Re: [MV] M-37 starting problems

Alan Bowes (inbox@todacosa.com)
Sun, 25 Apr 1999 22:42:21 -0600

Hi again, Brent,

As already mentioned, it sounds like you need to check the choke operation.
Also keep in mind that the accelerator pump in the M37 is vacuum operated,
so you can't "prime" the engine by pressing the gas pedal before starting.
Once the engine starts, the accelerator pump should work fine, unless the
old leather seal has shrunk or the ball check valves are stuck, etc.
However, if it runs OK after starting, with no hesitation when you step on
the gas after the engine has warmed up, then I'd say that it might just be
the choke. Some M37s were equipped with a manual priming system that used a
hand pump mounted in the dashboard. Lacking that, at cranking speed your
choke would have to be fully closed to develop sufficient vacuum in the carb
throat to draw enough fuel out of the carb bowl and through the nozzle.

Make sure the choke is closing all the way, and that the little
spring-loaded flap in the choke plate is working properly. Generally, unless
it's really cold, just apply full choke long enough to start the engine,
then back it off about halfway for a minute or so, then all the way off. If
you have a close look at the choke linkage, you'll see that when it's
properly adjusted and you apply full choke, the choke plate should be held
positively shut, with no spring action in the choke linkage itself (although
the small spring-loaded flap in the choke plate is designed to open when you
crank the engine with full choke applied). This little spring-loaded flap in
the choke plate limits the vacuum in the carb throat and prevents the engine
from flooding from sucking too much fuel out of the bowl when you crank it
with full choke applied.

Did you happen to check out my carb and governor overhaul articles at:

http://todacosa.com/html/m37-pw-service.htm

NOTE: The articles may take a couple of minutes to download, since each one
has somewhere between 15 and 20 pictures (plus the connection can get a bit
slow from time to time). You can click on the pictures for even larger
images.

Have fun,

Alan

Brent McClearen wrote:

> List,
> Got home from a cub scout campout today and decided to work on the M-37.
> It wont start without starting fluid. Runs great after that!
> I have installed the following: (all new)
> dist. cap
> coil
> rotor
> points (0.018)
> condenser
> distr. noise filter
> 1 new plug to replace incorrect plug
> gas is clean, fresh
> gas filter is new
> oil and filter done
> cleaned and gapped all plugs
>
> Any ideas from the field?
> Brent brent@multipro.com

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