1975 Johnson 6 H.P. Engine starts then dies, Please help

[General Stuart]

Hello
I have had this 1975 Johnson 6 Horsepower engine on my John Boat for about Five years now. It has never missed a beat all the time I have owned it and run out perfectly. Last week we launched it and it did not want to stay running. it would start right up when choked and seemed to run fine until it wormed up a bit then, it would die. I felt perhaps the gas may have some water in it so I dumped the gas and added fresh gas to it which made no difference, it would start right up when choked then die if I tried to pull off the choke. We Loaded it and went home.


Yesterday I got back into seeing if I could find the problem with it. it started up fine cold and ran good for about Three to four minutes even taking off the choke, then it would die. When I would get it running and it started to die, even if I gave it a shot of either it would still die. That led me to think it may be ignition parts so I Pulled the fly wheel and replaced the two set's of points and condensers. I made certain I had them gaped at . 020" and put it all back together. it did not change a thing it still started right up choked then died after about 15 seconds. I then took off the fuel pump and took it apart. The diaphragms all looked fine and there was not much junk in it, so I put it all back together being careful to get all the springs and gaskets back the way I found them.




I then removed the fuel line going to the Carb. and pulled the engine over. it squirted a good bit of gas out of it's fuel pump. I bought a Carb. rebuild kit and took the carb. apart. I did not see any garbage inside the Carb, but used a can of Gumout to blow through all the air Passages and they all seemed clear. I set the new float level and put it back together and bolted it back on the engine.



I cranked it up choking it, and it did not change a thing as it still run's for about Ten seconds then dies before it gets warm or I can take the choke off. It seems to have good strong compression and the spark is bright blue Is there a chance it may be the Crankshaft seal ? I appreciate any help I can get here, it is very frustrating at this point. Best regards, General Stuart

 

[Will Bark]

Re: 1975 Johnson 6 H.P. Engine starts then dies, Please help

Stupid question, but is the tank vent open? Are all the fuel connections airtight? Did you check the screen on the fuel pickup in the tank? Did you remove the welch plug on the carb and clean out the 3 holes under it which is the idle circuit? Did you make certain the float was level when the carb is turned upside down? Is the float needle dropping down when the carb is upright? Those are some of the things I would check before looking at the crancase. Good luck.

 

[OptsyEagle]

Re: 1975 Johnson 6 H.P. Engine starts then dies, Please help

It sounds like it is a fuel restriction, either the carb or the fuel line. The fuel line is easy to check. Run the motor. Just as it is about to die, squeeze the primer bulb. If it regains itself for another 10 seconds, then it is a restriction in your fuel line. Since your pump is fine, it is most like the vent as Will indicated or your fuel line's check valves. If you have another fuel line for your tank you could try that.

If the motor does not regain itself after sqeeezing the primer bulb, it must be a dirty carburetor.

 

[General Stuart]

Re: 1975 Johnson 6 H.P. Engine starts then dies, Please help

Stupid question, but is the tank vent open? Are all the fuel connections airtight? Did you check the screen on the fuel pickup in the tank? Did you remove the welch plug on the carb and clean out the 3 holes under it which is the idle circuit? Did you make certain the float was level when the carb is turned upside down? Is the float needle dropping down when the carb is upright? Those are some of the things I would check before looking at the crancase. Good luck.

Hello Will
I have soaked the Carb in carb cleaner solution and installed a Rebuild kit in it. The float and needle and seat are new and level, they are going up and down with no issues. I did remove the welch plug on top of the Carb and cleaned and made certain that all Four holes were clean and clear. There was hardly anything of foreign material in the carb when I took it apart. I changed out the dual Points and condensers. I Gapped them at . 020" as the Johnson dealership where I got all the OEM Part's told me to do. The spark is bright blue. I did notice after cranking several times on the engine the spark plugs are not getting wet with Gas as they should with the choke pulled all the way on. This Leads me to believe it may very well be a crankshaft seal that has gone bad. I had a similar situation one time with a Snowmobile engine that was a Twin cylinder Two stroke engine that acted similar to this and that turned out to be a bad crankshaft seal as it was leaking and would not allow proper vacuum inside the engine to pull the fuel from the Carb into the engine. Has anyone else here had to replace a crankshaft seal in the past and were the symptoms similar to mine ? Thanks General Stuart

 

[OptsyEagle]

Re: 1975 Johnson 6 H.P. Engine starts then dies, Please help

I would think that a bad crankcase seal would only cause problems on one cylinder, not both and would cause you difficulty in starting as opposed to starting fine and then stalling about 10 seconds later.

