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January 30, 2009


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I am a little confused by your question. It sounds like you have disconnected some pipes from the filter housing. At no time do these need to be unscrewed. Assuming that you have the Racor filter unscrew the T bar, lift off the lid, remove the old filter element. Then replace with new element, O rind in cover and O ring on T bolt which come with the filter. This does introduce air into the system but unscrewing the nut on the injector pump half a turn and operating the lift pump will purge air from the fuel lines. Keep pumping until a steady stream of fuel with no bubbles comes out then tighten the nut. Remember that the primary filter is on the suction side of the pump so if any of the connections are loose you will be sucking air in and not pulling fuel from the tank. I am not sure what you are on about with the bucket of fuel. The glass bowl does not need to be removed.

Thank you for these clear instructions and photos: I had to bleed a 2GM20 which is, of course, very similar. Mission accomplished!

But I have a question: how long should one expect to pump with the manual lever?

With a pipe-run from the primary filter of about 1.2 metres and a vertical rise of about 25cm, we pumped with the manual lever for about an hour without seeing any result. During this time, we spun the engine a few times, to ensure that it hadnt stopped with the lift-pump in the inoperative position.

We got bored with manual pumping, and used the starter motor to turn the engine and operate the lift-pump. (We disconnected the raw-water pump, so as not to drown the engine, and gave the starter motor pauses to cool.) This quickly brought diesel to the first bleed point.

The pipe run from the first bleed point to the second is about 20 cm, running downwards. We were expecting 'a couple of strokes' of the manual lever to be sufficient. But after several minutes of manual pumping, we got bored, and used the starter motor again. This quickly brought results.

It seems unlikely that the lift-pump was caught in the inoperative position EVERY time we spun the engine. So my question is, might there be some other reason for the manual lever not to work? Or did we do all the hard work with the manual lever, and the starter motor just finished the job? I expected to have to pump manually for a while to clear a lot of air from the first pipe-run, but an hour?

Yanmar advise that bleeding the high pressure side (after the fuel injection pump) is usually not required, the pressure will blast through any air. And so it was, after bleeding the two points on the low pressure side, the engine started without problems.

So thank you again, but can you give a ball-park idea of how long one should expect to pump manually?


Thanks for the comment. How long you have to pump depends on a lot of factors, especially the length of pipe run from the tank to the pump. you should not have to pump for the amount of time that you did. As you say the pump may have been in the wrong position or you could have been sucking air. If there is the slightest leak on the suction side then air will find its way in. It's hard to say without seeing the installation. As you found out it's OK to crank the engine but you must shut off the raw water to avoid filling the exhaust with water and disconnect the pump - the easiest way to do this on the small Yanmars is just to loosen the pump belt so it will not turn. Once then engine fires shut it down right away and retighten the water pump belt and all will be well. The short answer to your question is normally 5 minutes should be all that is required. Things can be speeded up somewhat by pre filling the fuel filter be refitting if this has been changed.

Mark: I have a 40 yr old Yanmar YSE8 in my boat. The manual is not much help, as the pictures are not detailed and without labels except for the main components. Not being at all familiar w diesels, I can't tell if there is a bleeder screw on the fuel lift pump or on the injector pump. (I was successful, however, in rounding off the knuckles on the fuel line trying to loosen the compression fittings...) If you know about the bleed screws, pls let me know. Many thanks, Ed


Thanks for the comment. Your engine is basically the early iteration prior to the very popular 1GM series engine except the cylinder is laid to the side. There were different versions of the engine that you have, either with a hand crank or without. Bleeding any engine it's best to think about how the fuel system works, then once you understand this you should be able to bleed air from most any engine, including yours. Essentially there are three distinct different 'zones', for want of a better word. These are the suction side which comprises of the hose or pipe coming from the tank to the fuel lift pump. Next is the pressure side which is all the pipe work from the out feed on the lift pump through the injector pump then to the injector itself. Finally, because the pump moves more fuel than the motor uses there is a fuel return pipe from the injector pump back to the tank. Often the majority of fuel problems are on the suction side between the tank and the lift pump as an air leak here will suck air into the system whereas a leak between the pump and injector will show up as leaking fuel as this is on the pressure side. Incidentally a leak here will not necessarily prevent an engine from running. The same is also true of the return pipe and this can almost be discounted as this merely returns unused fuel to the tank and is almost never a problem.
Having said all that air in the system causing hard starting is fairly easy to purge. In your case loosen the pipe coming from the lift pump that goes to the injector pump. Half a turn only. Crank the engine either by hand or with the starter, but turn off the seacock to avoid sucking in seawater and back filling the cylinder through the exhaust valve. Open the decompressor to allow the engine to turn over easily. Turn the engine until fuel bubbles from the loosened union mentioned above. Stop cranking and retighten the loosened union. Next loosen the pipe to the injector and repeat the procedure. When fuel comes out retighten, shut the decompression lever and the engine should start. Open the seacock.

