1953 M37 Carb Flooding. Assistance needed.

[RAT]

What has happened with this?

 

[highfavor1004]

rebuild one myself

 

[grimlock97]

Sorry, I haven't updated the post, I have just about pretty much given up on the m37, I have a friend that keeps saying he's going to come look at it but hasn't and he's a mechanic for Alabama Power and works on diesel and carbureted engines day in and day out, I was hoping he could figure it out, I have completely removed the electric fuel pump and installed the rebuilt original pump, it pumps gas great, the vacuum lines were missing so I put one vacuum line to the intake hoping it would help and it still just floods the intake, I have to change the oil often when I work on it which is less and less lately, I bought another m37 for parts and have the winch to put on this one but doesn't do much good just sitting there, if my mechanic friend can't figure it out I'll let everyone know

 

[GUNNY 155]

What ever it is will need to go into the book of odd but true stories. In the world of automotive engineering these vehicles are entry level so you would think with all of us out there helping we would have hit on something. One thing for sure is it doesn't make any sense.

 

[grimlock97]

Yes, it is very odd, one thing I just noticed today though is I'm not sure this engine is an mv, I tried taking the dipstick tube off my parts m37 and the 245 in the good m37 looks like it has a press on tube instead of the screw in, I'm not sure if that would have anything to do with it not liking the etw1 carb or not, it has the correct fuel pump but I'm noticing subtle differences between the two motors, the oil filter also looks a little different. Thanks again for the help, might be time for it to go on the auction block

 

[RAT]

Let us know before you do something like that. . . . . .

 

[cjcottrill]

I don't know if it will help, but mine has a temperamental carb as well. Worse when the engine is hot. I have found that when starting it I can't touch the throttle. With the engine cold I pull the choke and push the starter button. If I touch the throttle before it starts it will flood. When warm, don't use the choke. Once it starts it is fine. If I touch the throttle before it "hits" it is done for. I drive it regularly without issues, just had to learn the idiosyncrasies. I do have to turn in the fuel screw a quarter turn every few trips. It backs off some- must need a new spring on the screw. I have grown quite adept at the heel & toe starting technique. Don't give up, you will get it figured out -- it will be worth it.

 

[big1096]

Call Vintage Power Wagons and tell them what problems you're having. Yens has been a wealth of knowledge for us while chasing some problems with the M37. (641) 472-4665. And they have lots of parts if you should need them. Don't give up yet!

And +1 on letting us know before you put the project out there for sale.

 

[grimlock97]

That's where the new / rebuilt carburetor came from and I told them what was going on with the one I rebuilt and they were at a loss for what could be causing it as well, I usually try not to touch the throttle when trying to start, it still fires off ether without a problem, but quickly floods out, I do need to see if there is some adjustment in the throttle though, because my throttle lever pushes out when I do hit the gas, it seems kind of tight up front.

 

[big1096]

One other thing to check is the clip that holds the float down. We had a clip in one of the carbs that wasn't going all the way down and it was allowing the float to move up and hit the bottom of the top plate. We had to adjust the clip to make it hold the float down in the proper place.

We still have a problem with a low speed miss and low vacuum. We're going to do a valve adjustment next. The engine rebuild has about 500 miles on it, so it's probably due.

Best of luck.

Jim

 

[RAT]

Any news, find a fix for this?

 

[Brutalowner]

Any news, find a fix for this?

Yes, any new news? I have the same issues. Excellent thread!

 

[Roger Friedrich]

I would like to just put this out there about something I encountered while overhauling my M37. While I was checking things on my engine when I found a carbon build up in the pvc plumbing especially in the area of the manifold were the plumbing screws in. Could the lack of no air flow from the crank case cause a part of the problem

Also I was wondering about if the engine doesn't have enough compression to pull the gas vapors into the cylinders would that cause some of the problem? My engine won't start on it own with out ether and the main cause was low compression. So my question to the experts is if there isn't enough vacuum to pull the gas vapors into the engine would the gas pool at the base of the carb?

Just a thought??

 

[RAT]

If the engine has so little vacuum it will not pull the vapors into the cylinders it sure won't be able to pull fuel from the bowl.
We have to be missing something.

 

[Brutalowner]

Mine runs great on cold start up, but about 30 seconds in, it begins to load up, and ends up stalling. During many experiments, I have removed the pcv and put a vacuum cap over the nipple. When it stalls, I can pull the cap off and fuel runs out. So bad it washes off the top of the front diff! I've had the carb apart 7 or 8 times. Set the float level on the engine with the top off the carb and the electric fuel pump running to verify needle and seat operation and actual fuel level.
The truck was running great, then one day decided to pull this flooding trick. Don't know what to try next. Spark is great, timing is at TDC, plugged the vacuum line to the pump, removed the pcv, all trying to eliminate other causes. What's next?

