M37 Engine will not start

[jonathan.shields]

1. Comp 90psi all pistons
2. Plug wire ohm to 0 no resistance and no leakage to the jacket 3. Plugs appear serviceable set at 30 guess that is ok I cleaned them.
4. Internal dist cap had no cracks. The spring to rotor button ohmed out to 0. But when ohming from the spring side of the cap to the rotor side all 6 ohmed at 4.5 resistance. Is that ok?
5. Now the coil fron plus to minus post ohmed at 6.7 and the center to either post was 9.95 bad right? So I installed an export coil reading 7 post to post and 15 to the center I confirmed 24 volts were getting into the coil.
6. Did not check the points. Closed it up and it would not start
7. New Carburator and fuel is getting to the carb electrical pump pushes the fuel steadily. Filters are clean.

 

[majorhitt]

The coil info you need is across the primary terminals you should have 6 ohms, on the secondary to either primary terminal 15.5-- 15k ohms. you didn't say if you had spark at the plugs. I had an issue like yours where everything was where it should be but would not start. A little push down a hill and pop the clutch, fried up. Rebuilt motor a little tight, the push did it for me.

 

[poppop]

Sounds like you are not getting fire. Pull the cap and stick a screwdriver on the points and ground it. If you get sparks then fire is getting to the points. Roll the engine and look for a spark between the points. If none then sand the points and try again. If its sat for a long time the points are probably corroded. Mine only ran on three cylinders when I got it. The cap looked OK but was not. When I replaced it then it ran fine.

 

[Roller]

As stated above, check to see if there is spark to the plugs. Pull a sparkplug and ground it to the block and check for spark.

Frank

 

[jonathan.shields]

Here is an update I am getting 24 volts on the primary terminals and the secondary when the points are closed I do not get any ...well maybe just a little current through the secondary. I will check for spart at the plug tonight. I am going to set up a camera and record the plugs firing. Also changed out the points and condenser and three plugs The internal dist cap looks fine but as I stated earlier there is a resistance of about 4+ ohms when I test the 6 contacts rotor side to plug wire side. Is that OK? The engine cranked after a long bout with it hitting and missing.....a little starter fluid then it after it fighting to start it cranked and ran better than before. No backfiring. I fan it for 5 minutes then let it idel when it it stopped.....Idle set to low I believe. The motor would not crank there after? Just a reminder I have a new carb, coil, points and condincer/capacater 3 plugs. Wires seemed to be fine. I will look at the color of the spark tonight. Any other suggestions would be greatly appreciated.

 

[glcaines]

Why only replace 3 of the plugs?

 

[Tuko]

Why only replace 3 of the plugs?

50% chance of replacing the bad one

 

[jonathan.shields]

Replace all plugs and the old ones were good as well

I will use my jeep to check the plug wires tonight. I replaced all my new jeep plugs with those I took off the the m37 and all are fine

 

[jonathan.shields]

Only thing I was able to do was apply direct power to the distributor via the starter. I wanted to bypass the ignition switch to ensure there was not a problem in it. NO LUCK still dead in the water.

 

[glcaines]

Why do you think the problem is ignition and not fuel? In post #5 you mentioned that the engine ran for 5 minutes and then died when it was idling. This means that you had spark at that time. I would suspect a fuel problem at this point, but I would first eliminate some potential ignition problems.
1. Check the spark. It doesn't sound like you have adequately checked for good spark. Forget the camera, pull one of the plug wires off the plug and connect it to another uninstalled plug. Ground the plug and have someone turn the engine over and make sure the spark is strong and blue.
2. Make sure the proper wires go to the plugs. I've seen many engines with the plug wires mixed up.
3. Assuming you have good spark, check the ignition timing. You can't do a perfect test without the engine running, but you can hook up a strobe light and crank the engine over to see if the points are opening at approximately the correct time. I suspect this is not a problem since the engine ran 5 minutes once.
4. Assuming hot spark and adequate ignition timing, it is time to check the fuel system.
5. Is the fuel pump operating properly?
6. Is the fuel level in the bowl at the proper level?
7. Will the engine fire or start when a small amount of gas is put into the throat of the carb? How about ether?
8. If the engine will start and run for a few seconds or minutes it is time to look at the fuel pump and carburetor.

 

[EMD567]

Is the M37 24 volt or 12? The 24 volt system won't work on anything but a 24 volt system. If you used a 12 volt condensor on a 24 volt system, it won't run long, if at all.

 

[Stan]

I thought 90 psi on a compression test for this engine was a may or may not even run.

 

[Roller]

90 psi is the low limit, should run but needs overhaul.

Frank

 

[jonathan.shields]

Double check the points gap. I decided to see if #6 was in sync with the timing marks. I unscrewed the access plug over the piston, then place a 16 gague wire down into the hole. Rotated the motor until the wire reached the maximum height of the stroke. Looked at the rotor button to see if it was pointed in the direction of #6 or #1. It was in the direction of #1. I then viewed the timing marks on the pully wheel and made sure it was in the center. I then looked at the points and they were no where near open. Well, I then rotated the engine untill the points were open and noted the distance was about 1 inch past any of the timing marks. I have not attempted to adjust the distributor but I will tonight. Now did this jump time. Did the chain skip a link? If I adjust the distributor will the valves still be synced with the piston stroke?

 

[zak]

The TM's for the M-37 series of trucks are some of the best for military veh's. Their illustrations will clearly show how to set the timing.

 

[zout]

Some of the questions asked are basic engine concepts.
1. Air needed to fire it up
2. Compression needed to fire it up
3. Sufficient spark needed to fire it up
4. Of course FUEL needed to fire it up

If you have all of these above components - it should run - if it does not - you took the step to test timing to see if its where it belongs to fire.
Someone may have installed a new oil pup - distributor is run off the pump gear - to set dist - you have to have oil pump aligned.

I would tell you how to advance your ignition wires to see if it fires up like we use to do to ole gasser v8 engine - but this again is engine basics - look in the TM how to set the oil pump timing - with the firing order set to exactly where it needs to be - it does NOT get set off TDC.

 

[Roller]

Double check the points gap. I decided to see if #6 was in sync with the timing marks. I unscrewed the access plug over the piston, then place a 16 gague wire down into the hole. Rotated the motor until the wire reached the maximum height of the stroke. Looked at the rotor button to see if it was pointed in the direction of #6 or #1. It was in the direction of #1. I then viewed the timing marks on the pully wheel and made sure it was in the center. I then looked at the points and they were no where near open. Well, I then rotated the engine untill the points were open and noted the distance was about 1 inch past any of the timing marks. I have not attempted to adjust the distributor but I will tonight. Now did this jump time. Did the chain skip a link? If I adjust the distributor will the valves still be synced with the piston stroke?

Was number 6 on the compression stroke or the exhaust stroke?

Frank

 

[jonathan.shields]

WE are running!!!! Hop on! Used #6 TDC technique because timing marks are hard to see. Then adjusted distributor till points opened. Pulled started....bateries were weak. I allowed the engine to get to operating temperature before shutting it off. Then started it up using starter. It worked fine. Cranked again this morning! I will give it a long road test this weekend.

THANKS TO ALL........I keep reminding myself these were built by the lowest bidder, but you gota love them!

 

[greeno]

Sweet! I know the feeling.

 

[majorhitt]

I know the feeling also. After several weeks of not getting anywhere and being totally frustrated, the mechanic that I was working with said let's push it down the drive to see if it starts that way. I was so frustrated I said we'er by the river we might as well push it in there. Down the drive we went pop the clutch and it ran from there on. Glad you got it running. I was there.