20 HP Johnson Fuel Problem

[jsiiter]

A 20 HP Jonson that runs fine except at prolonged idle (5 to 10 minutes) it quits. The fuel line bulb is soft when this happens. I've replaced the tank, hose and replaced the fuel pump diaphragm to no avail. I'm thinking I have a vacuum leak somewhere. Any thoughts?

 

[ob]

Re: 20 HP Johnson Fuel Problem

Is the fuel tank venting?Is the bulb colapsing after a 10 minute run or just soft?Can you pump on the fuel primer bulb and keep engine running?

 

[jsiiter]

Re: 20 HP Johnson Fuel Problem

Thanks for the reply. This fuel tank is vented. The bulb just goes soft (not collapsed) but I can keep the motor running if I pump it.

 

[ob]

Re: 20 HP Johnson Fuel Problem

Then ,your fuel pump is faulty,you have a fuel leak between the tank fitting and carb inlets,or your carb floats are sticky and need servicing.If the fuel bulb will pump up firm and hold moderate hand pressure before starting,the carb float needles are holding properly and you may not have a leak between the bulb and carb inlets.However ,there could still be a leak between the tank fitting and fuel primer bulb.<br /><br />Considering that your tank and hoses are new,my money is on a failing fuel pump that won't keep up.This is assuming that the engine and tank fuel fittings are sealing.<br /><br />One other thing.Make sure that the fuel pump crankcase pulse hose is connected securely at both ends and is leak free.It's what drives the fuel pump.<br /><br />By the way,what year model 20hp are we discussing?

 

[jsiiter]

Re: 20 HP Johnson Fuel Problem

The motor is a 1989 Johnson tracker. This one doesn't have a pulse hose as the fuel pump mounts directly to the crank case. I think I will thoroughly check all fittings (for the 10th time)and order a new fuel pump to see if that works. Do you think a carb kit with new floats is in order too?

 

[Silvertip]

Re: 20 HP Johnson Fuel Problem

Don't worry about the primer bulb going soft either as that's normal. Fuel is drawn through the bulb and fuel line so after the engine starts there will be no pressure in the line and the bulb will likely never be much more than half full. I agree that you have a fuel pump problem or an air leak.