Johnson 40 won't idle.

Campylobacter

Chief Petty Officer
Joined
Aug 4, 2007
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503
OK, I may be in over my head...

I have a 1991 Johnson J40TLE that came with a pontoon that I'm trying to determine if its any good. It has compression but the cylinders are about 10 PSI apart.

The PO took off the VRO and hooked everything back up without a fuel pump. The controls were also disconnected.

Over the past week I bought and installed a new "regular" fuel pump, and the motor would start, but then would stall immediatly. I then took the carbs apart (they were filthy), soaked Overnight, removed and cleaned the orifice's, and tried again today.

It would start, but it would stall almost immediately without pumping the choke. I tried using the lever on on the controls to rev the engine but no luck. I finally just used the lever on the carb itself and was able to keep the engine running, but only at a fairly fast RPM, when I let it slow it would stall. I was afraid to keep it racing very long, and although it stayed running (about a minute), it was very rough.

Questions: What should I try next? I am guessing since I just attached the controls the idle is way off, so that may be part of it.

I am open to just about any suggestions.

Possibly unrelated question: I have no idea what the knobs on the controller under the key do. What are they and could they be involved?
 

boobie

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Re: Johnson 40 won't idle.

What kind of compression did you get when you checked it ??
 

Bosunsmate

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6,129
Re: Johnson 40 won't idle.

Check that the timing is advancing and the lever hasnt come unattached somehow.
One of those knobs is normally throttle friction
 

Campylobacter

Chief Petty Officer
Joined
Aug 4, 2007
Messages
503
Re: Johnson 40 won't idle.

Check that the timing is advancing and the lever hasnt come unattached somehow.
One of those knobs is normally throttle friction

The timing advance lever is still attached, but it is very difficult to move the whole assembly. I was only able to keep it running by advancing the throttle directly on the carbs themselves so I was not advancing the timing (another reason I was scared to keep it going).
 

boobie

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Re: Johnson 40 won't idle.

When you had the carbs apart did you check the high speed jets in the float bowls ??
 

Bosunsmate

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Re: Johnson 40 won't idle.

The timing advance lever is still attached, but it is very difficult to move the whole assembly. I was only able to keep it running by advancing the throttle directly on the carbs themselves so I was not advancing the timing (another reason I was scared to keep it going).

It shouldnt be very difficult. Maybe something has hardened up in there.
You need to get that moving easily
 

Campylobacter

Chief Petty Officer
Joined
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Messages
503
Re: Johnson 40 won't idle.

When you had the carbs apart did you check the high speed jets in the float bowls ??

I think I did. I followed the instructions in the sticky at the top. I ground down a screwdriver and removed the orifice (jet?), soaked it overnight and then blew it out with air. It looked OK, (the gunk was gone and the to orifice was open). The only other parts I removed was the low speed jet and the float valves and seats. Soaked overnight then reassembled.
 

boobie

Supreme Mariner
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Nov 5, 2009
Messages
20,826
Re: Johnson 40 won't idle.

If you're talking about the timing advance that is under the flywheel that should move nice and free. Squirt some PB Blaster around the base of it and try and free it up. To do it properly the flywheel and ect will have to come off.
 
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