1983 Johnson 20. Lean condition.

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steviecops

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Hi<br />I have a 1983 Johnson 20 that isn't running right. It has a good spark on both, compression is good on both and I've cleaned and rebuilt the carb with a new kit. <br /><br />It won't run at low revs without choke, and even then it sneazes and cuts out every so often. If you push the choke in, it dies right away.<br /><br />There is fuel leaking fron the fuel pump. Would this cause a lean condition? I would have thought that if the fuel pump was drawing air in, it wouldn't pump fuel to the carb at all and the engine wouldn't run even with choke. Also, the air and fuel are metered inside the carb, not on the way to the carb, so I didn't think an air leak before the carb would make the engine run lean?<br /><br />I'm obviously going to fix the leak, but I just wanted to know whether this leak would cause the engine to run lean, or if I have other issues.<br /><br />Thanks<br />Steve
 
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DJ

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Re: 1983 Johnson 20. Lean condition.

Hi stevie,<br /><br />Yes, that could cause your problem.<br /><br />You're right, it is running lean.<br /><br />Is the float level set right?<br /><br />Either way, you need to fix the leak, then retest.
 
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steviecops

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Re: 1983 Johnson 20. Lean condition.

Thanks DJ<br />The float is set right. If I squirt some premix direct into the carb, it idles fine for a few seconds. I'll fix the leak if I can. I rebuilt the fuel pump with a new kit and now it's leaking from between the metal plate and the plastic pump body. It seems like the metal plate is not dead flat. I've had it off and on a few times to try to stop the leak but haven't been successful yet! <br /><br />I can't tighten the two screws that hold the pump on enough because the pump gasket just compresses and splits around the two screw holes. This is stopping me from pulling the metal plate into the plastic body enough. Does that make sense?<br /><br />Might need a new fuel pump.<br /><br />Thanks<br />Steve
 
OBJ

OBJ

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Re: 1983 Johnson 20. Lean condition.

Steve....you sure that's a 20horse?....not a 25? Can you post the model number?<br /><br />Replace the fuel pump gasket. If you have fuel leaking from the fuel pump, either replace it or rebuild it. Did you replace the fuel lines? Old dried up fuel lines can lose their grip on connections and suck air. Might be something to check.<br /><br />Easy way to check the fuel pump, remove the inlet cover. Disconnect the outlet hose and see if you can blow back through the pump from the outlet. If you can, pump is shot.
 
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G DANE

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Re: 1983 Johnson 20. Lean condition.

Hi again Steve. Check if the little keyholeshaped gasket around low speed needle is present and of the newer red silicone-rubber type. Adjust iddle misture by seating needle gently and backing 1 1/2 turn out. Check carb mounting gasket and intake manifold to reedplate to cranckcase housing gaskets, leaks there will give what you have. You did clean carb, including the 3-4 small orifices above throttle butterfly, right ?
 
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G DANE

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Re: 1983 Johnson 20. Lean condition.

I have a bunch of parts floating around in shop. Changing carb alone will bump it up to almost 25 HP, the 20 had nylon limiter in carb. ( non removable, get a 25 or 35 carb )
 
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DJ

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Re: 1983 Johnson 20. Lean condition.

Stevie,<br /><br />It's very possible that metal plate is warped.<br /><br />I still would try to stop all leaks before going any further in the running diagnosis.<br /><br />Good advice too on taking a hard look at all rubber lines and connections.
 
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steviecops

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Re: 1983 Johnson 20. Lean condition.

Thanks for the advice<br />The model number is J20BFLCTE<br /><br />I admit I haven't changed the fuel lines yet, the fuel leak from the pump has kind of distracted me. I have already rebuilt the fuel pump with a new kit. The carbs were cleaned and rebuilt with a sierra kit. Unfortunately, the kit didn't include a new keyhole shaped silicone gasket, so I had to reuse the old one. I did put some silicone around the outside of the gasket though, to make sure it was air tight. I also removed the soft plug to clean the small orifices above the butterfly properly.<br /><br />One thing I did notice was that there wasn't a needle bushing in the carb when I dismantled it, but there was one in the kit, so I fitted it. Maybe I should take it out?<br /><br />I'll replace the fuel lines and get the fuel leak stopped, then post back to let you know what's happening.<br /><br />Thanks<br />Steve
 
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G DANE

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Re: 1983 Johnson 20. Lean condition.

What needle bushing ??? Did you look for the false-air possibilities Steve, sounds like that.
 
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steviecops

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Re: 1983 Johnson 20. Lean condition.

Hi G DANE<br />In the carb kit was a small white plastic bushing, looks like a small cone shape. Apparently it fits over the end of the idle needle before you screw it into place. There wasn't one in the carb when I dismantled it. Maybe this could be causing a problem?<br /><br />I'm going to check everything else tomorrow after I've stopped the fuel pump leaking.<br /><br />Thanks<br />Steve
 
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G DANE

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Re: 1983 Johnson 20. Lean condition.

I dont think that plastic part should be there. If it fits over the needle tip, it will act like a valve when screwed in. Remove it and I think you have iddle again.
 
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steviecops

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Re: 1983 Johnson 20. Lean condition.

Thanks G DANE, I'll take it out. It does have a hole in it that the point of the needle goes through, but I would imagine that it would hold the needle too far out.<br /><br />Oh god, the penny just dropped. It would be like having the needle wound out too far, thus causing a lean condition!!<br /><br />I'll let you know.<br /><br />Thanks<br />Steve
 
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G DANE

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Re: 1983 Johnson 20. Lean condition.

Well not exactly. The fuel is fed around the needle tip. When you turn the tapered needle in, the opening around the tip will reduce and the fuel/airmix will be leaner. If your plastic tip will cover the hole, in stead of fitting into it, you have no fuel passing.
 
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steviecops

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Re: 1983 Johnson 20. Lean condition.

G DANE<br />I thought you turned the needle anti clockwise, ie, out, to make the mixture leaner?
 
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G DANE

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Re: 1983 Johnson 20. Lean condition.

Clockwise is leaner, it meters fuel, not air.
 
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rodbolt

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Re: 1983 Johnson 20. Lean condition.

hello<br /> the 20 HP through hub has a different intake than the 25/35 models and the 20 hp venturi is different as well. someplace there is a tech bulliten on how to identify,by the low speed needle, whether or not your carb uses the small nylon needle bushing. if its there and not supposed to be it may cause problems. sometimes they are tough to get out.
 
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steviecops

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Re: 1983 Johnson 20. Lean condition.

As you say G DANE, it's not through hub exhaust. I took the little bushing out, as rodbolt says, it's a difficult thing to do! I used a long thin screw to screw into the bushing and then pulled it out.<br /><br />Anyway, I rechecked everything as I had the carb apart again, changed fuel lines, etc, and now the engine runs and idles fine. The fuel pump is still leaking, so I'll need a new one. (I'm surprised at how well the engine runs with the pump leaking.) <br /><br />If I had to bet on it, I'd put my money on the problem being caused by that little plastic bushing. <br /><br />Thanks for all the help.<br />Steve
 
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