Carb problem.

Before rebuilding the carburetor on my 56 Johnson 10 hp, the motor would start only after injecting fuel directly into the carb and would run only as long as that shot of fuel lasted. I ordered a rebuild kit and installed it word-for-word per the Johnson manual. Also made adjustments on the high and low speed mixture valves per the manual. However, I'm right back where I started. Will not even try to start without injecting fuel directly into the carb.
Obviously a fuel feed problem but darned if I know why.

Any ideas?

You are using a pressurized tank?


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The motor has been converted to a single line system with remote pump. I can see the pump refill the fuel bowl so it appears to be working.

Low speed is pretty small hole, I’ve had to do carbs more than once before.


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The high and low needles, seats and passages were well cleaned and blown out with compressed air. Maybe there was trash I didn't find that washed down after assembly.
The low speed mixture is set to 1 1/2 turns per manufacturer instructions. Suppose that's too lean? I've tinkered with that in and out and it didn't seem to make any difference.

Twist that screew first. 1.5 is the ballpark initial setting but it does sound like somthing else may be going on.

I'll give that a try. If the fuel bowl is full, it should be just wanted short trip up the venturi tube to the intake air flow. I think that needle valve is the only thing between the two.

The glass bowl you're looking at is only the filter. it sounds like your float bowl isn't filling.

Look at your parts diagram.

Make sure the metal filter #63 allows fuel to pass through it... it's possible it can get totally blocked. Soak it in lacquer thinner and blow it with air.

Then you have to make sure your float bowl valve is working. #59 can get stuck in the up position. The float can also get stuck so that it can't fall down and open the valve.

Sounds to me like you need to remove the carb and make sure that's working properly. Float should be adjusted too so that it's even with the casting when it's upside down...

I've tried it without the filter. Didn't make any difference there. The float and the float valve are new, but that doesn't mean they can't get stuck. I'll try that next.

It can be a bit tricky to see... the float might work without the bowl attached but when you attach the bowl it can bind the float.... sometimes the gasket protrudes inside.

when you move the float the valve should fall down and ride on the tab... was there a small spring to attach it to the float ? Most older motors don't have that.

Hmm, now that you mention it, there was some kind of little wire Gizmo that came with the new float valve and seat. There wasn't one before and I could find it in the instructions or parts listing so I didn't install it. Have to see if I can find the little rascal.

Yep.. that's it... new valves are lightweight. They need that spring dealio to help the float pull it open...

this shows how it's attached:

https://www.outboard-boat-motor-repair.com/Johnson/Evinrude%20Johnson%205.5%20HP%201954-1964%20Carburetor%20Tune-UP.htm

I pulled the carb off and broke it down. Found the problem was a case of D. A. on my part. The float was installed upsid down. That got gads moving, but now I have the opposite problem. Every time I pull the starter cord, gas runs out the front of the carb. High speed mixture was set to manual specs, but when I closed it off completely, the gas stopped running out the front of the carb.

Ok now it’s not closing. Worth checking one more time to be sure the float is free to move. If so then I’m thinking it’s that big pump. Maybe it’s overpowering the valve?

Could an oversized fuel line from the pump to the carb cause an over-pressure condition that would over-power the valve? That line is supposed to be 1/8" but I didn't have any on hand so I used 1/4" until I can get to the parts house.

It's possible.. that's a 30 hp fuel pump... but the other thing you can check is the float level.. it's possible you bent the tang significantly... Look at this guys photo for how the float should look when it's upside down... did you do that adjustment?

https://www.maxrules.com/fixtuneitup2.html

Yes, I did do that adjustment. I've wondered about that 1/8" fuel line. That's what is used on my 25cc weed eater. Seems awful small for a 10 horse. Like it was some kind of a "restrictor" or something..

You could try running it with the pulse line disconnected ? But I agree with Pappy. Take it apart again and triple check everything.

Try blowing through the fuel inlet to the carb with the carb upside down. Ya should not be able to blow through it upside down.