Buenos Nachos, I am in the process of trying to bleed my diesel fuel lines. Things are not going as well as I had hoped. I am hopeful that someone may clear up my understanding of what to expect when doing this. I replaced the fuel lines and since I only had a vague idea of how to bleed the new lines I visited this sites archives articles on bleeding diesel fuel systems. I guess I am still wondering, how difficult of a process is this? I seem to still have air in the lines after a lot of trying to get it out. How long can I safely crank the starter without burning it out? I have been cranking 15 secs while bleeding (with raw water intake thru hull closed). Then I let the starter cool a few minutes before trying again. I made sure the Racor is full, then bleed at the second filter, then made sure Racor is topped off before cranking again. The Racor seems to be staying full now and I don't have bubbles at first bleed point by second filter. Then I tried to bleed from input to injection pump. A lot of bubbles came out even after repeated attempts to bleed that point. Just keep bleeding, don't be a quitter??? Tips? Pointers? Recommendations? Thanks to all, Arturo.
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Hand pump first
Before cranking endlessly (and yes you can burn out the starter and drain your batteries but probably not in 20 seconds); use the hand pump. Look for a lever on the side of the engine. Follow lines from the RAcor upline and you see a small diaphram type pump on the engine (usually starboard side). Pressure up with that first. To completely exhaust the air (although a bit messy), you can let a 2 cylinder run on one cylinder why bleeding the second cylinder at the injection line.
Before cranking endlessly (and yes you can burn out the starter and drain your batteries but probably not in 20 seconds); use the hand pump. Look for a lever on the side of the engine. Follow lines from the RAcor upline and you see a small diaphram type pump on the engine (usually starboard side). Pressure up with that first. To completely exhaust the air (although a bit messy), you can let a 2 cylinder run on one cylinder why bleeding the second cylinder at the injection line.
Bleeding steps
Andy, Thanks very much for your kind response. Here is the thing. My diesel is ancient but usually very reliable. It's an old YSB12, Yanmar. It a single cylinder, and alas, does not have a handpump on the side of the engine. No lever, no handpump. The Racor itself does not have a built in pump as some do. The fuel line travels from Racor to an electric pump on the side of the Yanmar. Thanks for the points you made. I appreciate it. Regards, Arturo.
Andy, Thanks very much for your kind response. Here is the thing. My diesel is ancient but usually very reliable. It's an old YSB12, Yanmar. It a single cylinder, and alas, does not have a handpump on the side of the engine. No lever, no handpump. The Racor itself does not have a built in pump as some do. The fuel line travels from Racor to an electric pump on the side of the Yanmar. Thanks for the points you made. I appreciate it. Regards, Arturo.
Bleeding...
the lines with no pump on the engine can still be done. Back in my mechanic days some of the older detroit diesels did not have hand pumps. They make a pump that you can screw onto the fuel line and then put the hose in a bucket or tank of fuel and then prime it. One more step but it works. I had to do this one time when a driver ran out of fuel along the freeway and he was driving a tanker hauling diesel. Rob
the lines with no pump on the engine can still be done. Back in my mechanic days some of the older detroit diesels did not have hand pumps. They make a pump that you can screw onto the fuel line and then put the hose in a bucket or tank of fuel and then prime it. One more step but it works. I had to do this one time when a driver ran out of fuel along the freeway and he was driving a tanker hauling diesel. Rob
Here's a Tip...
...that many people forget. The reason that the engine may not start is that the "Stop" lever is engaged. This cuts off the fuel to the injectors and the engine won't even attempt to start. Make sure it is pushed back to the "running" position once it has been pulled. Once started, and you have bled the fuel filters, bleed the fuel injection pump by loosening the bleed screw. Then bleed one cylinder at a time at the injector by loosening the fuel line bolt at the injector. The cylinder will shutter and shut down as you loosen the nut, but it will quickly bleed - then re-tighten it.
...that many people forget. The reason that the engine may not start is that the "Stop" lever is engaged. This cuts off the fuel to the injectors and the engine won't even attempt to start. Make sure it is pushed back to the "running" position once it has been pulled. Once started, and you have bled the fuel filters, bleed the fuel injection pump by loosening the bleed screw. Then bleed one cylinder at a time at the injector by loosening the fuel line bolt at the injector. The cylinder will shutter and shut down as you loosen the nut, but it will quickly bleed - then re-tighten it.
primeing bulb
like they use on outboards and place it between primary filter and secondary filter. quick way to prime engine
like they use on outboards and place it between primary filter and secondary filter. quick way to prime engine
Electric Fuel Pump
Arturo, If you have an electric fuel pump, that should be able to push the fuel and air out of the lines. I assume that you turn on the key to activate the electric pump. Turn the key on, open the bleed valves until fuel escapes then go to the next bleed point and continue until you are at the injector pump. That pump can push the air out of the system to the injectors. Bill
Arturo, If you have an electric fuel pump, that should be able to push the fuel and air out of the lines. I assume that you turn on the key to activate the electric pump. Turn the key on, open the bleed valves until fuel escapes then go to the next bleed point and continue until you are at the injector pump. That pump can push the air out of the system to the injectors. Bill
Use the decompression lever
Your electric pump should allow you to bleed the system up to the bleeding bolt on the inlet side of the injector pump without cranking the engine at all. Once you get clear fuel ( no bubbles ) at the injection pump, then you will have to crank the engine to get fuel to the injector. Use the decompression lever : it will let the starter spin the engine faster and with much less load on starter or battery. Make sure the throttle is open at least half way. If the throttle is closed the injection pump won't move any fuel as that is how the engine is shut down. Once you start getting clear fuel out of the line going into the injector, close it and bleed the fuel return line too.
Your electric pump should allow you to bleed the system up to the bleeding bolt on the inlet side of the injector pump without cranking the engine at all. Once you get clear fuel ( no bubbles ) at the injection pump, then you will have to crank the engine to get fuel to the injector. Use the decompression lever : it will let the starter spin the engine faster and with much less load on starter or battery. Make sure the throttle is open at least half way. If the throttle is closed the injection pump won't move any fuel as that is how the engine is shut down. Once you start getting clear fuel out of the line going into the injector, close it and bleed the fuel return line too.
Thanks !! Rob, Paul, Gary, Bill and TT.
Thanks for the great input. I am still working on the problem. I added a priming bulb today ( I didn't know if electric pump would work to bleed the lines)I seem to be getting clear fule to the input of the injection pump but nothing comes out of it when I loosen the output valve of the injection pump. Not when I use the electric pump or the bulb. But I feel the fuel is air free to that point. One thing, Gary, I added the bulb to after the Racor and before the electric pump. My thinking was it would draw fuel from the tank, through the Racor, topping the Racor off. Is this a problem? Anyone know the symptoms of an injection pump in need of a rebuild? Thanks again guys, it's very decent of you to help. Regards, Arturo.
Thanks for the great input. I am still working on the problem. I added a priming bulb today ( I didn't know if electric pump would work to bleed the lines)I seem to be getting clear fule to the input of the injection pump but nothing comes out of it when I loosen the output valve of the injection pump. Not when I use the electric pump or the bulb. But I feel the fuel is air free to that point. One thing, Gary, I added the bulb to after the Racor and before the electric pump. My thinking was it would draw fuel from the tank, through the Racor, topping the Racor off. Is this a problem? Anyone know the symptoms of an injection pump in need of a rebuild? Thanks again guys, it's very decent of you to help. Regards, Arturo.
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