Gordon, I recently replaced the fuel filter mounted on my 2 cylinder 18HP Yanmar diesel as well as the Racor fuel/water separator. While I filled up both cups before reassembling, I am pretty sure that some air must now be in the line. When I try to bleed the line by use of the manual fuel pump mounted on the side of the engine with the bleed screw on the fuel filter opened and the throttle at half speed position, no fuel comes out of the bleed hole. Now my top RPM seems to be about 3100 whereas before it was 3800. Does this seem to be a result of air in the lines? If so, why can't I bleed the lines using the manual pump? What to do? Regards, Ed
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Claude L.-Auger
Bleeding in stages
Did you pump and bleed the Racor after putting in the new filter ? If not you still have air in the system. Then when you open up the 10mm screw on the filter and pump manually, you should get air bubbles and good fuel flow. On my 3 cyl, there are 2 screws and sometimes I have to open both. There is also another bleed screw (also 10mm)on top of the fuel injection pump. You'll need a flashlight to see it. After doing all this in stages, I generally have no more air in the system and the engine runs fine. I do not move the throttle at all unless I'm not getting full RPM's and then have to also bleed at the injectors. Then I open up the throttle and have someone crank the engine. Good Luck
Did you pump and bleed the Racor after putting in the new filter ? If not you still have air in the system. Then when you open up the 10mm screw on the filter and pump manually, you should get air bubbles and good fuel flow. On my 3 cyl, there are 2 screws and sometimes I have to open both. There is also another bleed screw (also 10mm)on top of the fuel injection pump. You'll need a flashlight to see it. After doing all this in stages, I generally have no more air in the system and the engine runs fine. I do not move the throttle at all unless I'm not getting full RPM's and then have to also bleed at the injectors. Then I open up the throttle and have someone crank the engine. Good Luck
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Ken Palmer
My Yanmar will stall
My engine will stall every time if I have not bled all the air out of the line after changing the filter. The symptom is the engine will start, then after a few seconds seem to be starved for fuel and quit. It will not restart until I completely bleed the lines. I think you have a different problem. Not sure what though. Sorry. Ken Palmer, S/V Liberty http://www.LakeOntarioSailing.com
My engine will stall every time if I have not bled all the air out of the line after changing the filter. The symptom is the engine will start, then after a few seconds seem to be starved for fuel and quit. It will not restart until I completely bleed the lines. I think you have a different problem. Not sure what though. Sorry. Ken Palmer, S/V Liberty http://www.LakeOntarioSailing.com
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Bryan C.
Bleeding the Yanmar
3800 seems like high RPMs for a 2GM. My '88 3GM has max RPM rating of 3400 and so cruising RPM at about 75-80% is about 2700. If your engine is running smoothly, doubt it's air. If you had air in the system, I doubt your motor would start at all. Air causes the motor to stall. If you had an intermittant air leak, you would probably see the motor RPMs falling and climbing. Could your lower max RPMs become from other sources? Dirty bottom or prop? Did you properly install the new filters so that fuel flow is being restricted? Possibly a bit of grit is cloggin an injector. Your bleeding problem could be the little lift pump lever. They are not very strong. I have read that on certain engines if crank is aligned in a particular way it will not work. If its old there could be a tear in the internal diaphragm. I followed a tip I got here on the HOW and installed a bulb pump made for OB motors in the line between the primary (racor) filtor and the engine. If pumps fuel far more efficiently than the lift pump and makes bleeding a snap.
3800 seems like high RPMs for a 2GM. My '88 3GM has max RPM rating of 3400 and so cruising RPM at about 75-80% is about 2700. If your engine is running smoothly, doubt it's air. If you had air in the system, I doubt your motor would start at all. Air causes the motor to stall. If you had an intermittant air leak, you would probably see the motor RPMs falling and climbing. Could your lower max RPMs become from other sources? Dirty bottom or prop? Did you properly install the new filters so that fuel flow is being restricted? Possibly a bit of grit is cloggin an injector. Your bleeding problem could be the little lift pump lever. They are not very strong. I have read that on certain engines if crank is aligned in a particular way it will not work. If its old there could be a tear in the internal diaphragm. I followed a tip I got here on the HOW and installed a bulb pump made for OB motors in the line between the primary (racor) filtor and the engine. If pumps fuel far more efficiently than the lift pump and makes bleeding a snap.
