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1992 25 hp Johnson fuel pump.

T

Taylorsville

New member
So I was on the lake last week and the motor would run great on low speed but when I would WOT is would run really sluggish unless I would keep pumping the bulb by hand. Got it home took the fuel pump apart and I found it had a mangled spring so I bought a new pump. I am almost 100% that it’s the fuel pump that is making the motor run this way what do you guys think?
 
Repair kits are available for the pumps and it is a lot cheaper to fix them.---------------If operating the manual fuel pump kept the motor running then I think you found the smoking gun.
 
I was going to go the repair kit but it did not come with the sprimg that was damaged so i had to buy the new pump. thank you for your reply.
 
OKAY HERE IS THE DEAL. I have had this 1992 25 hp for 2 years now and it has been given me guff ever since it will not let me go WOT without having to prime the bulb. Here is what I have done. Check spark it is great installed new Champion spark plugs, new coils, new spark plug wires,rebuilt caborator 2 times, new fuel pump, new hose and bulb, checked compression 110 psi each side, cleaned fuel tank new fuel, new impeller, new thermostat but still I have to pump the bulb to get it to WTO. It will let me go half throttle fine and will start first pull every time.

What can it be I am kind of getting sick of buying stuff for this motor. Today while running the bulb is just soft unless I pump it. I also took the fuel cap off to make sure it was venting.
 
These motor are quite well built and rugged too.----------You need to check the reed valves and possibly it has a bad lower crankshaft seal.-------------Throwing parts at the motor is not a good trouble shooting method , but that is my honest opinion.------Having to operate the manual fuel pump indicates that there may be a crankcase compression issue !
 
Crankcase compression and cylinder compression are a totally different thing !------------A broken / open reed valves would give you little or no crankcase compression and still good cylinder compression !------------When compression occurs in the cylinder then the reed valves open to allow fresh air and fuel into the crankcase.-------U-tube has tutorial videos ( some better than others ) and they will help with the understanding of this concept.
 
The primer on the manual start models is a wee pump.---It pulls gas from the carburetor and squirts it into the intake manifold for starting.------------The knob must be fully in for normal running.------You can do a test by blocking off the discharge to the motor when it is running.
 
Reason I have asked about the primer is I bought an owners manual and have been reading about the fuel system. When you say block the discharge would that be from the carburetor to the primer line? I was thinking of clamping it shut while running the motor.
 
Vice-grip on line from carburetor to the pump .-------A very good / cheap method of testing.------Always test stuff before spending money.
 
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