear about your bad news. These motors will "run" with pretty bad compression, so the numbers sound about right to me. The original motor in my truck had numbers similar to yours. it actually started pretty good and I drove it around a bit. I ran a compression test on it because I was getting ready to spend a bunch of money on the truck, and I wanted to be sure the motor was in good shape before dropping more money into it. My truck needed the correct carb, a new wiring harness, new fuel lines, and a complete charging system, not to mention paint and body work and tires. When I ran that compression test, I was heartbroke. The idea of adding at least a couple of grand on top of all that seemed hard to justify. For me I never was able to justify rebuilding the original motor. I ended up swapping in a fuel injected V8 and overdrive automatic trans. It got me a truck that i'm very happy with, and because I was able to do all of it myself, I did it cheaper than rebuilding the stock motor. In your case, your truck seems pretty complete. The cost of rebuilding that motor would be an investment in peace of mind. If you decide to have a shop do the work for you,I would spend some time picking the right shop. These engines aren't just like a small block chevy. I wouldn't want to pay some one to learn how to build one, I would want someone who's familiar with these old engines.
Good luck
Brett
Sorry to hear about your bad news. These motors will "run" with pretty bad compression, so the numbers sound about right to me. The original motor in my truck had numbers similar to yours. it actually started pretty good and I drove it around a bit. I ran a compression test on it because I was getting ready to spend a bunch of money on the truck, and I wanted to be sure the motor was in good shape before dropping more money into it. My truck needed the correct carb, a new wiring harness, new fuel lines, and a complete charging system, not to mention paint and body work and tires. When I ran that compression test, I was heartbroke. The idea of adding at least a couple of grand on top of all that seemed hard to justify. For me I never was able to justify rebuilding the original motor. I ended up swapping in a fuel injected V8 and overdrive automatic trans. It got me a truck that i'm very happy with, and because I was able to do all of it myself, I did it cheaper than rebuilding the stock motor. In your case, your truck seems pretty complete. The cost of rebuilding that motor would be an investment in peace of mind. If you decide to have a shop do the work for you,I would spend some time picking the right shop. These engines aren't just like a small block chevy. I wouldn't want to pay some one to learn how to build one, I would want someone who's familiar with these old engines.
Good luck
Brett
Re: Low compression
The plan is to rebuild it myself. I'll get a shop to do the machine work. I'm hoping we shut the poor thing down before we did too much damage. The wife was pressing for a modern engine swap so it could be used for road trips. I think it should be left stock. It is what it is and, like you said, its pretty complete. Its just that, -everything- needs a little work. I can see this project snowballing into something far larger.
For example, When I drive the thing I hear all the racket under the floor. I know its supposed to be loud, but I don't have the experience to know if what I'm hearing is ok or not. So it would be nice to look over the entire drive train while were at it. Then of course there's the iffy 24V wiring harness with PO's 12V hacks into it. Brakes, clutch.. Oh boy.
So I guess, we'll see..
At least I have a nice heated and dry place to work.
-jim lee
For example, When I drive the thing I hear all the racket under the floor. I know its supposed to be loud, but I don't have the experience to know if what I'm hearing is ok or not. So it would be nice to look over the entire drive train while were at it. Then of course there's the iffy 24V wiring harness with PO's 12V hacks into it. Brakes, clutch.. Oh boy.
So I guess, we'll see..
At least I have a nice heated and dry place to work.
-jim lee
Carryall WC53 Blog : https://www.eskimo.com/~jimlee/Home/Car ... _Blog.html
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MSeriesRebuild
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Re: Low compression
Just so you know for future reference; 100 PSI is border line, it will have low power and will possibly have some oil smoke going on under certain conditions.
90 PSI is unsatisfactory, likely will have some intermitent skipping going on at best.
Anything below 90 is a certain no go which you have already found out. While it may run or not, it isn't a good idea to do so, which again you have already found out.
Determining the reason for low readings is important and easy to do by adding oil through the plug holes and retesting. If you are lucky and valves are the cause, attend to it promptly, it will get more costly to repair quickly if you continue to run it. If it proves to be rings and cylinder wall wear issues, bite the bullet, it's rebuild time.
Don't mess around, do it first class the first time, bare minimum rebuilds cause 2 things. They cause extreme frustration when it doesn't take long for issues to start showing up again, and many times because of a short cut you end up with worse damage in critical areas the second time around, which is never a good thing.
Not sure of your meaning of "road trip"; but your wife is right about the engine swap if that is your intent. The 230 was never intended as a road trip engine by its very design. It is what it is; and your desired end use for the truck should determine what goes under the hood.
90 PSI is unsatisfactory, likely will have some intermitent skipping going on at best.
Anything below 90 is a certain no go which you have already found out. While it may run or not, it isn't a good idea to do so, which again you have already found out.
