Ignition Problems...

[pwrwagonfire]

Well, changed my points and condenser today. Truck STILL will not run, getting closer to the end of my rope!

So...whats next gentlemen?

[RMS]

hmm a gas motor only needs a few things to make it run fuel, spark and compression but every thing has to happen at the right time.

I have the manual for the M-37, but I don't have a military distributor

I must note that the civilian oil pump has a centered slot and the dizzy has a centered tang. with the civilian setup it is possible to install the dizzy 180 out. where as the military dizzy will only fit in one way with its offset tang and slot.

so if you truck has backfired out the carb even a little your probably 180 out.

[pwrwagonfire]

I can pour gas/quick start down the carb, and it STILL won't fire...

[majorhitt]

I didn't read all the post. Did you check for voltage to the distr.? Then check the coil. Check for a good ohm reading from dist to the frame. 0.02 Ohms Do you have no spark what so ever? Took a plug out and saw a spark to the eng block?

[pwrwagonfire]

I didn't read all the post. Did you check for voltage to the distr.? Then check the coil. Check for a good ohm reading from dist to the frame. 0.02 Ohms Do you have no spark what so ever? Took a plug out and saw a spark to the eng block?

I am getting power to the distributor, just not firing...I replaced the coil, and confirmed I am getting voltage to the coil, I put a plug on the engine block and got a weak spark, so today I replaced the points and condenser...so far I have new cap, rotor, points, condenser, and spark plugs...I have also rewired and cleaned up/checked the wiring in the ignition system and can confirm that it is indeed wired correctly

My engine was gutted and re-built last summer, so I'm ASSUMING that compression is not the issue.

Would be perhaps the IBR?

Possible stupid question: would a split exhaust manifold affect the compression enough to cause thee problems for me??

[majorhitt]

Well It sounds the same as mine now. I tried all the items you mentioned. Weak spark or that what it looked like. After several friends helping and no progress, A friend of a friend came over and we put it on a roll back. At his garage he checked every thing,even a small scope down the plug hole to check the valve position (open or closed), still not firing. His garage had a very long down hill drive way, He said every thing indicates that this should be able to run. Then he said lets push it down the driveway and see if it will start. I said you're close enough to the river let's just push it in the river( at this point I was so frustrated that sounded like a good idea) Any way we pulled it out of the garage got the tow vehicle out of the way gave it a push with another and less than twenty feet it was running. Now for the fun part, It had no brakes and I was going down hill. Well anyway from that point on it starts like it should. The motor was just a little too tight after the rebuild. Not enough push to keep the motor turning. At times It would sound like it wanted to but didn't. Now it turns over easy and runs good. hope this helps.

[DJ]

Sounds like you got gas and spark. Now you need to make sure they are at the right spot at the right time. Get #1piston at TDC then check the rotor to see if it is at the #1 position on the cap. Would also check compression,dumping gas down the carb could have washed tthe cylinder walls clean. How old is the gas ?

[pwrwagonfire]

Gas was new (a month ago) when I started working on this problem...I have added sea foam to stabilize the fuel, and get rid of any condensation which may be present

Just in the middle of 10-14" of snow...which messes up my plans to fix the m-37 this week!

[pwrwagonfire]

Well It sounds the same as mine now. I tried all the items you mentioned. Weak spark or that what it looked like. After several friends helping and no progress, A friend of a friend came over and we put it on a roll back. At his garage he checked every thing,even a small scope down the plug hole to check the valve position (open or closed), still not firing. His garage had a very long down hill drive way, He said every thing indicates that this should be able to run. Then he said lets push it down the driveway and see if it will start. I said you're close enough to the river let's just push it in the river( at this point I was so frustrated that sounded like a good idea) Any way we pulled it out of the garage got the tow vehicle out of the way gave it a push with another and less than twenty feet it was running. Now for the fun part, It had no brakes and I was going down hill. Well anyway from that point on it starts like it should. The motor was just a little too tight after the rebuild. Not enough push to keep the motor turning. At times It would sound like it wanted to but didn't. Now it turns over easy and runs good. hope this helps.

Good to know theres light at the end of the tunnel!

[w30bob]

Hi pwrwagonfire,

A cracked exhaust manifold won't affect compression or the engine's ability to start. Sorry for coming to this party late.....but how about a little recap?

The truck did run when parked last, right? Or was it not run since the engine was rebuilt?
If it was run after it was rebuilt.....how long did it sit between the last time it ran and now?
You poured gas down the intake, but is the carb spraying fuel like it's supposed to?
The choke is working, right?
It is timed right now, right?
What did you do to the truck, if anything, between now and the last time it ran?

regards,
bob

[pwrwagonfire]

Hi pwrwagonfire,

A cracked exhaust manifold won't affect compression or the engine's ability to start. Sorry for coming to this party late.....but how about a little recap?

