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50 HP VRO to Mix Fuel pump

C

Cp02

New member
Good morning everyone,

I recently converted my 2003 Johnson 50 HP from the VRO to conventional fuel pump. I had no power on plane with the VRO and decided it was time to swap over to the conventional and change the plugs at the same time.

I purchased the SIERRA #438556, removed the pulse port bolt on he side of cylinder 1 plugged everything in and capped off the VRO pulse line. The engine has trouble starting and will not stay on.

Since everything ran fine 24 hours before I didn’t believe it was the carbs but looked them over anyways. The carbs are very clean, and there’s brand new spark plugs in the engine. Gas lines and primer bulb are also all brand new I swapped them out while changing the fuel pump.



I’ve looked over everything. The engine will start for about 10 seconds like a rabid animal and die out.

Has anyone else had this issue after converting?
 
Have to say it over and over.----Trouble shooting starts with a compression test.---Post the actual values here.-----And does spark jump a gap of 3/8" on both leads ?----Checked the flywheel key ?----Water in the fuel ?------Changed the impeller every 5 years ?-----Checked gear oil ?
 
Did you get your fuel hoses put on backwards by mistake?If I remember right the fuel in from the tank goes on the black plastic cap and fuel out to the carbs goes on the other hose barb.
 
racerone said:
Have to say it over and over.----Trouble shooting starts with a compression test.---Post the actual values here.-----And does spark jump a gap of 3/8" on both leads ?----Checked the flywheel key ?----Water in the fuel ?------Changed the impeller every 5 years ?-----Checked gear oil ?
Click to expand...
Everything on the engine is top notch. The lower unit was just serviced. Compression on both cylinders is 125. Spark jumps a 3/8 gap. Have not checked the flywheel key(not sure what that is) - the fuel is brand new.

The engine was idling and starting with no problems about an hour before on the VRO.
stork55 said:
Did you get your fuel hoses put on backwards by mistake?If I remember right the fuel in from the tank goes on the black plastic cap and fuel out to the carbs goes on the other hose barb.
Click to expand...
 
Cp02 said:
Everything on the engine is top notch. The lower unit was just serviced. Compression on both cylinders is 125. Spark jumps a 3/8 gap. Have not checked the flywheel key(not sure what that is) - the fuel is brand new.

The engine was idling and starting with no problems about an hour before on the VRO.
Click to expand...
stork55 said:
Did you get your fuel hoses put on backwards by mistake?If I remember right the fuel in from the tank goes on the black plastic cap and fuel out to the carbs goes on the other hose barb.
Click to expand...
The fuel lines are for sure on correctly.
 
So a new factory fuel pump mounted with a gasket should work like a charm.---Are both carburetors opening up all the way ?----Is timer base rotating to advance timing ?-------If flywheel key is sheared the timing will be way off.
 
racerone said:
So a new factory fuel pump mounted with a gasket should work like a charm.---Are both carburetors opening up all the way ?----Is timer base rotating to advance timing ?-------If flywheel key is sheared the timing will be way off.
Click to expand...

I would eliminate anything carburetor related. They are tuned correctly and everything is functioning the way it should. There is a deeper problem that I can’t find.

I haven’t looked into anything on timing. Timer base nor flywheel key. I will look this over later after work and get back.

Thank you for your quick response.
 
You said you replaced the fuel line and primer bulb,stupid question but is the arrow on the bulb pointing towards the engine.Was the fuel pump and hose quality parts or Amazon China junk?Try priming the engine then start it,when it dies remove the drain plugs on the float bowls and see if any fuel comes out.
 
racerone said:
Should be easy to diagnose this.----Well ----it would be on my workbench.
Click to expand...
I did some more reading on the timing and Fly wheel key before I go ahead and get the puller to remove the flywheel.

From what it looks like there is excess unburnt fuel dripping from the exhaust (from what I’ve read could be a sign of under combustion) due to timing inconsistencies.


I’m assuming this could also be from me trying to get the engine started for so long and there’s just gas getting flushed through the system and since it’s not starting it’s not burning any.

One more really important thing I forgot to add:

To get the engine to fire up on a cold start— first time working on it for the day —
1: click the priming solenoid
2: push throttle all the way down for a few seconds and then back to N
3: turn the key… Johnson fires up super hot for ~5 s
4: Johnson dies… with my hopes and dreams
 
stork55 said:
You said you replaced the fuel line and primer bulb,stupid question but is the arrow on the bulb pointing towards the engine.Was the fuel pump and hose quality parts or Amazon China junk?Try priming the engine then start it,when it dies remove the drain plugs on the float bowls and see if any fuel comes out.
Click to expand...
Arrow is pointing in the proper direction—- I will run your test tomorrow and get back to you.
 
Prime the bulb on the hose.----Advance throttle only lever.------Push key in while cranking it over.------When motor fires stop pushing key in.-----Push key in as needed if motor falters before it warms a bit.-----Do not let motor rev up wildly in neutral.-----Learn how the electric primer valve works , it is not the same as a choke.
 
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