M37 Not Starting-Troubleshooting help needed

rickv100 · Post by **rickv100** » Sat Jun 13, 2009 3:46 pm

I was pulling my M37 out of storage today. I was able to get the truck started after charging the batteries, filling the gas tank and carb bowl and it started on the first try.

I took the truck for a lap around the storage facility and parked it for the rollback to take it to the house.

When I went to restart it, I had a short occur due to a unconnected wire and now I can not get the truck to start.

I checked the fuel and I have gas in the carb. I pulled the wire on spark plug number 1 and tried to see if I could get a spark to jump when holding about 1/4" away from the block as the manual directed.

I pulled the cover on the distributor and the points are not stuck shut and I see no damage to the rotor button or the inside of the cap.

I also pulled wire 12 (lead to the distributor) and checked voltage with a voltmeter and have 24 volts at the wire.

Where should I check next?

Thanks,

Rick

powerwagontim · Post by **powerwagontim** » Sat Jun 13, 2009 4:20 pm

Rick,
You mention trying to get a spark to jump from your plug wire, but you didnt say if you got one. I presume you didnt. Also what was the wire that shorted?
Tim

rickv100 · Post by **rickv100** » Sun Jun 14, 2009 10:45 am

Tim,

Yes, I got no spark.

The horn wire was unattached and was grounding to the engine block.

Rick

DJ · Post by DJ » Sun Jun 14, 2009 3:38 pm

You have power to distributor,check for power to coil and points,then manually open and close points(carefuly) to check for a spark.

m15256 · Post by **m15256** » Sun Jun 14, 2009 6:50 pm

I had one of the point contacts fall off the arm once. The center contact fell off a rotor once. Stared at both of those for a long time before it dawned on me they weren't there. If the points spark on opening, you should get a spark at the plug. If your plug wires aren't junk. Maybe the points slipped and aren't opening or closing. Little wire to the coil got crimped at some point and finally broke? Usually it's something really basic and really simple. You just have to do each little step along the ignition path until the missing element stares you in the face. I traced one down at night illegally parked on an airport access road with a six year old with me. (at least it wasn't raining.)

rickv100 · Post by **rickv100** » Sun Jul 05, 2009 1:54 pm

I am still having problems getting my truck started.

I replaced the points and the condensor, and checked the coil. When the engine turns over, I can get a spark jumping between the wire and the body of the spark plug.

I checked the carberator and I have fuel going into the intake manifold.

I defintley have air to the intake as I remove the air cleaner.

I pulled spark plug #1 and if I ground it out against the block I do not see a spark.

Would it be possible to not have a strong enough current to fire the spark plugs but the get a spark to jump the gap at the wires?

I have the military style spark plugs installed in the truck.

Thanks,

Rick

Lifer · Post by **Lifer** » Sun Jul 05, 2009 7:19 pm

rickv100 wrote:Would it be possible to not have a strong enough current to fire the spark plugs but the get a spark to jump the gap at the wires?

I have the military style spark plugs installed in the truck.

Yes, it would be possible. If you had a fat blue spark when grounding the wire to the block but no spark at the plug, it's very likely that the plug may be bad. Cleaning/gapping the plugs may help. Replacing them wouild be even better.

If you had a weak yellow spark when grounding the wire to the block and the batteries were fully charged, it's probably a points/condenser issue, but you said you replaced those.

Hang in there. You'll track it down sooner or later.

m37jarhead · Post by **m37jarhead** » Mon Jul 06, 2009 5:02 am

I'm no expert here but your last post said you have spark from the wire
to ground but not through the spark plug. Hmmmmm. Bad plug(s) maybe?
Bad wire(s)? I'd check the plugs and the wires with a multi-meter to check
for resistance. They should all be approximately the same, if not, you
can at least weed out the bad ones.

Checked compression?
Checked timing?
1-5-3-6-2-4 (not likely you changed anything there but worth checking)

If you've checked everything that you know (twice) try pull starting it
down the road..... maybe with a shot of either. Sometimes these old
vehicles just get grumpy and resist battery starting after storage because of old gas, sticking valve(s), ad infinitum.
I always say these old vehicles "are just Briggs and Stratton technology"
but when they're hard to start it will sure drive you nuts.
m37jarhead

Nickathome · Post by **Nickathome** » Mon Jul 06, 2009 8:24 am

How are your batteries? I am also no expert but if your batteries are low you will be able to crank the engine and should get a weak spark, but it won't be enough to fire the engine.

