79 140hp Johnson hard start

baydaze77

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Sep 13, 2007
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I have a 79 140hp V-4 Johnson. The motor has sat for about 6-7 months. The motor started, then immediately died. Now it will not start. The primer bulb is firm, the fuel pump is fairly new, and the carbs were rebuilt shortly before the motor sat. I'm thinking its just flooded, but not sure. Does anyone have any tips on what else it could be?
 

tashasdaddy

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Nov 11, 2005
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51,019
Re: 79 140hp Johnson hard start

report back what you find,
 

baydaze77

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Sep 13, 2007
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Re: 79 140hp Johnson hard start

I was able to start the motor using a portable gas tank. The motor started right up and ran great. I was told it could be a problem with the vent on the inboard gas tank. I checked the vent line, it seems to be free of any obstructions. The fuel coming from the hose seems to be very clear and has almost no gas smell at all. I'm wondering if there may be water in the tank. I think my best bet would be to pump out the tank. Any suggestions would be great.
 

ezeke

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Sep 19, 2003
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12,532
Re: 79 140hp Johnson hard start

Unless the vent is corroded shut on a inboard tank, that is almost never the problem.

The pickup occasionally gets clogged because it is at the bottom of the tank.

The anti-siphon valve is very often the problem.

Installation of a full sized water separating fuel filter will deal with the water-in-the-fuel problem.
 

baydaze77

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Sep 13, 2007
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Re: 79 140hp Johnson hard start

I have a full size water seperator installed. Where is the anti-siphon device located? Would I still be able to prime the bulb if the anti-siphon or the pickup were the issue? Also, would pumping out the tank be the best action there is water in the fuel? I'm trying to resolve this issue before the start of the Chesapeake Bay fall striper season, so I'm desperate for answers. Thanks again for any help.
 

ezeke

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Sep 19, 2003
Messages
12,532
Re: 79 140hp Johnson hard start

The filter can be dumped as often as you want or some models have bottom drains.

Coast Guard regulations require that built-in tanks have anti-siphon valves on the outgoing fuel fitting, where the outgoing fuel hose is connected. This is to prevent the fuel from being siphoned from the tank if there is a leak at the hose or engine.

Most anti-siphon valves are of the type that have a ball bearing with a spring. The older ones are designed for inboard type installations, not outboards, and they are not designed for today's fuels. In addition, they are prone to sticking, causing poor fuel flow.

Regardless, the fuel system has to overcome the pressure of the valve in addition to lifting the fuel.

The bottom line is that if all of the outgoing fuel lines and the engine are higher than the top of the tank, the anti-siphon valve can legally be removed. If not, it is good practice to replace them with the newer ones.

If you take the tank fitting off and find that there is no valve inside of it, you can move on to the fuel line and bulb and so on.
 
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