4 HP Johnson wont start

[jibes138]

My neighbor has a 4 stroke 4 Hp Johnson with internal tank. Won't start or even pretend to start. Took the carb apart and cleaned it up. Put it back and still won't start. A few shots of ether and it started but would immediately stall. It seems like no gas is getting to the carb. Opening the drain on the bowl almost nothing came out. Could the fuel on off switch be bad? Is there a fuel pump on these little guys?

 

[Stu Jackson]

Dave,

Is there a kill switch on this engine?

 

[Don S/V ILLusion]

Dave,

Is there a kill switch on this engine?

Stated differently, is there a malfunctioning kill switch on the engine?

 

[Rich Stidger]

If the kill switch was bad, then the engine would not even run on the ether because the kill switch kills the ignition.

I agree that it sounds like there is no fuel getting to the carb. Pull the hose off the carb and see if fuel runs out. If that checks correctly, then it is an internal carb problem.

It could be a sticking float or float needle. Either of those two items would present with the symptoms you state.

You don't say how old this engine is or how it has been treated, but I have personally found that when buying fuel Stabil should immediately be added. And after using the engine for the day, always close the fuel valve and run the engine out of fuel. Doing this will dramatically decrease the opportunity for the fuel to leave deposits in the carb.

Also, I have a friend who is in the marina business and he services outboards of all sizes. He tells me that the new 4-cycle outboards have such tiny passages in the carb that the only way to clean them is to use an ultrasonic cleaner. This was not the case for the older 2-cycle engines where you could use a carb dunk solution to effectively clean a clogged carb.

So if this engine has been subjected to having fuel left in the carb for long periods (over a month) and the rest of your troubleshooting eliminates the fuel supply external to the carb or to the float and needle valve, bite the bullet and pull the carb. Get it to a knowledgeable mechanic who can ultrasonically clean it. If the mechanic says that a ultrasonic cleaning isn't necessary, move on.

 

[jibes138]

The float bowl had some solidified gunk that I cleaned out so it clearly is in poor shape. The float and needle valve moved freely but I didn't take the float off. One problem with internal tanks is they draw from the lowest point on the tank any water or debris goes right in the fuel system. I told him to bring it to someone. Any further disassembly on the dock risked losing parts and tools.

 

[Jerry Clark H356 SV Persi]

I had a 4HP Yamaha that ran great until ethanol gas came along. I had a carburetor rebuilt, then replaced, them rebuilt twice, then I cleaned it, took off the carburetor and had it cleared ultrasonically, then got rid of it and bought a Lear 5 HP propane. Save yourself about $500 worth of repairs and get rid of it and buy a propane or electric motor, or wait until Trump is president and maybe we can get some real gasoline. I used Stabil and that didn't help. Even non ethanol gas has additives that make these small carburetor jets clog up.

 

[jibes138]

The only thing that seems to work is to run them every single day and that is pretty impractical for most people. I have a small skiff with a 20HP Yamaha and I've even had trouble with that carburetor. It runs great as long as I use it all the time. The minute it sits for a few weeks it runs bad again. Every time I use it I empty the fuel tank and put in fresh gas, the old gas goes in the car or lawn mower. I'll post what my neighbor finds with his, it is now with a mechanic waiting in queue for repairs.

 

[Zed]

The only thing that seems to work is to run them every single day and that is pretty impractical for most people. I have a small skiff with a 20HP Yamaha and I've even had trouble with that carburetor. It runs great as long as I use it all the time. The minute it sits for a few weeks it runs bad again. Every time I use it I empty the fuel tank and put in fresh gas, the old gas goes in the car or lawn mower. I'll post what my neighbor finds with his, it is now with a mechanic waiting in queue for repairs.

WE HAVE A LOCAL MARINA that sells ethanol free gas. Everyone also runs Blue Stabil as a support to that. You can also get Aviation fuel, if you sign a paper that says you are only going to use it for aviation purposes.