Determining the reason for low readings is important and easy to do by adding oil through the plug holes and retesting. If you are lucky and valves are the cause, attend to it promptly, it will get more costly to repair quickly if you continue to run it. If it proves to be rings and cylinder wall wear issues, bite the bullet, it's rebuild time.
Don't mess around, do it first class the first time, bare minimum rebuilds cause 2 things. They cause extreme frustration when it doesn't take long for issues to start showing up again, and many times because of a short cut you end up with worse damage in critical areas the second time around, which is never a good thing.
Not sure of your meaning of "road trip"; but your wife is right about the engine swap if that is your intent. The 230 was never intended as a road trip engine by its very design. It is what it is; and your desired end use for the truck should determine what goes under the hood.
Charles Talbert
www.mseriesrebuild.com
www.mseriesrebuild.com
Re: Low compression
Actually the original end use of the truck was my wife's idea. I come from what we'd call, a gas burning family. I spent my youth in and around all sorts of machinery being built, rebuilt or even invented. (I'm 9th of 9 kids) My wife's from a scholastic family and everything was always done by "professionals". You had things done, you didn't do them yourself. Anyway, she wanted me to get an older car so I could at least expose our kids to "wrenching". So, with more than her blessing I picked the M37 off the DPW classifieds. Everyone was ecstatic with the choice. They had imagined something boring, they never considered something fun like a "real" army truck.
Then they discovered mud & 4 wheel drive. {Chuckle}
Anyway. I Chatted with "52 M-42" on the phone a couple nights ago. He told me basically how engines come out of M37s. Then I did some reading of the tech. manuals. The plan is to pull the motor and, as you say, "do it right". I'll get the kids to help. If I can just get them to help pulling off the grill & fenders I'll count that as a victory. I might be able to push them as far as pulling out the motor? We'll see. They've never done anything like this so I have no idea how they will take to it.
I did let them set up a Facebook page on the truck. Anything to keep 'em interested. Oh and my Son, who names EVERYTHING, named it Theodore, and the name stuck. The plan is to let the kids rip this apart and post pictures for their friends along the way. I assume they will tire of being filthy and tired pretty quickly. At that point I'll probably finish the project.
At this point the plan is to pull the motor & gearbox, open things up and see what's going on inside. Possibly take "52 M-42" up on his offer to let us hear what one in working order should sound like.
As for modifying it? The plan is to rebuild it as it was. The only changes I want to do now is cleaning up some of the wiring hacks. It currently has a heater with a 12V fan that has its power tapped from between the batteries. I plan on adding a 24V-12V converter under the seat to power that. Then, "if" we are successful with the rebuild and "if" we get the driveline all dialed in with brakes and steering... Then -maybe- I'll bump the differentials up a tad. 45-50 mpg up to maybe 55-60 is as far as I'd want to go. This would allow us to take it off the island.
But for now, we'll see how doing an engine rebuild goes.
-jim lee
Then they discovered mud & 4 wheel drive. {Chuckle}
Anyway. I Chatted with "52 M-42" on the phone a couple nights ago. He told me basically how engines come out of M37s. Then I did some reading of the tech. manuals. The plan is to pull the motor and, as you say, "do it right". I'll get the kids to help. If I can just get them to help pulling off the grill & fenders I'll count that as a victory. I might be able to push them as far as pulling out the motor? We'll see. They've never done anything like this so I have no idea how they will take to it.
I did let them set up a Facebook page on the truck. Anything to keep 'em interested. Oh and my Son, who names EVERYTHING, named it Theodore, and the name stuck. The plan is to let the kids rip this apart and post pictures for their friends along the way. I assume they will tire of being filthy and tired pretty quickly. At that point I'll probably finish the project.
At this point the plan is to pull the motor & gearbox, open things up and see what's going on inside. Possibly take "52 M-42" up on his offer to let us hear what one in working order should sound like.
As for modifying it? The plan is to rebuild it as it was. The only changes I want to do now is cleaning up some of the wiring hacks. It currently has a heater with a 12V fan that has its power tapped from between the batteries. I plan on adding a 24V-12V converter under the seat to power that. Then, "if" we are successful with the rebuild and "if" we get the driveline all dialed in with brakes and steering... Then -maybe- I'll bump the differentials up a tad. 45-50 mpg up to maybe 55-60 is as far as I'd want to go. This would allow us to take it off the island.
But for now, we'll see how doing an engine rebuild goes.
-jim lee
Carryall WC53 Blog : https://www.eskimo.com/~jimlee/Home/Car ... _Blog.html
Re: Low compression
Jim you are welcome to see more than just how it sounds. You are welcome to drive it and crawl all over it to see how things are routed, attached, wired and plumbed.
Whenever you are ready we can set up a time. Bring the wife and kids too, if you want.
52 M-42
Whenever you are ready we can set up a time. Bring the wife and kids too, if you want.