Your opening picture appears to show you cranking the engine while lifting the lever at the top of the motor. What is this proceedure for? I didnt see it mentioned in the article.

This shows the operator cranking the engine while opening the decompressor. Only small engines tend to have a decompressor and while this is a useful method for cranking the engine to operate the lift pump you don't have to do this. In short this is simply an opening picture to show the complete engine.

to Jim Hatch;
if possible pre fill the new fuel filter between the tank and the fuel lift pump.
ONE thing not mentioned here is : when using the small lever on fuel pump sometimes the fuel pump internal cam lever is on the full lift of the cam shaft and the manual lever will be unable to operate the internal diaphragm as it is in the full stroke position. Simply decompress and rotate the engine one revolution by hand, this rotates the camshaft and allows the hand lever to operate the internal diaphragm the full stroke. the first point of bleeding as originally mentioned by Mark is the engine mounted filter bleed screw, once that has bleed all air, the next bleed point will be the injector pump bleed screw. From injector pump to the actual injector, it cannot be bled by the fuel feed pump lever. From the injector pump to the injector head itself, is extremely high pressure and can only be produced by engine rotation. Just crack open the gland nut on the delivery pipe to the injector, hand crank engine with decompression lever engaged (to save battery)until just fuel squirts from the gland nut without any foam. Tighten gland nut...engine should start...
Hope this also helps..coming from a very experienced marine and diesel specialist.
cheers from St Kilda , Australia

Hi Mark,
I have a 33hp Westerbeke. It used to run fine. I installed a new raw water pump and primed it by filling the hose to the heat exchanger up with water and also the hose that goes from the water filter to the intake port of the pump. Engine won't fire up now. It seems to be laboring when turning over
Any thoughts?


Not sure what's going on there except to say that the pump should self prime. The only thing I can think of is that you've over filled the hoses and back filled the cylinders with water causing a partial hydraulic lock.

Mark, thanks for the great tutorial. I came across your advice a little too late. I'm worried Ithat I've already filled the exhaust with water. I changed both fuel filters and did not fill the new ones with fuel before installing. I tried to fill the new filters by turning over the engine. I never held it for more than 10 secs but I must have tried upwards to 30 times. And I did not turn off the raw water. The engine does not turn over every time I try, sometimes there's just a "click".

Have I already hydrolocked my engine? If so, how do I get the water out? Will it evaporate if given enough time?

Also, when trying to bleed the lines, I can't get fuel to come out of any of the bleeder screws. I am guessing there's air getting in somewhere. I did tighten down the nut on the top of the primary fuel filter because it wasn't all the way tight but I am pretty sure it was air tight. Haven't tried again since because I also checked the fuel lines and spilled fuel all over the engine so I wanted to let it sit overnight to evaporate. It seems like I'm getting fuel to the primary filter but not beyond. Hopefully tightening that screw on the top fixed that but I'm doubtful.

Thanks again for your advice!

Mark, I have a Yanmar 2GMF with new fuel lines from the tank, new Racor 120 Primary filter, new lift pump, new secondary filter. I can bleed the secondary filter and the injection pump. I did not bleed the injectors. The engine starts and runs for 2-3 minutes, then stops. It seem the engine depletes the fuel in the secondary filter bowl then stops. Any ideas are appreciated!

This a fuel problem and sounds like fuel starvation. The engine will pull far more fuel than it uses, surplus fuel is returned to the tank. Check the hoses before the fuel filter to make sure there's no obstruction. It could also be that the primary fuel filter is clogged - when was it last changed?
It could be the fuel pump but you say that this has been replaced so I doubt it's this. Double check the hoses on the delivery side and the filter I bet something is clogged.


