Johnson FD-12 Won’t Run

[bobw]

The spark seems pretty weak on both cylinders, so I plan on installing new coils.   The motor didn’t run more than 10 minutes in the test barrel – the top cylinder looks like it didn’t fire very much, but I’ve never had a new plug get fouled so badly and so quickly as the bottom cylinder shows.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[fleetwin]

bobw wrote:

With the original air pulse pump fed from the air nipple on the manifold, I had removed the reed plate check valves and plugged one of the two ports to get pressure and vacuum off one cylinder (I’ve used this approach on several other motors when I used an air pulse pump).  See pic of reed plate plug.

 

In the 2nd test run with the new pump fed from the bypass cover, I left the reed plate plug in place and capped off the air nipple on the manifold.   Not sure if it will make a difference, but today I pulled the manifold and reed plate and re-installed the check valves on the reed plate.   In pulling the manifold and reed plate off, I also opened up the carburetor again just to make sure nothing was amiss there – it all seems OK.

OK, so you only plugged up one of those ports?  I “think” that should work fine provided the pressure nipple is capped off.  The only other thing to question/check is that the two different intake manifold gaskets are installed properly.

[fleetwin]

billw wrote:

To me, if I looked at those two plugs, I would be thinking I had poor spark on the one that is NOT fouled, as it doesn’t even look like it fired much at all. If you don’t have true, open-air spark testers, you can just rip the ground electrodes off regular plugs, creating a bigger gap. A good OMC ignition will jump that gap in open air.

I agree, this is often true.  Many times it is the clean plug that isn’t firing.

[bobw]

fleetwin wrote:

bobw wrote:

With the original air pulse pump fed from the air nipple on the manifold, I had removed the reed plate check valves and plugged one of the two ports to get pressure and vacuum off one cylinder (I’ve used this approach on several other motors when I used an air pulse pump).  See pic of reed plate plug.

 

In the 2nd test run with the new pump fed from the bypass cover, I left the reed plate plug in place and capped off the air nipple on the manifold.   Not sure if it will make a difference, but today I pulled the manifold and reed plate and re-installed the check valves on the reed plate.   In pulling the manifold and reed plate off, I also opened up the carburetor again just to make sure nothing was amiss there – it all seems OK.

OK, so you only plugged up one of those ports?  I “think” that should work fine provided the pressure nipple is capped off.  The only other thing to question/check is that the two different intake manifold gaskets are installed properly.

Yes, I had plugged off only one of the reed plate ports (see the pic included in my previous post).   The manifold air port is now capped off since I’m using the fuel pump installed on the bypass cover.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[The Boat House]

Possible leak (spark jumping to ground) in the ignition?
Occurs when voltage increases as you speed up the
motor but not at idle?
Tubs

[bobw]

The Boat House wrote:

Possible leak (spark jumping to ground) in the ignition?
Occurs when voltage increases as you speed up the
motor but not at idle?
Tubs

A possibility I suppose.   I installed new plug wires, plug terminals and boots but I’ll check for possible grounding at the armature plate when I install the new coils.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[The Boat House]

My experience comes from starting a motor
for the first time after a rebuild. After checking,
and rechecking, everything I’d hook up the coil
tester to test the coil I know is good and a
leak would reveal itself . Happened twice. Now
its a standard test for me after assembling a
magneto. Its easy to eliminate this as a possibility
with a coil tester like a Merc O Tronic. Without
one, if this should be you issue, it could be very
difficult to find.
Tubs

[bobw]

I wish I had a Merc O Tronic but I can only use my VOM to test the coil resistance.    The old coils measured 0.4 on the primary and 6300 on the secondary so theoretically they should be OK.    I’ve never had an ignition related problem after a total rebuild but then again, this is my first rebuild where I re-used the old coils.    I’ll just put in new coils and see what happens.  In the overall scheme of the cost of this project, a pair of new coils is nothing.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[bobw]

OK, after replacing the defective fuel pump and installing new OMC/BRP coils, I’m declaring victory.   Seems to run good now.   You’ll notice in the video that after tweaking the carb adjustments, the low speed needle knob needs to be moved to point downward toward the scale and at the very end of the video, the high speed needle was a little loose and opening richer and just needed the packing nut tightened up a bit.   Final carb adjustments will be done once it gets on a boat.

https://www.youtube.com/watch?v=FTsDbD03vHg

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[crosbyman]

real nice restoration… another oldy lives   🙂  thanks for the feedback

Joining AOMCI has priviledges 🙂

[Author]

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