52 M-42
Re: Low compression
Theodore is a great looking truck keep us posted on your progress
.............................. use it ...............
Re: Low compression
Hello Jim, I also have just suffered the heartbreak of low compression today. I have not been using my '53 M37 much in the past 4 years but I do start it on occasion. When I got the truck 6 years ago I did a compression test and the lowest cylinder was 112, I was very happy about that, today it would not run without choke, after checking everything I summoned up some courage to do another compression test and and got very depressed, 60,55,60, etc. I broke out my differential pressure tester that I used on aircraft engines, this pressurizes each cylinder and measures how much is leaking from each one on the compression stroke, I pimped in 80 psi and could hear air coming out of the oil filler tube and each cylinder is only holding 40 psi, that is a 40 psi differential and should only be less than 10 (at least on aircraft cylinders). I did not hear anything coming out of the intake or exhaust so the valves are likely good. This was a shock to say the least, I have a parts truck that did the same thing a few years ago and removed the head to see beautiful cylinders with no top ridges, the valves are good so it's a mystery. I'm going to take the head off of my now sick "good" truck and check out the situation.
I wonder if the oil I put into the cylinders after the last time I ran it caused the rings to stick. Just a thought. Any way good luck to the both of us and our
"projects"
I wonder if the oil I put into the cylinders after the last time I ran it caused the rings to stick. Just a thought. Any way good luck to the both of us and our
"projects"
Re: Low compression
This is my engine that recently failed compression test (about 60 psi in all cylinders). The cylinders to me look good with no detectable top ridge , the valves seat well so I figure stuck rings, I plan to pop out a piston and test my theory. This was an engine that had great compression 5 years ago when I bought it, It did sit in my garage for most of that time but I did start and warm it up several times a year so I'm a bit puzzled why this happened. Any experienced input would be greatly appreciated.
Thanks
Thanks
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MSeriesRebuild
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Re: Low compression
Look closely at exhaust valves. Is there a hard black buildup under the heads? Your description of activity over the past 5 years sets up the perfect scenario for stale gas to do its thing. How often did you renew the fuel in the tank with fresh gas? Did gas sit there in the tank for months between start ups or did you put in fresh gas each time you startred it?
Charles Talbert
www.mseriesrebuild.com
www.mseriesrebuild.com
Re: Low compression
Good to hear from you Charles,
To start it up I always used a gravity tank setup with fresh gas each time, I also used a bit of Marvel oil mixed in. The really strange thing is that I have the same problem with a parts truck that had a nicely running engine until about a year ago, nice bores, good valves and 60 psi pressure. When I pressurize the cylinders on either truck you can hear and feel the air coming out of the oil filler tube, none coming out of the intake, exhaust or into the coolant. Could the rings be collapsed? Thanks again for your time.
Bob
To start it up I always used a gravity tank setup with fresh gas each time, I also used a bit of Marvel oil mixed in. The really strange thing is that I have the same problem with a parts truck that had a nicely running engine until about a year ago, nice bores, good valves and 60 psi pressure. When I pressurize the cylinders on either truck you can hear and feel the air coming out of the oil filler tube, none coming out of the intake, exhaust or into the coolant. Could the rings be collapsed? Thanks again for your time.
Bob
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MSeriesRebuild
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Re: Low compression
Impossible to know exactly, but sounds like rings may be stuck in the grooves. Since you have the head off, I'd spray some Kroil penetrating oil onto the cylinder walls and let it seep down on the rings. Do that several times, then rotate the engine stopping at a different spot each time. If you could do this several times a day over a few days, rings should free up if that is the issue.greencom wrote:Good to hear from you Charles,
To start it up I always used a gravity tank setup with fresh gas each time, I also used a bit of Marvel oil mixed in. The really strange thing is that I have the same problem with a parts truck that had a nicely running engine until about a year ago, nice bores, good valves and 60 psi pressure. When I pressurize the cylinders on either truck you can hear and feel the air coming out of the oil filler tube, none coming out of the intake, exhaust or into the coolant. Could the rings be collapsed? Thanks again for your time.
Bob
Charles Talbert
www.mseriesrebuild.com
www.mseriesrebuild.com
Re: Low compression
Charles,
I will give it a try, if that doesn't work I guess the next step will be to remove a piston. I had a Model A Ford engine that had a decent bore, I removed the piston and found the rings so stuck in the grooves they had to be removed in pieces, perhaps this is a similar case. As soon as my back feels better I'm going back under the hood (lifting the head off pulled something), I'm getting old. Thanks ever so much.
Bob R
I will give it a try, if that doesn't work I guess the next step will be to remove a piston. I had a Model A Ford engine that had a decent bore, I removed the piston and found the rings so stuck in the grooves they had to be removed in pieces, perhaps this is a similar case. As soon as my back feels better I'm going back under the hood (lifting the head off pulled something), I'm getting old. Thanks ever so much.
Bob R