Mercury 125 wont start :eek:

[STSolecki]

We have a mercury 125 that cranks, starts when u spray gas in the carb, but gets no fuel on its own. We rebuilt the fuel pump today, and still....no fuel. There is fuel in the tank and the primer bulb does tighten up when pumped. We even took the gas cap off to try venting the tank to allow it to pump. What makes the diaphram move? please help us!!! We want to get the boat out at least once this season.

thanks

 

[JB]

Re: Mercury 125 wont start

You need to clean the carbs, STS.

You will save yourself a lot of grief and money if you invest in a factory Service manual.

Good luck.

 

[STSolecki]

Re: Mercury 125 wont start

Could it be an anti siphon valve...cause i watched the gas in the line very slowly go back to the tank. i just dont understand why the pump pulls nothing.

 

[MadProps]

Re: Mercury 125 wont start

I think you are sucking air somewhere along your fuel delivery system, check all the lines and connections

 

[CharlieB]

Re: Mercury 125 wont start

Pumping the primer bulb should fill the carbs and allow it to start.

Pull a fuel line from the pump or a carb and squeeze the primer bulb, if NO FUEL then start checking lines/fitting to find the plugged one and replace it.

I've found quick disconnect fitting missing the little 'nipple' that unseats the ball valve and 'No flow'.

 

[STSolecki]

Re: Mercury 125 wont start

thanks for the ideas, however i still want to know what makes the diaphragm move. I dont see any vaccum lines or mechanical arms that move the diaphragm to start the movement of fuel.

 

[JB]

Re: Mercury 125 wont start

One side of the diaphram is exposed to crankcase pressure/vacuum pulses. that moves the diaphram.

 

[STSolecki]

Re: Mercury 125 wont start

So if that vaccum line is plugged, i obviously wont get pulse from the crankcase. Is that a common problem, or does that lean more towards compression?

 

[JB]

Re: Mercury 125 wont start

Go to "Outboard won't start" in the Engine FAQs, STS. I should have sent you there right away. My bad.

There is a simple fuel pump test there. The rest of the troubleshooting should identify your trouble.

Let us know what you find, and get that Service Manual.