Yanmar fuel supply problem

[Wahoo Sails]

I have a Yanmar 2GM with 400 hours on it. For the second time, it has developed air in the system & stopped running. It has run 40 to 50 hours between doing this. Last time, before bleeding the engine, I installed an electric fuel pump in line ahead of the mechanical pump ... this makes the bleeding process a snap. So far it has been suggested to me that I need a new mechanical pump .... hard for me to believe considering the low hours & the length of time between occurances ... does anybody have any ideas?
Although I could use the electric pump full time, I would prefer to use it only when bleeding ... however, I could be convinced it's better to use it full time.
Bob

[Boracay]

Sounds like you have an air leak somewhere.

Some suggestions:-
1) A worn injector pump (Problem with my old Ford)
2) Leaking secondary filters (I'm going to fix mine one day)
3) Badly fitting hose clamps (replaced all mine)
4) Old fuel hose (replaced all mine)
5) Primary filter (I got a new one)
6) Fuel line fittings (I smeared on some kind of proprietry gunk that I got from my local truck stop when I replaced all my tank and filter fittings)

[Strygaldwir]

I'd check the pressed in fittings on the engine fuel pump. I have 3ym30 engines on my boat and after 24 hours of run time, found I had the same symptoms as you. I reviewed all the fitting and found that the pressed on fitting for connecting fuel lines to the fuel pump were loose. I used some JB weld on them all, and have not had any problems since.

Good luck, fair winds.

Keith

[Charlie]

I had a leak like that when I was doing a delivery once. Engine worked fine then when it got rough or we started motor sailing it would suck air in and then die. Got into Turtle bay and decided that I needed a new fuel pump. The one I had was just a car fuel pump. Took the pump out and found an extra screw laying in the bilge that hadn't been there before. Put the screw back in and everything was fine. Theory is that the screw slowly loosened and let air into the system then eventually the engine would have too much air. My guess is a slow air leak somewhere.

[cal40john]

Maybe this part is obvious, but in case it isn't. If there is air in the fuel system, the leak has to be on the vacuum side. If there is fuel coming out there is a leak on the pressure side. I just went through this on my boat which turned out to be multiple leaks that finally got bad enough to stop the engine. I got a short length of clear tygon tube and hose barb unions. I inserted the tygon in the system in different places to watch the bubbles go by. I disconnected the fuel line somewhere on the pressure side of the sytem and put the end in a container, then turned on the electric fuel pump. There were no bubbles upstream of the Racor filter. I found air bubbles in the line downstream of the Racor filter, so I got a new filter, problem solved there. I then moved the tygon to the inlet on the electric pump, no air there, so it had to be the fitting on the electric pump inlet, or the pump itself. Regooping and tightening the fitting didn't work, taking out the pump did.

For trouble shooting between the electric fuel pump and the mechanical pump in a situation where the electric pump isn't always on, I would start by turning on the electric pump and look for fuel leaks between the two.

On my boat the fuel tank is low enough that the vertical lift is out of spec for the mechanical pump, so an electric pump was added which is on all of the time, but the mech pump seems to work fine without the assist. I will replace the electric pump.

And before someone says it, I did not leave the tygon in my fuel system, it was only temporarily installed for troubleshooting.

John

[camaraderie]

Wahoo...one more possible issue that is easy to check.
Electric pusher pumps MUST have a filter installed between them and the tanks. When you installed yours...did you do it this way? If not...the pump will sound like it is working...but actually be clogged creating the syptoms you describe. Don't ask me how I know!

[never monday]

Wait.
400hrs in how many years old?

[Wahoo Sails]

This motor was installed in 2003. FWIW the fuel tanks sit above the Racor filter which is slightly above the mechanical pump, so the whole shebang is a gravity feed. When I first got the boat, I changed both fuel filters, the Racor showed some grunge on it, but nothing on the filter at the motor, so that doesn't appear to be contributing to the problem.
Bob

[never monday]

Bob,
Which Racor are you using? and how big is your fuel tank(s)? I 'v not seen a CD28 with two tanbks yet. Is there a valve structure between the tanks to isolate one? or do they gravity feed to each other to balance?

[Alan Wheeler]

If the two tanks are on opposing sides of the boat, what happens to the level when you heel. If one tank drains and is now high and dry, bingo.
Another thing to check is the fuel line itself. Ensure there is no restriction anywhere. It could be possible a piece of rust or something is lodged in it or a line has a small piece of weld blocking off the line or anything silly like that.
The other thing is to check the diaphragm in the pump. A pin hole will cause a problem and pin holes are easy to get. Especially after 400hrs.
Although, (Pat correct me if I am wrong) but I thought Yanmars were self bleeding injector systems. ???

[never monday]

Alan,
I'm calling foul on you for stealing the wind out of my sail. That's exactly what I was thinking.

The GM series is not self bleeding.

[Alan Wheeler]

Sorry bout that chief. I know this problem cause I have the same issue if my tanks get too low and I heel over motor sailing. The Perkins doesn't run on air darn it.

[Wahoo Sails]

This CD28 has 2, 12 1/2 gallon saddle tanks, with 2, 4 position valves under the Port tank. I really love the theory of "heeling" being the problem .... problem with that is that I'm on a mooring ball! Until I can get my solar panels up (soon as the wind stops howling) I'm running the engine 1-2 hours per day to run the engine driven refrigeration, recharge the batteries & run the watermaker. Using a 500 series Racor with 10 micron filter.
Bob

[never monday]

Are you just running it out of fuel? 40-50 hrs on 22 gal at idle? Could have a miscalibrated fuel gauge or a short pick up tube. Other than that. Just start at each tank and work your way to the lift pump looking for wetness on the lines. 40-50hrs is way out of the norm for a leak at the engine.

[cal40john]

The fittings at the top of the tank are not under positive pressure, the dip tube and fuel line above the fuel level is under a partial vacuum. Are the hose connections there tight? Is the dip tube welded into its fitting or screwed? How old are the tanks, could there a hole in the dip tube?





John