The truck did run when parked last, right? Or was it not run since the engine was rebuilt?
If it was run after it was rebuilt.....how long did it sit between the last time it ran and now?
You poured gas down the intake, but is the carb spraying fuel like it's supposed to?
The choke is working, right?
It is timed right now, right?
What did you do to the truck, if anything, between now and the last time it ran?

regards,
bob

Better late than never! Thanks for jumping in! I'm really hoping all the knowledge on this forum can help me solve the issue.

The truck's engine was rebuilt, and the carb gone through and given an "OK" by a really good carb guy last summer, when I picked it up from the shop, the timing was fine. It ran very well for a few months, I tried to run it for 30 minutes or so every few days after work (unfortunately not registered for the road yet). Then, the fuel pump quit in November, I replaced it and added an inline filer, and it once again ran with no issues until just after Christmas 2012. Went outside to start it, and it wouldn't crank over.

I first checked out the fuel system once again, bleeding it all the way to the carb, confirming the fuel pump is functioning correctly, and replaced the inline filter. I have had an issue simular to this with a WM300 at work, and it turned out the be the needle valve right before the carb, so I cleaned that up really good. I tried gas and starting fluid in the carb to see if it ran (I was still wondering if there was a fuel delivery issue at that point), but still wouldn't fire.
At this point I began to look at the ignition system. I changed the coil, cleaned up some messy wiring, and confirm the coil was getting power. Then I installed new plugs (gaped correctly), new points (adjusted to matchbook cover for now), a new condenser, new rotor, and new cap. Still not turning over. The only things left I could replaced as far as I can see is the IBR, and the plug wires.

When I crank it over several times, you can SMELL the fuel, and I end up flooding the carb...I have not checked the choke cable, that will be the next thing I visually check tomorrow when this snow stops!

Any help is appreciated

[RMS]

an over fueled flat head will not start. gas likes to pool in the manifold and a wet plug wont go bang!

back when my 37 was new to me I often forgot to push in the choke and hand throttle once it was hot. then i would shut it down and hours would be spent (usually at a gas station) trying to get her to fire. what I would end up doing was remove the plugs and hit them with a flame and burn off the raw gas. unknown to me back then was during the time it took to clean the plugs the gas in the manifold and CC would evaporate. allowing nicely atomized gas to enter the CC rather than a big splash from the manifold.

the m37 is set up beautifully for a one man tune up. from the driver fender you should be able to control the timing throttle and starter. make sure the hand throttle is all the way in, back the idle screw all the way out, mixture screw should be around 2.5 turns out from the stop. set the choke to 3/4 open to increase the venturi effect, loosen the dizzy just a bit so you can turn it but not so much that it will flop around. pull the plugs and hit them with a torch get them hot and install. with a timing light set up to verify spark crank the motor over by pulling on the starter with a free hand. after a few cranks and no bang sniff the tailpipe if you smell raw gas go back to the carb. if you do not smell gas crank and quickly burp the choke (may only work on stock carb) the vacuum created should suck gas out of the bowl but with the throttle plate closed no allow much to enter the manifold or CC. then re crank and open the throttle plate a bit to allow the gas into the CC it should go bang if not move the dizzy a touch and repeat. start by pulling the plugs if their wet go back to the carb. if dry turn the throttle screw in 1/4 turn and repeat the process.

when this snow stops!

if it is below freezing even a good running flatty is tricky to start. I feel the need to mention that the flathead will not run on ether alone no matter how much you spray.

[m37jarhead]

New engine? Not run for a while? Valve or valves stuck open?
I'd take a compression test on each cylinder.
I'd also pull the M37 with a chain or strap.....get that engine spinning at higher
rpm than you can with a starter...... worked on my GPW and
it ran perfect after that. Had weak spark and engine was not run in months/years.
Still don't know why it would not hit right off after sitting. Pulling it worked.
Jerry

[pwrwagonfire]

New engine? Not run for a while? Valve or valves stuck open?
I'd take a compression test on each cylinder.
I'd also pull the M37 with a chain or strap.....get that engine spinning at higher
rpm than you can with a starter...... worked on my GPW and
it ran perfect after that. Had weak spark and engine was not run in months/years.
Still don't know why it would not hit right off after sitting. Pulling it worked.
Jerry

Perhaps this should be what I try first, as its very simple

I'm going to try and tune my carb like the poster above you suggested as well, I KNOW for a fact that the idle is off a little

[m37jarhead]

Good.... try it. Always try the cheap and easy things first.
Do a compression test and if the numbers look good, pull the
old gal down the road. Might try shooting a little starter
fluid in at the same time.
Jerry