1984 Johnson 40 hp

[RetNav]

I went fishing on the flats yesterday and on the way back in the motor cut out, sorta like fuel starvation.
One pump and the bulb was tight.
The vent screw was loose.
The tank is a 6 gallon plastic with new fuel line and bulb.

I could hit the prime and the motor would pick back up and continuing to hit the prime would keep it running. After a few times hitting the prime it started running normally and didn't cut out again.

This is the second time it has done the same thing.

The motor runs rough at idle and sometimes will stop running.

I'm thinking it might be time for a carb cleaning.

BTW the compression is 150-155 on both cylinders.

Any suggestions?

 

[tashasdaddy]

Re: 1984 Johnson 40 hp

i agree with you, besure to the the high and low speed jets. special tool 317002 or make one.

 

[ezeke]

Re: 1984 Johnson 40 hp

Your float valve may be sticking. When you use the primer, it essentially by-passes the carburetor and sends fuel directly to the intake manifold. The vacuum created by the pistons keeps pulling whatever it can through the carbs, but if the float valves stick, the float bowl will empty fairly quickly and all it gets is air.

If the fuel pump failed, there would be no pressure on the primer solenoid line, so the problem probably is not related to the fuel pump.

 

[RetNav]

Re: 1984 Johnson 40 hp

I appreciate the quick responses.

I pulled the carbs, removed the bowls and both are real clean. Of course I can't see in the passages.

BTW, I found two loose connections in the fuel line from the ump to the carb inlets. Would this contribute to the problem?

 

[ezeke]

Re: 1984 Johnson 40 hp

The loose connections could cause air to get in to the system.

Check the action of the floats. The arms of the floats should be connected by spring clips to the valve needle which is where the problems sometimes arise. Normally, the float pulls the needle down as it lowers, allowing fuel to enter. If the needle sticks, fuel cannot get in to fill the float bowl.

 

[RetNav]

Re: 1984 Johnson 40 hp

ezeke, I just pulled both carbs and they are clean and the needle valves work freely. No sticking on either one of them.

I've always heard if gas can leak out air can get in. Could that possibly be the problem? I thought the main problem with loose connections would be between the tank and the fuel pump as that could cause air suction and loss of fuel flow to the carbs.

The main area of leak is on the line from the fuel pump to where it tee's to go to both carbs. A simple fix as the tie wrap is missing there.

The questions are only for my clarification and no intent to insult anyone.

 

[tashasdaddy]

Re: 1984 Johnson 40 hp

if it were sucking air before the pump, i could cause the problem, for it to cause the problem, it would be shooting gas out the leaks, as the pump pressurizes the system. although the pump could be weak also, but i'm still with the jets.

 

[RetNav]

Re: 1984 Johnson 40 hp

I just finished cleaning the carbs and reinstalling them.

There is no leaks now and it does run better, but there is still a miss at idle, though not as bad as before.

I appreciate the suggestions and will keep plugging at it until I am satisfied.

 

[RetNav]

Re: 1984 Johnson 40 hp

I thought someone might like to know what I found on the rough idle problem.

I got two kits and proceeded to tear them down. Under the top plug, right behind the flange, there was two small holes and one of them was plugged with gunk on both carbs. The gasket is a two piece and the small one in the center was almost cut in two pieces. There was no leaks but these two things was all I found. Put it back together and did a sync and fired it up. One of those things was obviously the problem as it runs smooth now.

Thanks for the input.

 

[tashasdaddy]

Re: 1984 Johnson 40 hp

it was running lean, at idle, it takes both holes for the proper fuel/air mix. told you it was the carbs.