 

[o1951]

No experience with your specific carb.
I can tell you PCV will not cause flooding, in fact removing it will cause engine to run a bit rich. The carb mixture was calibrated to include air introduced by the PCV. Without that air, the mixture will be a little rich.

That is a very simple carb. I would be concentrating on 2 areas, fuel pressure and needle not closing against seat. I would start with the easiest first. To eliminate an electric fuel pump defect, I would tap a pressure gauge with some fuel hose into fuel line at carb. Mount gauge where you can see it, and note fuel pressure when this happens. If it is ok, then you can concentrate on carb.

If you are using ethanol laced gas, it is possible that pieces of crud are occasionally loosening up and getting stuck between needle and seat, preventing proper closing. If in doubt, clean up carb and install an inline filter in fuel line just before carb.
I have had another issue with ethanol gas. The rebuild kits I got had Viton or similar elastomer tipped needles. After a time, something in ethanol gas caused the tip to deteriorate, and the needle would no longer seal. I wound up finding an old stainless steel needle and brass seat, and used that.

I have seen old floats get tiny leaks and ride too low in the gasoline, causing flooding. If you shake the float and hear noise, it is no good. Another way to check float is to submerge it in a container of hot water, to slightly expand the air inside and put slight pressure on float. If you see tiny bubbles coming out, you have a leaky float.

I have seen very high mileage carbs with worn float arm pivots. With enough wear, the float can contact the side of the carb in operation. It then hangs up, causing flooding. LIGHTLY push on float assembly. If there is enough slop for it to touch sides of carb, that has to be fixed.

 

[Brutalowner]

Thanks for the input o1951. He are more details of what I've done:
We removed the PCV assy to eliminate a possibility for it being a vacuum leak, as in the check valve staying open. We also plugged the vacuum line fitting on the intake to eliminate that system as well, with the intent to start re-installing each system one at a time in the event that it started running like it should.

I rebuilt the carb with a kit from VPW last fall, after the truck had been brought out of a 10yr hibernation. Steel needle, brass seat, appears to be a leather pump. I did have to drill a hole in the vertical portion of the vacuum passage of the top plate, to drive out the acc pump piston. I tapped the hole and installed a small set screw with sealer. I lightly sanded the bore for smooth movement in the top plate as well as the actual pump bore in the main body. The truck had been properly prepped for storage with the fuel drained from the tank and carb when it was put up, so it was not a nightmare to clean and prep for the new kit. After initial fire up, I discovered the mech fuel pump was dumping fuel into the crankcase. Ordered a kit for it, and came to the realization that the procedure was above my pay grade. Those double arms for the vacuum and fuel diaphragms were too much for my fat fingers to put back together, so I ordered a rebuilt pump from Midwest. I also ordered a tune up kit from them. Mistake on both. The pump leaked, and the spring arm on the points was mfd out of copper or some similar material that easily bent. Back to VPW for their tune up kit with plug wires and a new coil. I added a 12v fuel pump (the truck has a separate 12v system on it for civilian lights) and regulator. I set the regulator to 4psi.
The truck ran great, no issues whatsoever. Choke all the way in when hot, started easily, ran predictably, even won peoples choice award at a local Mopar car show.
About a month later it stalled while driving and was obviously flooded.
I have checked the 24v feed wire from the fender thru the dist housing to coil for shorts/grounding, have rechecked the points way too many times and always set to .020" I also went down to .017" to see if it helped low speed operation, but put them back at .020" due to no change. It's very apparent that it is over fueling. Even at about 2000rpm it loads up bad enough to have singular exhaust backfires about every 20 seconds. I'm guessing it's due to excessive fuel making its way into the exhaust and puddling, then firing off. This is why I have looked at possible ignition issues, but it all points back to the fuel.
I ran the electric pump with the top off the carb to verify that the fuel pressure was not pushing past the needle and seat, and to verify fuel level in the bowl. No seat leakage and the level looked ok. Not sure what the actual liquid level measurement is, but its lower than the 5/32" of the float top. The floats do not sink, or touch the edges of the bowl. I did not try the hot water method, but will do so.
What is weird, is that the truck starts fine when cold. A inch or so of choke, a little throttle upon engine coming to life and reduce choke fairly quickly. I'm in TX so its about 50F to 70f in the mornings now. Runs smooth and feels perky to throttle response for about 20-30 seconds, then starts flooding. I can keep it running for about another minute, but its loaded up, backfiring, so I shut it down to be easy on the old thing.
I've checked the proper ball size and location, spring placement and metering rod movements countless times. I've never gone into the governor of the carb. Anything in there I should worry about?
The fuel is local pump gas premium with ethanol treatment. I have drained the fuel and filled it with current fresh fuel.
I don't believe fuel should be running out the pcv nipple when I pull off the cap after it runs for a minute (engine off).
I will install a fuel pressure gauge and verify the regulator, just so it is known.
Thanks for the help

 

[o1951]

About a month later it stalled while driving and was obviously flooded.

