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my m37 is old and worn out, I decided to grind and lap the valves in to see if it would start better. I got it back together and no improvement but now when it gets hot it misses and dies and won't restart till cold. I cleaned the points and found a bunch of water in there, checked and adjusted the float level a bit, timing is around 4* atdc. thought maybe the valves were to tight so I checked all them and set them at .10I .13E cold. the little tab broke off the heat riser when I had the manifold off. It has always just flopped around, would that cause the truck to shut right down like that?
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If the heat riser is stuck in full (winter ) it may be cooking the carburetor.
How is your compression ? You probably allready know how to test if you have leaky valves or rings.
Squirt a tablespoon full of engine oil in the sparkplug hole , run a compression test. If the compression comes up a good bit, you have bad rings, if it does not change much at all its probably weak valves.
Try not to do too many things at the same time. You will start getting lost. -
compression is poor, 90-100# truck doesn't burn any oil. I did the valves but the guides were pretty worn and I didn't replace them. some of the valves didn't have much meat left on them after I ground them in the lathe. I just want it to run so I can get it back to work. I am about at the end of my patience with it and may be selling it shortly if anybody is looking for one in western PA.Comment
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100 pounds is not toooooo bad. Mine had only around 85 and it ran , hard to start but it would rev up ok and drive ok on flat ground. No hills please.
Not running well after good and hot sounds like you are cooking the carb. Or maybe cooking the fuel pump. There should be a heat shield on to keep heat from the manifold off it.Comment
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I wasted the better part of my day working on it. I fixed the heat riser. it stops very abruptly when it gets to hot. it is very repeatable. let it get hot and it stops. let it cool off and it starts right up.
I let it idle until it died and then checked fuel flow, carb and base were cool to the touch from the air flowing through it. fuel pump flowing nicely with good pressure. spark looked a bit weak but was still present. I changed the condenser and let it cool off started it and it died again. changed the timeing to 5* btdc and let it cool off started it and it died. I am wondering if it is the coil. that would really tick me off beause I just bought that coil like 2 years ago from Midwest. don't remember the price but it was not cheap.Comment
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If you go to a good electronics place, maybe even a good Radio Shack they should have cans of spray cool. We used it when I was working in the electronics field for the space program before it was cut back to the bone.
Anyway its great stuff for finding thermal problems. Engine cuts out, spray the coil or what ever with the cool spray and if it starts back up ,,bingo bad whatever you sprayed it on.
You could have a breathing coil, it gets hot,,,off, it cools off ,,On again. The spray stuff will let you know right away.Comment
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well I came in the house last night and told the wife I am done with the truck! got up today it's raining so I am back out in the garage. I ran it till hot and it shut down. then took hot compression readings to see if the valves were sticking open or something. over 90# and even on all cyl's. spark was just a good hot as it looked cold so I tore the carb apart and cleaned it all out. then I made sure the intake bolts were tight. restarted it and it died when hot again. pulled the dist apart and checked the coil continuity hot and cold by heating it with a heat gun. cleaned the points and put some insulation varnish on the stud where the points attach to the condensor and coil. started and reset my timeing to 5* btdc at a low idle. sort of touchy because there is no vacuume advance to disconnect.
coil readings
+to casing (hot 1.2Mohm) (cold 8.7Mohm)
+ to - (hot 12.5ohm) (cold 11.5 ohm)
+ to high tension lead (hot 12.13 kohm) (cold 11.67K ohm)
seems kind of fishey that the resistance to casing goes down as I heat the coil up but 1.2M ohm is still pretty high and I do have good spark when it is shut down. I am pretty stumped. I have fuel compression and spark and It just dies. I am done with this truck! but I will prolly be working on it tommorw lol.Comment
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The low compression is hurting you for sure. Shutting down when hot is a classic symptom of the coil breaking down. Is the vent system on your distributor hooked up and functioning correctly? If not, fix it. That will cause it to stall and will eventually kill the coil. The timing should be set at 4 degrees BEFORE TDC. Are the shaft bushings in the distributor worn out, any side wise loose motion in the shaft when moved by hand is NOT GOOD; especially if you are running a points system.
Bottom line is this, if replacing the coil doesn't do anything for it; it is OVER; you will never have a decent runner until you bite the bullet and rebuild that engine the right way, without cutting corners in the process. 100 PSI is only border line run-not run, between 90 and 100, you will have intermittent skipping and stalling just like you describe. The valve situation you described is also terrible and will not heal itself. I'm telling you straight up, you can spend time and $$ on tuning every day, you won't accomplish anything by it except further frustration.Comment
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new coil came in the mail. showed no continuity to ground proving the old one was bad. installed and truck runs good now. I know it's been beat to death and don't mean to start an argument but i am going to take the silly little 3/16 lines off the dist and see if this coil lasts longer. i think they are doing more harm than good. trapping moisture so it can't evaporate out. if that doesn't do it i am going to run wires out through those holes and relocate my coil to the fender or fire wall where it can stay cool. i will let you guys know if it poops out in a few years. plus if it is external i can use a 12v coil with a resistor in line with it. i know the pureist's hate me but nobody wants to buy the truck from me and save it from my "farmer" fixes. lol.Comment
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Well I'm not a purest, and I certainly don't hate you. If I hated you, I wouldn't have offered any suggestion as the coil breaking down being a likely cause for your problem.
I'll just say this, then leave it with you. If you are intent on defying common sense and disabling that silly little vent system, your best bet is to go ahead and take the coil out of the enclosed housing now. The chances of it having a decent life span will be much improved.Comment
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Charles, have you noticed any type of longevity difference between the aftermarket 24 volt coils and NOS coils?1967 W200.aka.Hank
1946 WDX.aka.Shorty
2012 Ram 2500 PowerWagon.aka Ollie
Life is easier in a lower gear.Comment
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That is a tough comparison to make since it has been years since NOS coils were around in quantity. Fact is you got bad ones on occasion when NOS was all there was, an occasional bad one still surfaces now. I guess I'd say it this way, in comparison to the number of aftermarket coils that are out there these days, they have a really good track record in my opinion. As far as longevity is concerned, I can't say I've seen any difference to speak of. The majority of bad ones we see have always been due to the vent tubes being removed, air not circulating because of wrong fittings, kinked tubing, etc., or the ignition switch being accidentally left on for extended periods of time. Human error is by far the bigger reason for failed coils.Originally posted by Iowanogre View PostComment
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I do appreciate your help Charles, just kidding around some. usually doesn't come out right in print. anyway I just can't fathom how those tiny little lines with about the same intensity of a mouse breathing could possibly remove enough BTU's of heat from a hot coil on a hot block with hot air from the radiator washing over it. here is My theory on my coil failure problem. I remember being told at some point that it is hard on coils to check spark by just holding the coil wire and watching the big zap it makes. I had a lot of trouble with my distributor when I got this truck and put new seals and bushings in it, and a new cap and rotor. I had a lot of clearance issues with the cap being too high and tried it with and without the rubber washers under it. long story short I wonder if it's still not right and is making the coil work overtime to jump the gap between the rotor and cap every time it fires.Comment
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Impossible questions for me to answer unless I had the whole distributor here so we could check out every aspect of it.Originally posted by gusbratz View PostComment
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