Locate fuel obstruction?

[pnwguy]

94 Johnson 175hp VRO. Smokes like a chimney. I searched some posts and found that the cause could be over oiling due to an obstruction or air in fuel system. I replaced the bulb and line from the water/fuel filter to the engine. Have checked all fittings from the tank to the VRO/fuel pump. All seems in order. I was running the engine at idle this evening and was getting my normal amount of smoke. I decided to check my bulb and noticed it was not hard, I was able to squeeze with medium pressure and noticed the my engine idled smoother and smoke all but dissapeared. Once I stopped sqeezing bulb, engine returned to rough idle and more smoke. Repeating the process produced similar results. I am now convinced I have issue in the fuel line but cannot locate the problem. Any suggestions?

 

[Vic.S]

Re: Locate fuel obstruction?

Don't know VRO systems but if you pump gas through with the bulb won't that mean that because the fuel pump is pumping less gas it will pump less oil. That'll stop it smoking.

If there was an obstruction surely the engine would show all the signs of fuel starvation and not achieve full power or revs.

I'd be looking at the fuel pump as the cause of the trouble but I'd want to know a bit more about the way it works before replacing it!

The bulb wont stay hard although if it is flat that would indicate a restrictionat the tank end of the line

Sorry not really much help just thoughts probably rubbish anyway!

 

[Reggie08]

Re: Locate fuel obstruction?

It could be your carbs need to be cleaned and rebuilt.

 

[Chris1956]

Re: Locate fuel obstruction?

Make sure the fuel screen or filter on the motor is clean, and the oring/gaskets are good. Any air that leaks into the fuel line will cause the motor to pump more oil. Make sure all other filters are clean. Make sure the tank vent is clear. Make sure the anti-siphon valve on the fuel tank is clean.

 

[dimock44]

Re: Locate fuel obstruction?

Agree with Chris. Remember there may not be enough pressure on the fuel system to see a leak but it can suck air with out leaking. This causes the amount of gas to be less. The oil side of the VRO pump does not know this and keeps pumping the same amount. The applies to the oil lines also . Any air leaks will cause less oil to be pumped and is bad for the lube of your motor. Its easier to suck air than either oil or gas.