johnson 40 starts then shuts off after a few seconds

[damonlbcmiller]

hey guys im new to the forum and need some desperate help. i have a mid 80s model johnson 40. it was recently running like a champ, about a month ago. i went to start it to day and like always it fired rite up, but after a few seconds shut off. i tryed over and over to get it to run like but alsways the same result it would start then shut off, i wouldnt think it would be the carbs due to it running perfect a month ago. i know its not getting fuel but i have no idea why it would do this all of a sudden. any help is welcome and i appreciate anyones input. (fuel pump, carb, vacume leak?) please let me know if yal have had similar problems and what to do thanks

 

[Daviet]

Re: johnson 40 starts then shuts off after a few seconds

Welcome to the forum.
Does the primer bulb pump up firm? Will it continue to run if you constantly pump the primer bulb?

 

[damonlbcmiller]

Re: johnson 40 starts then shuts off after a few seconds

Yes the bulb gets hard and i tryed one time to pump it while i started it but it died again. It has fresh gas and ran absolutely perfect last month which make me believe the carbs can't be the reason becuase I religiously crank it to keep it from gumming up. And suggestions to diagnose a fuel pump if it is the problem. Thanks

 

[Daviet]

Re: johnson 40 starts then shuts off after a few seconds

You can check the fuel pump by disconnecting the fuel line to the carb and crank the engine, you should get spurts of gas out of the line going to the carb.
But, by pumping the primer bulb, you are overpowering the fuel pump. So if that didn't help, I don't think the fuel pump is the problem.
What is your model number so we can look at your engine and try and help you.

 

[boobie]

Re: johnson 40 starts then shuts off after a few seconds

Need a model # ???

 

[damonlbcmiller]

Re: johnson 40 starts then shuts off after a few seconds

I'm not near my boat rite now to get the model number off the motor but I will be this afternoon. I will also try out takin a line off a carb and thanks for yals input. Thanks

 

[damonlbcmiller]

Re: johnson 40 starts then shuts off after a few seconds

The motor is a 85 model the number is j40elcob I pulled a line off the carb and the pump is good but I tried to fire again and it again dies shortly after it idles perfect for about 2 seconds

 

[Daviet]

Re: johnson 40 starts then shuts off after a few seconds

If you have fuel flow to the carb, remove the plug in the bottom of the carb and see if fuel runs out of the bowel when you pump the primer bulb. It almost sounds like it's time to pull the carb and clean it .

 

[likitvi]

Re: johnson 40 starts then shuts off after a few seconds

Does it have electric primer and will it start without it? It sounds like needle valve in the carb is stuck and fuel is not getting into the bowl, or low speed jet clogged. With bowl full of fuel alone the engine should idle quite some time, if it gets fuel only from the primer it should die quite instantly.

You could try priming repeatedly and see if it can made to idle longer. And check that fuel gets into the bowl as suggested, also whether the bowl is empty or not when it dies.

 

[damonlbcmiller]

Re: johnson 40 starts then shuts off after a few seconds

I got into the carbs yesterday and it is apparent I got into some really bad gas somewhere becuase both needles were stuck in both carbs. I haven't ran it yet since I broke a small plastic fuel peice and need new fuel line but will let yal know if it fixed it. Thanks for all the help guys