It is possible that the engine is hydraulically locked. So don't try to crank it or you will do some damage. To check if the exhaust is full of water undo the pipe clamps where the flexible pipe meets the riser. If this is full of water then it is almost certain that the cylinders will be full of water. The water will not evaporate and as it is salt water it is very corrosive so you need to get it out of the engine ASAP. You'll need to remove the injectors then crank the engine over with the water off to force the water out.

Mark, thank you. I actually got it running after manually filling the fuel filter and lines. But now it seems like I have a runaway engine! Scary! It shut down after I thought it was going to explode. Going to check the oil since I just changed it but I'm positive it was right at the max fill line. I'm guessing it will be higher when I check and that I'm getting fuel in there somehow. Always something!

Do you have to unscrew the filter body to replace the element?

There should be two fuel filters. The small one as shown in the photos and a primary filter, often a Racor or something similar, between the tank and the motor. I'm assuming that you are talking about the filter on the engine, and yes you do have to unscrew the bowl to replace the filter element. This is explained in the owners manual for your particular engine. It is also worth noting that the filters should be changed each year even if the motor has not been used a great deal.

Great article, thanks. When i operate my lift pump fuel does not come out of the bleed screw. Can you help? The primary and secondary filters are full of fuel, there is no obvious blockage between the primary filter and the lift pump, the tank is full of fuel. Any ideas? Thanks


The lift pump may be stopped in the wrong position. Turn the engine over a quarter turn with a socket and bar on the end of the crankshaft nut and this should fix it. If that is not it then I would suspect an air leak in the line between the secondary filter and lift pump.


How long may fuel be stored in a fuel tank in a boat which has been in dry dock storage for the last five years? The fuel tank is not metal.



If the fuel is five years old it will at least need polishing. I'm assuming that this is diesel but you don't say. If it's gas then it will not be any good now as it will have what's known as phase separated and will need to be disposed of. If it's diesel i would suspect some algae in the tank and this will clog filters and injectors if you are not careful. Talk to a diesel mechanic in your area and get a price for getting the fuel polished, it could save you a lot of heartache in the long run. If it's just a few gallons then it may be best to just dispose of the fuel properly and refill the tank with fresh fuel. In any event replace all the fuel filters.

Hello, I'm new to the world of sailing and have only had my sailboat for about a year. I'm pretty handy with spanners and a hammer so I thought I would tackle my own engine service this year on my Yanmar 1GM 10. All went smoothly, or so I thought. I'm now having this stupid issue. I bled the engine as advised and she fired up first push of the button. I ran the motor with full throttle in neutral for about 10 minutes to make sure all was good. I launched the boat and started to motor up to the river, I noticed she started to die so I sailed her to a buoy and realized there was a little air in the system, I bled her again and off we went. Five minutes later it happened again... this happened almost every time she is under load.. can anyone advise what is going on or where i should start looking to fix this issue.

This sounds like air in the system for sure, so make sure that all hose connections of the suction side are tight. If the motor runs but dies under load it could also be that there is too much load on the prop. Is the propeller the right size? Is there some resriction on the shaft that is putting the engine under stress? I'm also a little concerned that you ran the engine at full throttle in neutral. This is not good for the engine, when warming the engine a max of 750 rpm is more than enough. Also it sounds as though you ran the engine out of the water. Did you have it connected to water to provide cooling?


Excellent narrative and photos. Recently bought boat with 1GM (1983 boat, no known history of overhaul). It actually looks almost as good as your demo. Surveyor said it ran well, but I had never run it. It had 3 fuel leaks; at old primary filter with opaque bowl, at lift pump, and at engine mounted filter outlet banjo. Fuel out, air in, so when it went in the water, it wouldn't start, despite leak stoppages. Had already decided on Racor 500 filter, so also did new hose, all new banjo washers, new engine-mounted filter, and air filter. Rebuild kits for lift pump no longer available, so will later buy new pump. Bleeding was normal, as you describe, but finger pump moved very little fuel so took long time. Perhaps travel was limited by cam position, as one of your reader implies. Will try finger pump in several crank positions to test. Of course, it runs! Appreciate your suggestion to color code bleed points.

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