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Ed Collins
Tell me More About the Bulb Pump, Bryan
Bryan, The engine starts and runs fine but the RPMs and boat speed seem slow. The manual pump has never produced either bubbles or fuel flow at the bleed screw on the fuel filter. I suspect the diaphragm may be torn. Tell me exactly how to install the bulb between the Racor and the engine. What about the possibility of fuel leaks at the bulb since I guess that the installation involves rubber or poly tubing, not metal tubing. Ed
Bryan, The engine starts and runs fine but the RPMs and boat speed seem slow. The manual pump has never produced either bubbles or fuel flow at the bleed screw on the fuel filter. I suspect the diaphragm may be torn. Tell me exactly how to install the bulb between the Racor and the engine. What about the possibility of fuel leaks at the bulb since I guess that the installation involves rubber or poly tubing, not metal tubing. Ed
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Gordon Torresen
2GM air in fuel lines.
One thing nice about the G series Yanmars, and anything older, you know exactly where you are if you get air in the fuel lines. The engine will not run. Any air is an immediate shut down. When bleeding air from the system, you cannot bleed out the air until after the lift pump, when it is positively pressurized. The ultimate goal is to have air free fuel at the injectors. If air is in the lines between the HP pump and the injectors, it merely compresses and in so doing reduces the pressure below what is required to open the injector valve. To get air free fuel out of the HP pump, you must have air free fuel going into it. The main place to bleed is the 10mm bleed screw that is right on the LP side of the HP pump. We never put fuel into the filter bowls. We change the filter, open the last bleed screw available and operate the fuel lift pump. Sometimes the internal lift pump lever is on the high of its actuating cam so you cannot stroke it. This is overcome by rotating the engine a few degrees so that a full stroke is felt. When clear fuel flows at the bleeded, it is shut down, the injector tube nuts are cracked, the throttle is opened and the engine is cranked until fuel drips from the injector nuts. Tighten the injector nuts and start the engine. If your lift pump diaphragm were ruptured you would be filling the crankcase with diesel fuel. The best check is your dip stick. The pumper bulb in the fuel line is for those who don't understand how things are supposed to work and they introduce a number of additional joints that may become air leaks. The 2GM20 governor shoul be set to limit the max RPM to 3600. This is with a wide open throttle, in neutral (don't do it for long). Your 3800 should not happen. It could be a tach problem or the max RPM limiter could be maladjusted. Your max sustained RPM should be about 2900, or less.
One thing nice about the G series Yanmars, and anything older, you know exactly where you are if you get air in the fuel lines. The engine will not run. Any air is an immediate shut down. When bleeding air from the system, you cannot bleed out the air until after the lift pump, when it is positively pressurized. The ultimate goal is to have air free fuel at the injectors. If air is in the lines between the HP pump and the injectors, it merely compresses and in so doing reduces the pressure below what is required to open the injector valve. To get air free fuel out of the HP pump, you must have air free fuel going into it. The main place to bleed is the 10mm bleed screw that is right on the LP side of the HP pump. We never put fuel into the filter bowls. We change the filter, open the last bleed screw available and operate the fuel lift pump. Sometimes the internal lift pump lever is on the high of its actuating cam so you cannot stroke it. This is overcome by rotating the engine a few degrees so that a full stroke is felt. When clear fuel flows at the bleeded, it is shut down, the injector tube nuts are cracked, the throttle is opened and the engine is cranked until fuel drips from the injector nuts. Tighten the injector nuts and start the engine. If your lift pump diaphragm were ruptured you would be filling the crankcase with diesel fuel. The best check is your dip stick. The pumper bulb in the fuel line is for those who don't understand how things are supposed to work and they introduce a number of additional joints that may become air leaks. The 2GM20 governor shoul be set to limit the max RPM to 3600. This is with a wide open throttle, in neutral (don't do it for long). Your 3800 should not happen. It could be a tach problem or the max RPM limiter could be maladjusted. Your max sustained RPM should be about 2900, or less.
