Johnson FD-12 Won’t Run

[Bob Wight]

Finished the restoration on my Johnson FD-12 and the first barrel test run didn’t go so well.   Motor starts up OK and runs good for 5 to 10 seconds then just speeds up on its own and dies.   Didn’t want to restart unless I squeezed the primer bulb again and applied full choke.   I converted this to single line fuel supply with a fuel pump and the running symptoms seem to point to fuel starvation so I’m thinking the pump is not working right.   Some other factoids – compression is 110 in both cylinders, has new piston rings, I re-used the old coils which tested good and seem to throw a good hot spark.  Cleaned and re-used the old OMC points.  Overhauled the carburetor including the idle circuit.  Started with carb low speed 1-1/2 turns open and high speed 1/2 turn open.

I’m open to any suggestions for things I can check.   Here’s a short youtube video.   It ran like this about 5 different times before I gave up.

https://www.youtube.com/watch?v=3gtR2VC3EOY

 

 

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
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]

first thing to do is check for fuel at the pump output… the engine runs  but starves and  so fuel is obviously  in shortage.

tried openning the  idle needle a bit more ??

Assuming the carb is all cleaned up  and tested for  air flow upside  down and right side up  to check the needle  operation ….

did you do  the  side cover mod to get a pulse  or the air pulse nipple  mod behing the carb ??

Engine   pulse to run the pump may be missing or inadequate for some reason

what pump was used   mikumi,, OMC type    square,  or john deere round pump ??  post a  pump picture  if possible

 

believe it or not I once installed a square pump on a side cover but failed to properly line up the  rear pulse hole !!! 🙁  behind the gasket

 

 

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[Finn Freeman]

I agree that it seems like the pump isn’t working properly. Towards the end of the video, it sounded how it would sound if you were leaning the mixture screw out too much, and it seemed like it sneezed a couple of times. Do you have anyway to test the pump off of the engine?

[fleetwin]

OK, sure sounds like it is running out of fuel.  Did you “cap off” the pressure port on the intake manifold completely.  The engine will sneeze and fart if that port is leaking.  Will the engine continue to run if you pump the fuel bulb?  If so, fuel delivery issue is indicated.  Perhaps the new fuel pump in NG, how did you rig it up?  Did you get a new bypass cover with a fuel pump port, or do it some other way?  Using OMC pump, or aftermarket?

The pump may be NG, but you sure want to check other stuff first.  That fuel filter on the port side of the engine may be plugged up, or perhaps there is an air leak on the inlet side of the fuel system.  Have you tried the tank on a different engine?

[Bob Wight]

crosbyman wrote:

first thing to do is check for fuel at the pump output… the engine runs  but starves and  so fuel is obviously  in shortage.

tried openning the  idle needle a bit more ??

Assuming the carb is all cleaned up  and tested for  air flow upside  down and right side up  to check the needle  operation ….

did you do  the  side cover mod to get a pulse  or the air pulse nipple  mod behing the carb ??

Engine   pulse to run the pump may be missing or inadequate for some reason

what pump was used   mikumi,, OMC type    square,  or john deere round pump ??  post a  pump picture  if possible

 

believe it or not I once installed a square pump on a side cover but failed to properly line up the  rear pulse hole !!! 🙁  behind the gasket

 

 

I did try opening the carb needle a little more but it didn’t seem to make much difference.   After the carb overhaul and prior to installation, I did test the carb for float/needle seating upside down and rightside up – needle was seating correctly.   I did the air pulse nipple mod to get my air source for the pump, which I’ve done on several motors with no problem.  The fuel pump is for a Kohler or B&S engine lawn tractor with advertised flow rate of 4 liters/hr. but for the price I suspect it’s a Chinese made product.   Thought I might swap it out to a Mikuni pump.   I’ll try to include a picture of the pump but don’t know if will load.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
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."

[Buccaneer]

Gotta wonder if the Chinese use the same crap they sell us.
I used a B&S fuel pump once on one project, which seem to
work okay, but I can’t remember the part number. No
doubt it’s made in China as well.

Hang in there, no doubt it will be a Swiss Watch soon!

Prepare to be boarded!

[Bob Wight]

fleetwin wrote:

OK, sure sounds like it is running out of fuel.  Did you “cap off” the pressure port on the intake manifold completely.  The engine will sneeze and fart if that port is leaking.  Will the engine continue to run if you pump the fuel bulb?  If so, fuel delivery issue is indicated.  Perhaps the new fuel pump in NG, how did you rig it up?  Did you get a new bypass cover with a fuel pump port, or do it some other way?  Using OMC pump, or aftermarket?

The pump may be NG, but you sure want to check other stuff first.  That fuel filter on the port side of the engine may be plugged up, or perhaps there is an air leak on the inlet side of the fuel system.  Have you tried the tank on a different engine?

I plugged off one side of the intake behind the reed plate and ran an air pulse line from the manifold to the pump.  Main incoming fuel feed to fuel filter inlet, fuel filter outlet to pump inlet, pump outlet to carburetor.   During the last run when it started to die out, I did squeeze the tank primer bulb and it got to running again, so I’m pretty sure the Chinese made pump is NFG (it’s a Mikuni look-alike knock-off product).   By the time I quit fooling with it, I was getting low on fuel in the tank, so I plan on getting some fresh gas tomorrow and I’ll check the fuel pump output.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
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."

[Steve Martin]

Is the gas tank vented?

[Bob Wight]

Steve – yes, the tank is vented and open.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
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]

I had exchanges  some time ago about these pumps with the gold mesh  similar to your  B&S pumps.   AlthoughI had no problems it seems these gold mesh pumps are more  for  4 stroke engines  more than 2 strokes…..

the pulse line  should normally push air but could in theory push oily vapours enough to degrade the pulse pressure to the pump .

try another pump style (square mikuni)  maybe  just for the fun of it  or….drill and tap a  side cover  to mount a nipple  to pulse the pump and… plug off the  pulse nipple behind the carb

keep at it ….patience brings joy

 

 

Joining AOMCI has priviledges 🙂

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