Yanmar 2GM Fuel Bleed Post Fuel Feed Pump Replacement

[brentbergan]

I have a yanmar 2GM20F engine. The fuel feed pump went bad and was leaking diesel while running. I replaced it. To bleed I opened the bleed screw at the top of the secondary fuel filter and started pumping the fuel feed pump. I saw some bubbles and a little fuel, but never really saw fuel flowing out of the bleed screw, as I would have expected. After about 20 min of pumping, I decided to just try the engine. It turned over immediately. I ran it up and heard no knocking, so don't think there is any air in the line.

Why did I not see full fuel flow out the bleed screw over the top of the fuel filter? Is this normal?

 

[Ralph Johnstone]

Why did I not see full fuel flow out the bleed screw over the top of the fuel filter? Is this normal?

I think it would depend on the level of fuel in the fuel tank. It sounds like you were lucky as the fuel level was about the same as the bleed screw. Any lower fuel level and you would suck in air which would have given you no end of problems.

And please don't ask how I know this .

 

[brentbergan]

The fuel tank was full. Maybe I should look at how the fuel tank sits level-wise to the fuel filter.

 

[Nelsonhow]

The fuel lift pump operates on a cam from the motor. If the motor stops with the cam in the high position when you press the manual lift pump leaver it doesn't go far enough down to fill with fresh diesel from the tank. You can advance the crank shaft manually or with the starter to move the cam.... just a little touch on the starter button will do it.

But on my 1 GM and 2 GM motors (different boats) after changing both the primary and secondary filters I'd fill a small cup with diesel from the primary filer fuel hose that runs to the secondary filter on the motor (I hope I got the primary and secondary right....) This assured that the primary filter was full of fuel with no air. I'd remove the bleed screw from the secondary filter and the us a small syringe (like you used for Epoxy projects... and you can get from West Marine or a drug store...no needles... just the plastic plunger part) to squirt the diesel into the bleed screw hole to fill the secondary filter. A few pumps on the manual lift pump lever and you'd see a stream for diesel coming out of the bleed screw hole. I'd also replace the nylon bleed screw washer each year. If I didn't do this I had to spend a lot of time pressing the manual leaver to fill the secondary filter up. It took to long so I went to the syringe method.

If you advance the crank shaft a few times and still can't get a good stream of fuel when you manually press the lever on the lift pump it a good chance that the internal rubber bladder inside of the pump is bad. I don't know if it can be repaired but a new replacement lift pump is not that expensive and can be purchased from your Yanmar parts dealer on online.

On my 2 GM I added a priming blub in the fuel line between the tank and the primary filter on the engine compartment wall. The bulb is closer to the tank and not in the engine compartment. After I change the fuel filters a few squeezes of the bulb fills the primary fuel filter with fuel. I then remove the bleed screw and a few more squeezes of the bulb and you can see the fuel come out of the bleed screw. The a pump or two of the manual lift lever and you can see fresh fuel coming out of the screw hole and I'm in business. I don't know if this is standard or not but it's been working for 8 or 9 years without problem and really saves a lot of time each year when I do my spring commissioning.

 

[RIVERCRUISER]

Awhile back I changed both primary and secondary fuel filters on my Yanmar 2GM20F engine. Filled the filter housings with CLEAN diesel fuel before reinstalling. Started engine. No bleeding, no knocking, ran fine. Don't recall reading anything in Yanmar manual about bleeding lines when changing fuel filter.

I know that changing the fuel pump is a different animal...

 

[Delezynski]

On our 2GM20F, I also added a bulb just after the tank. Works GREAT and has lasted many years.

One problem I saw in the Sea of Cortez, on a friends boat, was the engine oil filling as the engine ran. Seems that the manual pump, can also leak internal to the engine into the oil system. Just something to keep in mind when working on the system.

I now carry a small bit of hose (to run from manual pump in and out fitting) and a backup electrical fuel pump to install if the problem happens to us.

Greg