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post #1 of 24 Old 06-04-2016 Thread Starter
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Yanmar 2GMF Fuel Mystery

I can hand prime with the lift pump the secondary and injector pump bleed screws. Engine starts and runs for 3-4 minutes then stops.

The secondary fuel filter cup is almost dry. The engine uses the secondary filters fuel and stops when its empty.

I have replaced fuel lines, primary fuel/water separator, new lift pump
filters and have spent much time looking for leaks etc.

It was suggested that the lift pump arm goes under the cam inside the engine. I have the new lift pump arm against or on top of the cam. What is correct?

It seems the lift pump is not pumping fuel to the secondary fuel filter as the engine runs.

Any help will much appreciated, Thanks!
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post #2 of 24 Old 06-04-2016
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Re: Yanmar 2GMF Fuel Mystery

Do you have the old one there should be an obvious rub spot on the arm usually they are flat on one side and its obvious how it goes in.
If you can turn the motor by hand or crank there should be different amount of travel in the prime lever as you move the motor (and the cam) my guess is the arm is on the wrong side buy the pump could be damaged if installed incorrectly.
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post #3 of 24 Old 06-05-2016 Thread Starter
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Re: Yanmar 2GMF Fuel Mystery

I have the old pump and looked closely last night, the cam wear spot is on the bottom of the arm so the pump lever is bumped up to pump?

The new lift pump hand primes fine to bleed the system. The engine starts and runs for 2-3 minutes then stops. Looking at the secondary filter container its empty. Fuel is not being replaced by the lift pump.

The photo shows the old lift pump upside down.

Any help is appreciated
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Lift Pump Cam Wear spot on Arm.JPG  
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post #4 of 24 Old 06-05-2016
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Re: Yanmar 2GMF Fuel Mystery

Start with the basics. Is the lobe on the cam still present? I have had other engines with soft cam lobes that wore down to where they would not open a valve. Is the lever shape and length the same on the new pump as the old? If the new pump works when you manually operate it then the problem has to be with the lever and lobe when mounted on the engine unless you have an air leak that somehow opens up when the pump is mounted but not when you are manually operating it.
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post #5 of 24 Old 06-05-2016
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Re: Yanmar 2GMF Fuel Mystery

While a worn cam lobe is possible, a fuel line air leak is more likely. The smallest pinhole/fitting air leak will cause fuel flow to stop. Check the line from tank to engine VERY carefully, especially at elbows or fittings. Run directly from a container to see if the same problem persists. There are electric lift pumps available to use as back-up. I keep one aboard as an emergency option. Also, make sure the second bleeder at the injector pump is not ajar and that you've bled the air out from that point while using the primer arm.

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Last edited by smurphny; 06-05-2016 at 09:48 AM. Reason: more info
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Re: Yanmar 2GMF Fuel Mystery

Quote:
Originally Posted by Capt Mulch View Post

It was suggested that the lift pump arm goes under the cam inside the engine. I have the new lift pump arm against or on top of the cam. What is correct?
For "most" Yanmar engines the lever arm of the lift pump 'rides' ON TOP of the cam/PTO shaft.
To verify in your situation, remove the cover for the rubber diaphragm and rotate the crankshaft with a socket wrench while watching the diaphragm to move up and down (of course with the decompression lever system 'engaged').

Question ... with all the fuel system rebuild you've recently accomplished, is the tank valve still 'closed'?
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post #7 of 24 Old 06-05-2016
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Re: Yanmar 2GMF Fuel Mystery

It could be leaking air at the bleed screw on top of the secondary filter. That little plastic washer is not all that robust and neither are the aluminum threads that the steel screw relies on.

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Re: Yanmar 2GMF Fuel Mystery

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Originally Posted by smurphny View Post
While a worn cam lobe is possible, a fuel line air leak is more likely. The smallest pinhole/fitting air leak will cause fuel flow to stop. Check the line from tank to engine VERY carefully, especially at elbows or fittings. Run directly from a container to see if the same problem persists. There are electric lift pumps available to use as back-up. I keep one aboard as an emergency option. Also, make sure the second bleeder at the injector pump is not ajar and that you've bled the air out from that point while using the primer arm.
Agree as to a 'leak' as the most probable cause.

The easiest way to assay for the validity of a leak is with a vacuum gage and vacuum pump and a k*****-valve between the vacuum source and the evacuated tubing, etc. Evacuate (pull vacuum on the fuel delivery line) close the k*****-valve (and shut off the pump) and record the vac. gage reading. Go drink a few/many beers; then, read the vac. gage. If less vacuum on the gage than when you shut down, then air LEAK.
An alternate is to install a small electric inline diesel fuel pump, ****-valve and Pressure gage near the tank, etc. as above ....... and then simply look for the 'wet spot'.

During your system 'rebuild' if you used 'compression fittings' - very poor choice for vacuum/pressure-tight service.


*k**** - sorry, in a PC frenetic world all words that are composed of the letters C-O-C-K apply only to 'penises' and are thus banned.
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Last edited by RichH; 06-05-2016 at 01:57 PM.
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post #9 of 24 Old 06-05-2016
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Re: Yanmar 2GMF Fuel Mystery

you could be starving for fuel,check vent line, remove fuel cap and see if will run.fuel arm on top of cam lobe.
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post #10 of 24 Old 06-05-2016 Thread Starter
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Re: Yanmar 2GMF Fuel Mystery

Thanks to everyone for the help!

Heading back to Rhode Island tomorrow

Summary, the secondary bleed screw washers, plastic and copper are new. The new fuel valve shutoff is at the Racor 120 filter and is in the flow position.

The fuel tank outlet is at the top of the tank, don't think there is a shutoff valve at the tank. I did relocate the primary for better access, sight and filter change, could this be a problem? I also pumped all old fuel from the fuel tank last fall and have 3/4 full of fresh diesel.

We removed the fuel fill cap, no suction that could mean blocked vent. I also cleared the transom fuel vent with a piece of weed wacker line.

Plan, setup a separate tank of fresh diesel and feed the inlet on the lift pump directly. Bleed secondary and injection pump,should I also bleed the two injectors? Start the engine. If it runs for more than 2-3 minutes I'll have more information. Thanks to all! Mike
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Fuel Tank Outlet.JPG   Racor 120A Fuel Lines.JPG  
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