Tohatsu MFS 4A external fuel does not go in

[Brooklyner12]

Hello Gurus, thanks for being with us on the forum. My question is about recently purchased slightly used 4HP Tohatsu. The problem is the fuel does not go to the internal tank from the external while manually pumped by the bulb I can fill an internal tank pretty quickly with gas and start the engine again.
Even our dealer cannot understand what might be a reason for such "not cooperation".
I found a tiny fuel filter like installed on a hose that connects an external tank connection with an internal tank but I cannot find a replacement elsewhere because nobody knows the part number. I just suppose that small filter looking part could be a problem but may be I'm wrong. Any advise from your experience ?

 

[Sea Rider]

Welcome to Iboats.

Don't know about 4 strokes OB's on 2 strokes same versions, you can't fill internal tank by primmng bulb, not even exploding it, there's a check valve on internal fuel system that doesn't allow fuel filling small tank. If you remove it and mouth blow it, will see that only works one way...

Happy Boating

 

[pvanv]

It depends on which way the fuel **** is set. The check valve (27 in the diagram) is supposed to allow external tank fuel to enter the system. The fuel **** is there to shut off the internal tank. If the **** is set to allow the internal tank to flow, and you pump the primer on the external tank, you will indeed fill the internal tank. Unless the check valve is installed backwards. The check valve prevents the internal tank from draining into the external tank by gravity.

 

[Sea Rider]

Paul, will this procedure work on same 2 strokes versions ? Although have had a 5 OB and plan buying a second one soon, has not occurred doing it. Preffer the hand fill procedure. Check valve allows for fuel not to return to engine connector/outter tank fuel line when small tank's fuel **** is set to open working position.

Happy Boating

 

[pvanv]

Yes.

 

[Brooklyner12]

Thank you Paul again for the diagram and thank you Swa Rider for the reply. Now I know the check valve (27) looks pretty similar ( for me) to a small fuel filter that I was talking about by posting my original post. If that check valve is working one way only and I still can pump fuel manually through it( from external tank), it means the check valve is installed correctly. The puzzle is still remaining : it does not deliver fuel from an external tank. Do you think I have to change that check valve or ........ any suggestion based on your experience and a common sense?

 

[Sea Rider]

Primer bulb must be squeezed with arrow facing upwards, will prime much faster, check, don't forget to set ****'s fuel valve at open position and open both tank's air intakes when priming bulb as suggested.

What's the practical purpose of filling small internal 1.75 Ltr tank from 3 gal tank, you'll need to refill 3 gal tank afterwords. ON my last 5 HP used to fill small tank from 2 gal container and fill 3 gal tank at a service station.

Happy Boating

 

[pvanv]

If the fuel **** is shut off, no fuel goes either into or out of the integral tank.
I have refilled the integral tank that way, if knowing the integral tank will be plenty of fuel for the day, and having a 3-gal. tank available to fill it.