Johnson 1972 9.5 Carubetor Issue

[Ryan756]

I have a Johnson 1972 9.5 horse (9r72m). I recently got it back from a friend who had it running last time he used it. Now i cant get any gas to pass through the carburetor. I took the carb apart and cleaned it well even though it was not dirty. I sprayed carb cleaner through the main jet and idle holes to make sure they were free of obstructions. I also replaced the Float, needle, and needle seat. I even tried putting the carb together with out the float and gas just comes a float chamber over flow hole at the top of the carb housing. Ive tried everything but no matter what i cant get gas to come out of the main jet and idle holes in the carb. I removed and cleaned the slow speed needle ans I even replaced the fuel pump. The engine starts right up when gas is poured into the top of the carb. Please help ive been stumped on this problem for 2 weeks now and i cant figure it out.

 

[wmk0002]

From what you have said, fuel delivery to the carb seems to be ok since the bowl fills and overflows without the float installed. Likewise, if the engine runs when you pour gas in the carb throat it means you have compression and adequately functioning reed valves which are needed to draw in fuel/air mixture.

My best guess is that the float is set incorrectly and not allowing fuel to be primed or pumped into the bowl.

Are you also choking it and advancing it to the fast idle position when starting it? I have the same motor and it always requires this to be done when cold starting it, even in warmer temperatures.

 

[Ryan756]

Ya i choke it and put the throttle to fast/start. But gas never comes out of the carburetor.

 

[perchjerker]

sounds like the float is not properly adjusted.

Can you take the float bowl off after you pumped it up and see if there is any gas in it?

 

[Ryan756]

The float bowl is full every time i take it apart after priming it. The large core plug is pushed in on the side of the carb. Would this make a difference? If some one else has this motor can you check your carb and look at the core plug to see if it is flush or pushed in. The part is number 18 on the carb diagram sheet.

 

[perchjerker]

have you verified that the passages in the carb housing (body) are clear (not the jets, the aluminum housing itself)?

 

[Ryan756]

I have checked the passages on the float chamber and there clear. What drives the fuel pump? I unhooked the line going into carb and poured gas into carb to fire it. When it ran for a second the pump looked like it was pushing gas but not very hard. When its all together i prime the bulb till its hard and i cant squeeze it anymore but never see any gas exit through any of the jets. When the bowl fills with gas. I the gas that is in the bowl sucked out or pushed out by pressure?

 

[Ryan756]

Should the motor be pumping water through it when it idols in neutral? I when i fire it for a second water is not coming out the bilge hole.

 

[perchjerker]

you need some schooling on small engine repair. I will try

First off, the fuel pumps job is to supply the carb with fuel, not to pump fuel through the carb. Fuel gets from the carb bowl into the cylinders from whats called the venturi effect, a vacuum develops from the pistons pumping and this draws fuel through the carb passages as air rushes past the opening in the jets and draws gas into the cylinders.

The fuel pump is run off of impulses in the cylinder block from the pistons pumping. There is either a impulse line going from the block to the fuel pump or there is a passage between the two. The fuel pump doesnt really crank out a tom of fuel, just enough to keep the carb full.

On the water pump, you wont get any pumping until the engine is running. It takes a few seconds for pressure to build up and water to flow through the motor before you will see it out the tell tale hole. Dont call it a bilge hole. The bilge has nothing to do with the motor, might as well use the correct terminology.

From your questions I have my doubts if you really know how to clean the carb and verify there is no blockage in the body, not trying to offend you, I just dont think you are well versed enough in this.

 

[FormerParatrooper]

I had the same issue when I rebuilt the carb on my Johnson 9.5 MQ13.

I did not properly align the float. I also lost the little clip to the needle valve. Once I got the clip, and adjusted the float properly, I have not had any more issues. I used leeroys ramblings to get the float set right. https://www.leeroysramblings.com/OMC_9.5.htm His adv ice on these motors is geared towards having some mechanical knowledge, but it is very easy to understand.

We all have to start the learning process somewhere and from what I have read on this board has been excellent and has helped me check into things I would not have thought of before.

 

[Pappy]

Been watching this one.
Perch is providing you with good information.
For those who seem hooked on the float height the height, for this issue, can be way off and with an idle needle the engine can still be adjusted and the engine will run.
You asked whether it is pressure or vacuum that gets the fuel from the float chamber to the engine. It is vacuum. "Bernoulli's principle", look it up.
I would start with purchasing a complete kit for the carburetor. An OEM kit since that is the only kit that will be absolutely complete.
You are either missing a nozzle well gasket or you have NOT cleaned an idle passage properly.

 

[Ryan756]

Thanks for the help guys. Everything is good with the carb. I narrowed it down to a vaccum problem. The gas is not being sucked out the carburetor. Im going to check the diagram sheet to look well nozzle gasket cause the only one that is there is the gasket between the float chamber and body. I did lose my clip that connects the needle to the float. And ALL passages are clean. I'm very mechanically inclined i just needed a little help with understanding how the whole system worked. Thanks for the run down perch. I will let you guys know now this plays out.

 

[Ryan756]

I cant find a well nozzle gasket let alone see the well nozzle in the diagram. The complete carb kit 382048 looks like it might have one but i'm not sure. Does anyone have any input on the matter?