It's very apparent that it is over fueling. Even at about 2000rpm it loads up bad enough to have singular exhaust backfires about every 20 seconds. I'm guessing it's due to excessive fuel making its way into the exhaust and puddling, then firing off.

I ran the electric pump with the top off the carb to verify that the fuel pressure was not pushing past the needle and seat, and to verify fuel level in the bowl. No seat leakage and the level looked ok. Not sure what the actual liquid level measurement is, but its lower than the 5/32" of the float top. The floats do not sink, or touch the edges of the bowl. I did not try the hot water method, but will do so.
What is weird, is that the truck starts fine when cold. A inch or so of choke, a little throttle upon engine coming to life and reduce choke fairly quickly. I'm in TX so its about 50F to 70f in the mornings now. Runs smooth and feels perky to throttle response for about 20-30 seconds, then starts flooding. I can keep it running for about another minute, but its loaded up, backfiring, so I shut it down to be easy on the old thing.
I've checked the proper ball size and location, spring placement and metering rod movements countless times. I've never gone into the governor of the carb. Anything in there I should worry about?
The fuel is local pump gas premium with ethanol treatment. I have drained the fuel and filled it with current fresh fuel.
I don't believe fuel should be running out the pcv nipple when I pull off the cap after it runs for a minute (engine off).
I will install a fuel pressure gauge and verify the regulator, just so it is known.
Thanks for the help

I agree, symptoms point to an overly rich mixture. Ethanol gas is a solvent, and dissolves old gums and crud in the tank and fuel system. It is possible some junk got into pressure regulator and it does not work right. I would not take it apart unless it is known bad. Install the pressure gauge as I recommended and lets see.

NO, gas should not come out PCV nipple.

I will throw something out that might help. On Rochester Quadra jet carbs sometimes the check ball or seat at the bottom of the accelerator pump bore would get messed up and not seal. When that happened, gas would flood into carb from accelerator pump jets. The other thing that happened was factory rebuild kits ( we tried to use OEM parts) often came with an elastomer instead of the leather on the accel pump plunger. If the bore was worn, it would not seal and the carb would flood from gas coming out the accelerator pump jets. If someone looks down carb throat while running, they should be able to see igf gas is coming out accelerator pump jets when it should not be. --- Wear safety goggles and proper protection just in case it backfires thru the carb. That blue flame is HOT.

I did a lot of rebuilds of Rochester, Holly, Carter carbs, but this was long ago. GM, Chrysler and Ford pretty much eliminated carburetors on civilian vehicles in the 1980's.

 

[Roger Friedrich]

I still think there is a compression problem or the valves are out of adjustment. The fuel could be at the base of the carb when he pumps the throttle. My engine needed to be started on ether also and when I torn it down to over haul it I found gas setting in the intake manifold

I talked to several old school mechanics in my area and the first thing they ask is what is the compression

 

[gerrykan]

.....I have checked the 24v feed wire from the fender thru the dist housing to coil for shorts/grounding, have rechecked the points way too many times and always set to .020" I also went down to .017" to see if it helped low speed operation, but put them back at .020" due to no change. It's very apparent that it is over fueling. Even at about 2000rpm it loads up bad enough to have singular exhaust backfires about every 20 seconds.

......What is weird, is that the truck starts fine when cold. A inch or so of choke, a little throttle upon engine coming to life and reduce choke fairly quickly.

......Runs smooth and feels perky to throttle response for about 20-30 seconds.................I can keep it running for about another minute, but its loaded up, backfiring, so I shut it down to be easy on the old thing.

I'm no SAE mechanic, and I didn't go back and reread the entire thread, but the backfiring sounds like it could be a bad Condenser in the distributor.
Breaker type ignition components available these days are often junk right out of the box. An entire batch from the same manufacturer could be bad.
Most (if not all) of these parts are made in China, or some other Country as cheaply as possible to maximize profits.

Also, have you examined the spark plugs after an incident?
Severe flooding should leave the electrodes wet, and smelling of gasoline.