The starting and running for about 10 seconds and dying seems like it is getting a full bowl of gas when you squeeze the primer but the carb is not getting anymore after that. Once the carb bowl empties your done.

That is why the squeeze test just before stalling is a good test. Since you confirmed that your inlet valve on the carb is not sticking and your fuel pump works fine, if it keeps the motor running when you squeeze it and if it still wants to stall when you leave the tank cap open (confirming that it is not a tank venting issue) then it is your fuel line. That is how I see it.

I would certainly check that before I pulled the entire powerhead to fix your crankcase seals.

 

[Rick.]

Re: 1975 Johnson 6 H.P. Engine starts then dies, Please help

Well I'm not that familiar with your engine so I am reluctant to give advice. But your symptoms are indicating your cylinders aren't getting fuel from the carb. Your right, I could be a crank seal but the likelihood is your carb. is the problem. It is not uncommon to have to clean a carb. more than once. After cleaning every passage should be blown out with compressed air. Before I would suspect the crank case seal I would suspect the reeds but even then that would be unusual. Have you set the slow speed needle correctly for start-up? Perhaps give it another 1/4 turn out from factory spec. until you get it running enough to set it properly. Best of luck. Rick.
P.S. you might want to keep an eye on this post and see how it gets solved. http://forums.iboats.com/showthread.php?t=482545

 

[General Stuart]

Re: 1975 Johnson 6 H.P. Engine starts then dies, Please help

Hello
The upper Carb assembly has been sitting in Hot Carb. solution cleaner for 6 days now. I took it out and noticed that the very small hole in the upper portion of the Carb. towards the Outer flat section that meets the bowl assembly and Gasket that this tiny holes goes from there into the Main Jet area & is now free as air blows through it. I found that the smallest Torch tip cleaner I have in my Multi set fit's that hole so I ran it back and forth through it's extensive contoured channel till I could see it in the Main Jet area. I now have it back together and hope to get it bolted back on my engine tomorrow when time premits to see if this was indeed a Carb. related issue. I will respond with the results once the Carb. is bolted back in place. Thanks, Kurt

 

[Daviet]

Re: 1975 Johnson 6 H.P. Engine starts then dies, Please help

Be careful not to change the size of those holes, they are calibrated tothe engine.

 

[General Stuart]

Re: 1975 Johnson 6 H.P. Engine starts then dies, Please help

Be careful not to change the size of those holes, they are calibrated tothe engine.

Hello Daviet
I figured that and the use of the Torch tip cleaner was done to just insure the passage way was clear. It is a complex passage from this very small hole to the Main jet area where it ends up but being that the Torch tip cleaner was so tiny it allowed it to bend and turn through the complex channel it takes to get to the Main Jet area. I hope to have the Carb. Back on the engine tomorrow and sure hope this solves the Non-Running issue I have been having. I further feel that this New form of Gas they have come out with the Ethanol added to it is a hindrance and Takes away the octane and self life of this Lousy gas they are selling us there days... Regards, Kurt

 

[Daviet]

Re: 1975 Johnson 6 H.P. Engine starts then dies, Please help

There should also be some very small holes under the core plug going straight down into the carb venturi, are those clean also?

 

[General Stuart]

Re: 1975 Johnson 6 H.P. Engine starts then dies, Please help

Hello
I got the Carb. back on and started it. It ran a little rough at first then smoothed out as it warmed up. I adjusted the low speed needle valve and it run's as smooth as glass like it used to before all this issue happened. It starts warm now with one pull and cold with Just two Pulls. Time to get back to Fishing thanks, General Stuart