Problem shooting on my m37

[Jesse19rap]

Hi Everyone,

1st issue
I'm a Noob here and to the hobby for that matter and have a couple amatuer questions. I bought a 1962 m37 about a month ago. Recently I've been able to get it running pretty well. She will sit there and idle, rev in neutral for as long as i want. Every once in a while i will drive it around our farm and this is where the problems start. I parked it after driving it for 10 minutes and once turned off it will NOT restart for hours. I checked the distributor and it seems to have a weaker spark when it's hot than during the initial start-up. When i took the dist. cover off i realized the black rotor cap is really loose. I can twist it a good half inch without the "post" moving. On other vehicles theses are always tight. Could that be the problem? Any ideas where to look. It seems to be heat related.

2nd issue
I'm not sure if these two problems are related but who knows. I changed the oil and flushed the brake lines this week and realized the oil was extremely thin. Upon further review i realized there was gas in the oil. I finished the oil change and fired it up hoping that the problem didn't still exist. I drove it for another 10 minute spell then it died on me in the middle of the field. To my dismay the gas had again went into the oil. The truck had been sitting outside for about two years and I think things are seized up. Any ideas where to look for this issue. Any and all advice will be greatly appreciated as I am still learning the simplest of things on this truck.

On a positive note my manuals should come in today!

Thanks ~Jesse

 

[WillWagner]

The rotor should be tight on the distributor shaft. It is normal to be able to give the rotor a bit of a twist and have it spring back, that is the advance mechanisim.

Fuel in the oil can be caused by a leaking diaphragm in the fuel pump.

 

[Buz]

You need a new fuel pump or rebuild the one you have. I had an M37 do this years ago, the old got so thin it almost ruined the engine before I realized it.

 

[1958 M274]

1st issue... Weak or no spark when hot, but runs ok cold? It's likely your ignition coil is failing when it gets hot. I'd try replacing it, along with the points and condenser.

WillWagner covered the play in the distributor rotor.

If you think you still have sufficient spark for it to run when it gets hot, one other thing to check is the rubber fuel hoses. I bought a truck one time that would start and run for a few minutes, then die. Let it sit a while and it would start and run for a few more minutes, and die. It was a fuel starvation issue, and one of the rubber fuel hoses has swollen up inside and was restricting the fuel flow. It looked ok on the outside.

2nd issue... As others have said, your fuel pump diaphragm is likely leaking gas into the oil. Rebuild or replace.

Good luck!

 

[nattieleather]

Both issues may be the fuel pump. It sounds like when cold it pumps fuel fine as the motor warms up the pump starts to fail. Fix the fuel pump problem and then check from there. Gas could be getting into the motor via piston rings, but it sounds to me like what others have said the fuel pump is your big problem.

 

[tuckered]

for the fuel pump.

Check that distributor for cracks. Had a vehicle that when the engine got warm, a crack in the cap would "suck in moisture", had problems until I replace the cap, cleaned everything on the inside. Worked perfectly after that.

I could only assume that the change in engine temp warmed the distributor cap. Then when the cap cooled, moisture condensed inside, grounding out the spark. Just saying, don't overlook the inside area of the crack. Wish you best of luck.

 

[beltfedonly]

M37

Replace the coil, it is inside the distributor. The diaphram in the fuel pump is leaking fuel into your oil pan. Have the pump rebuilt.

 

[135gmc]

I agree. Replace the fuel pump and the coil. Anotehr problem is that these trucks have problems with fuel percolation - that's when the fuel in your gas line between the pump and the carb gets too hot. It's not vapor lock, it's a fuel line problem. The cure is to be sure that the shield between the exhaust pipe & manifold and the fuel line is installed and is intact. I also added insulation to my fuel line as well. Also, be sure that the manifold heat valve is totally closed. It's manually set, and 99% of the time, you can leave it closed. Also, try to never run winter gas in the summer - winter gas is a bit more volatile so it will run better in the winter, but it will really cause problems in the summer.

 

[Jesse19rap]

Great stuff guys. I appreciate all the info. I will try these recommendations. Hopefully they will solve my issues!

 

[MDSA]

Because the m37 coil is in the distributor, it gets hot if not properly ventilated. Air lines should be in place to form a draft of cool air. Two thin lines go from the air breather throat to the base of the distributor, making a constant cycle of air.

 

[morbius]

Hey there

I have a question for the group. I recently purchased a 53 M37. I would liek to replace the watertight ignition with a "civi" 12v style. Is there a drop in alternative?

THANKS!!!!!

 

[135gmc]

When I've seen this done, I think they just tracked down a distributor used on the civilian version of the 216 engine. Add new plug wires and the correct civilian plugs and you should be OK

 

[morbius]

That would sure be cool - I will look into it a bit... I did see a couple threads about changing the oil pump too.

 

[WarrenD]

IIRC, the civie distributor doesn't have the correct end to run the oil pump. What seems to be more popular is converting the old point system to electronic.

 

[morbius]

yea - I did see that about the oil pump - it is nice to hear though instead of just read under a photo - good confirmation. I am most interested in getting a distributor that is not a watertight deal - so hard and ecspensive to maintain. And i want a 12vdc system so i can do signals for road driving. We purchased the M37 to take cruises on warm summer days. Its life now will get easy. I am actually considering a motor swap to a 350 with an auto tranny - does anyone have any tips or hints on that?

 

[Jesse19rap]

So i by-passed the gas pump because i wasn't sure if the gas tank was clean and made a small tank connected directly to the carb. The gas is still getting into the oil. Is there an adjustment or needle valve in these carbs? Any ideas where to look since the pump is no longer in the mix and the issue still exists?

 

[nattieleather]

Ok so the truck still cuts out after it warms up? The fuel getting into the oil to me sounds like bad rings. Could be a combo of to much fuel from the carb and bad rings. I'm sure someone with more hands on knowledge of the motor than me will post the answer you seek.

 

[WillWagner]

Take a compression test. Rings seal combustion gasses but not liquids in small amounts. If the float level is too high or the floats/valve is stuck or has crap in it, fuel can overflow the float bowl and end up in a cylinder, then in the pan. When it runs, does it puff black smoke out the tailpipe?

 

[Jesse19rap]

No, no black smoke at all, even when it starts their is only a small amount of white smoke.

 

[SteveKuhn]

You're having precisely the same stallout/no start problem I am with mine. Along with all the other stuff mentioned (which are on my list), take a close look at the fuel lines and make sure there are no kinks if they're metal. I found one in mine that could act like the collapsed rubber ones described above. It's coming up from the fuel pump to the carb. Particularly vulnerable because it's in a hot area. It's getting replaced.

Steve


Steve