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Bryan C.
Bulb pumps
I'm one of those who doesn't know how things are supposed to work, but lots of folks have installed a bulb pump in their fuel and liked it. Like I said, I got the idea from someone here on the HOW. Then again, Gordon's the expert and knows a lot more about diesels than I do. However, a bulb pump is very effective and a few pumps on the bulb sends fuel squirting out of the bleed points. I don't have to worry about how the engine is rotated nor crank the engine while bleeding. I don't fill the bowls either when I have changed them; with the bulb pump it only takes a few squeezes to pull fuel into the bowls (with the bleed screw on the secondary (engine mounted) filter open). Then you don't have to screw around pumping your finger off on the little lift pump. I have read that over a few years the bulbs can collapse, so spend an extra $5.95 and get a spare. I put the bulb pump (bought at any marine store) in the rubber hose between the primary (i.e. Racor) filter and the engine (where the hose connects at the lift pump). I just cut the rubber line and installed the bulb pump with a couple hose clamps. The trick is getting the correct size bulb pump, on my engine it was the thinner of the two standard sized bulb pumps, but don't remember offhand what size the line was. Gordon can probably tell us the fuel line size on a 2GM. Leave yourself enough hose on the engine side so that if you ever needed to bypass the bulb pump you would have enough hose to hook it back directly to the primary filter. (Another advantage is that if you have a problem with a clogged primary filter in an emergency you could by bypass it more easily by connecting the line straight from the tank to the bulb pump -- of course don't do this unless it's an emergency because then you only have the secondary filter to keep crud out of your engine). Some folks have reported that they put the bulb pump in the line between the fuel tank and the primary filter and say it works fine that way, too. Bleeding with the bulb pump has been a snap. It's much more efficient than than the lift pump, IMHO.
I'm one of those who doesn't know how things are supposed to work, but lots of folks have installed a bulb pump in their fuel and liked it. Like I said, I got the idea from someone here on the HOW. Then again, Gordon's the expert and knows a lot more about diesels than I do. However, a bulb pump is very effective and a few pumps on the bulb sends fuel squirting out of the bleed points. I don't have to worry about how the engine is rotated nor crank the engine while bleeding. I don't fill the bowls either when I have changed them; with the bulb pump it only takes a few squeezes to pull fuel into the bowls (with the bleed screw on the secondary (engine mounted) filter open). Then you don't have to screw around pumping your finger off on the little lift pump. I have read that over a few years the bulbs can collapse, so spend an extra $5.95 and get a spare. I put the bulb pump (bought at any marine store) in the rubber hose between the primary (i.e. Racor) filter and the engine (where the hose connects at the lift pump). I just cut the rubber line and installed the bulb pump with a couple hose clamps. The trick is getting the correct size bulb pump, on my engine it was the thinner of the two standard sized bulb pumps, but don't remember offhand what size the line was. Gordon can probably tell us the fuel line size on a 2GM. Leave yourself enough hose on the engine side so that if you ever needed to bypass the bulb pump you would have enough hose to hook it back directly to the primary filter. (Another advantage is that if you have a problem with a clogged primary filter in an emergency you could by bypass it more easily by connecting the line straight from the tank to the bulb pump -- of course don't do this unless it's an emergency because then you only have the secondary filter to keep crud out of your engine). Some folks have reported that they put the bulb pump in the line between the fuel tank and the primary filter and say it works fine that way, too. Bleeding with the bulb pump has been a snap. It's much more efficient than than the lift pump, IMHO.
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Ed Collins
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Bryan C.
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