5 hp johnson won't stay idling

Blogwall

Cadet
Joined
Mar 28, 2011
Messages
9
Picked up an unused 10 year old 5hp johnson. I say unused in that it was bought as an auxilary motor but was never needed. Anyway, problem with it is that it won't stay idling for long. Even with the throttle stop adjusted for a fast tick over, it will die after a minute. When this happens it will only start if you pull out the choke and push it back in immediately. Doesn't seem to matter if the motor is hot or cold. At full throttle it runs fine, the plug is the correct one, is a nice tan colour and not fouled. I stripped the carb and blew out all the jets, but it was spotless anyway. Any ideas?
 

hidef

Lieutenant
Joined
Aug 22, 2009
Messages
1,465
Re: 5 hp johnson won't stay idling

Fuel pump needs a rebuild.
 

Blogwall

Cadet
Joined
Mar 28, 2011
Messages
9
Re: 5 hp johnson won't stay idling

The motor has only done about 5 hours in total. What parts in the fuel pump would go, diaphragm or something? Is there a parts fiche online I can access to suss it out?
 

kfa4303

Banned
Joined
Sep 17, 2010
Messages
6,094
Re: 5 hp johnson won't stay idling

Hi Blogwell. Yeah, the diaphragms can get little tears or holes in them over time and/or be damaged by ethanol in modern gas. Fuel pumps often have a little screen in them to catch debris that can also become clogged. If the motor sat for a while the gas may have gelled up. You may want to clean/rebuild the carb for good measure. If you do find debris in the pump and/or carb passages, I would recommend getting a little in-line, plastic fuel filter. You can get them for a couple bucks at any auto parts store. They tend to be clear and plastic which is handy for monitoring fuel flow. Lots of folks install them in line between the fuel pump and the carb and/or between the gas tank and the fuel pump.
 

Blogwall

Cadet
Joined
Mar 28, 2011
Messages
9
Re: 5 hp johnson won't stay idling

Thanks for the replies. Problem persists. Haven't touched fuel pump yet, but carb passages and jets were spotless, no sign of any residue or varnish. I'll try gravity feeding the carb out of curiosity before I condemn the pump. If the pump is indeed faulty, would it not bog down at WOT?
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 5 hp johnson won't stay idling

You didn't post a model number, so I am guessing we are working on a 2001 engine. When you had the carb off did you make sure all the idle circut passsages where clean, the pilot and main jets were clear.
Squeezing the primer bulb will bypass the fuel pump, if squeezing it has no affect I would guess the pump is ok.
 

freddyray21

Commander
Joined
Jun 10, 2006
Messages
2,460
Re: 5 hp johnson won't stay idling

when running pump the primer bulb to see if it will keep running. I agree it's most likely the fuel pump. The purpose of the fuel pump is to keep fuel in the carb bowl. by pumping the bulb you are keeping the bowl full essentially being the fuel pump. As long as there is gas in the bowl it will run fine even at wot.
 
Top