I have a funny feeling your coil is bad. I seem to remember my truck doing what you describe(I did not have a short though) and after replacing the coil the engine fired right up. Worth a shot.

rickv100 · Post by **rickv100** » Mon Jul 06, 2009 2:23 pm

Thanks for the assistance. I will work through your suggestions and let you know what I find.

Thanks,

Rick

rickv100 · Post by **rickv100** » Fri Jul 10, 2009 4:10 pm

Continuing on my saga with my truck.

I replaced the batteries with two new ones today as I was getting a dull yellow spark and my meter was showing the batteries in the red. A test at the battery supplier showed they needed replacing.

I replaced the batteries and I get a reading in the mid yellow range on my meter on the dash, spark is a healthy blue spark of #1 wire.

I still can not seem to get it to start.

From trying to start the truck I accumlated about an 1/8 of fuel in the intake manifold. I pulled the carb and removed the excess fuel.

When I tried to start it again I got a few coughs but nothing since.

As a check I removed the distributor top and set the engine at Top Dead Center. The rotor was at 7 o'clock position which would be correct for spark plug #1.

So I reassembled the distributor and still no luck.

So to recap I have the following symptoms.

1. I have spark from wires to ground. Fresh Batteries
2. I have fuel. Fuel pump is working correctly.
3. I have air to intake.

When I pulled spark plug #1 I noticed that the plug was not wet like if it was flooded.

I am working with the troubleshooting list in the TM but I am stumped at this point.

Rick

MSeriesRebuild · Post by **MSeriesRebuild** » Fri Jul 10, 2009 11:32 pm

rickv100 wrote:Continuing on my saga with my truck.

I replaced the batteries with two new ones today as I was getting a dull yellow spark and my meter was showing the batteries in the red. A test at the battery supplier showed they needed replacing.

I replaced the batteries and I get a reading in the mid yellow range on my meter on the dash, spark is a healthy blue spark of #1 wire.

I still can not seem to get it to start.

From trying to start the truck I accumlated about an 1/8 of fuel in the intake manifold. I pulled the carb and removed the excess fuel.

When I tried to start it again I got a few coughs but nothing since.

As a check I removed the distributor top and set the engine at Top Dead Center. The rotor was at 7 o'clock position which would be correct for spark plug #1.

So I reassembled the distributor and still no luck.

So to recap I have the following symptoms.

1. I have spark from wires to ground. Fresh Batteries
2. I have fuel. Fuel pump is working correctly.
3. I have air to intake.

When I pulled spark plug #1 I noticed that the plug was not wet like if it was flooded.

I am working with the troubleshooting list in the TM but I am stumped at this point.

Rick

Sounds like by your description that you have the correct ingredients for fire off, but something isn't right obviously. My next step would be as I've said many times before, do a compression test. Simple, quick, will tell you right away what you need to do next in the process of elimination. Post the test results & we'll help you from there.

Post by **Cal_Gary** » Mon Jul 13, 2009 5:49 am

I agree a compression test would tell you a lot, but I would also look at the plug wire arrangement on the distributor-are you set up for clockwise rotation or counter-clockwise? If it is backward, it won't run but will fire on #1 plug like everything is in ok.
Gary

rickv100 · Post by **rickv100** » Mon Jul 13, 2009 7:36 am

Cal,

I can reverify with the manual but truck was running. I expereinced a short and since then have not been able to get the truck restarted.

I will check the compression on the truck but I keep leaning to the issue being in the distributor. I have replaced the condensor and points.

I have spark with a spark plug wire held approx 1/4" above the block.

Rick

MSeriesRebuild · Post by **MSeriesRebuild** » Mon Jul 13, 2009 8:14 am

rickv100 wrote:Cal,

I can reverify with the manual but truck was running. I expereinced a short and since then have not been able to get the truck restarted.

I will check the compression on the truck but I keep leaning to the issue being in the distributor. I have replaced the condensor and points.

I have spark with a spark plug wire held approx 1/4" above the block.

Rick

If you have a spark jumping to ground on the block, the issue isn't likely the distributor. If a distributor problem exist, you would have no spark.

M37 Not Starting-Troubleshooting help needed

M37 Not Starting-Troubleshooting help needed

A bit more information please

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