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Johnson 4hp 2000 running/choke/carb problem

H

hamm107

New member
Hi,

I recently got a boat with a 2000 4hp Johnson. It starts using the choke, but if I try to turn the choke off it dies. I can turn the choke about 3/4 off but no further, and it still runs best around full open choke. I have the plastic air box off of the carb right now, and I can see that when I turn the choke off, the engine dies, and fuel drips out of the choke opening (from the throttle body? or from the needle/main jet? not sure).

Spark - I have not actually tested the strength of the spark jumping a gap, but both plugs spark when grounded to the motor.
Carb - fully disassembled, cleaned body, main jet, needle valve, float needle valve and seat (twice). I tested the float valve by blowing into the inlet and when the valve seats I can't blow through it at all, lift up and it goes right through. The float seems to sit just about parallel to the carb housing upside down. Also, when I reassemble with an empty bowl and squeeze the bulb I can hear the fuel squirting into the bowl and when the bulb is firm there is absolutely no noise and I can apply pressure for a couple of minutes and not get a leak of the carb, only leaks when it dies out.

Does this sound like the a cylinder isn't firing, flooding, and then it's dripping back out into the carb through the throttle body? Not sure what is really going on.

Thinking of these next 3 steps... 1. Spark gap test. 2. Carb rebuild kit. 3. Small engine mechanic.

Thanks
 
Also checked compression at around 85, brand new pre mix fuel, and same symptoms using an auxiliary tank or the small tank on the motor.
 
Having to use choke indicates a fuel problem.---Have you tried adjusting slow speed mixture ?----Checked the little orange ( I think ) fuel pump bladder ?
 
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Is the slow speed mixture screw the one sticking out the front of the carb? I did check it, it’s 1.5 turns out. While running (with the choke out) I moved it in both directions and it ran worse and still couldn’t close the choke, so I left it at 1.5. Where is the fuel pump bladder? Is this something near the carb? I had the fuel pump off and checked the screen in it but didn’t see the orange bladder. I saw it in the carb repair kit though but don’t know where or what it is.
 
Just saw where the bladder is on the carb parts diagram, I did not take that out. I will pull it out and check it when I can get back to the motor.
 
I had done all of the work using a remote tank but lastly switched to the little tank on top to rule out any problems with the remote tank hose or bulb but it was no different .
 
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