There are two pumps in the systems, a "lift pump", also known as a "low pressure" pump, and an "injector pump", also known as a high pressure pump.
The lift pump is the one with the lever on it. The purpose of the lift pump is to pull fuel from your fuel tank through the Racors (known as primary fuel filters) and then push it through the 2ndary fuel filter (the one on the engine) and to the injector pump.
The injector pump's job is to delivery a pressurized feed of fuel to each cylinder's fuel injector, such that the injector has enough pressure to get a good spray into the cylinder. It actually delivers more fuel than is needed. The remaining fuel comes back out of the injector and returns to the tank.
You've found the lifter pump. The injector pump is the one that has the four (4) lines coming out of it and running to each injector. If you look at each injector, you'll see it has a larger line going to it, and a smaller line connecting them all together. The common one is the return.
To start out with, make sure there is no air in the Racor. You likely will need to loosen the top to check. Fill it as close to full as needed. If your fuel level is above the Racor and there is no check valve, simply loosening the top may let the air out and let it fill. In any case, get it as full as you can, because the more full it is, the less air you need to bleed. Get ready with absorbent rags to clean up any mess.
Next go to your fuel filter. On top, there is most likely what is called a "banjo bolt". It looks like a bolt from the top, but inside there is a hole drilled through it that fuel can pass through. You'll note that the fitting around it has a fuel line coming off. Loosen this screw, cover it with absorbent rags, and operate the fuel lifter pump until fuel comes out or the handle gets firm when pumping. The tighten up that bolt. Some engines might have a version that doesn't have the banjo bolt at the top and has an actual bleed screw, but I don't remember those details and I think that is a rare version of the pump.
Next move on to the injector pump. There were a few different injector pumps used in those engines. One was self-bleeding, but I think it was only used in tractors. For the ones installed in boats, there was a "mechanically governed" pump and a "hydraulically governed pump". The hydraulic version is a bit more responsive, but some say it is also more finicky. I think most in engines are hydraulic and most in generators are mechanical. But, don't hold me that. It is an impression based upon a very small sample.
In any case, if you have the hydraulic pump ("DPA style"), you'll see a small panel cover, likely secured by a wire. Directly above that you'll see a screw with a spring around it. That is the idle adjustment. And, directly above that, you'll find a small hex head screw (/not/ a cap screw, something you can put a small wrench on). That is one of the two bleed screws on the pump. If you find the throttle arm, the lever that is controlled by your throttle cable, and find the screw it pivots on, directly above that you'll find another hex head screw, like the first one. It is the second of the bleed screws on the pump.
If you've got a mechanically governed pump ("DPS style"), there is only one bleed screw. If you find the throttle lever, the bleed screw is a hex-head screw as described above -- but below the end of the throttle arm (not the pivot point, but just below and a little bit in from the distal end).
To bleed the pump, loosen the bleed screw(s) (I can usually get away with just loosening the lower one on the pumps with two, but that isn't the recommended practice) until it is good and loose, but not all the way out, cover all around, under, and over that screw with absorbent cloth, and start pumping with that lifter pump handle. Keep pumping until you get a firm feel on the lever when pumping, fuel gushing out of the bleed screw -- without foam or bubbles or other signs of air. Then tighten the screw(s) back up.
If the pumping is easy and nothing is happening, you are moving air. Keep going. It can take a couple hundred pumps or more sometimes. This is why many peel install electrical bleed pumps.
At that point, you can probably get the engine to bleed itself with just a little patience. But, that isn't the recommended practice. The recommended practice is to also bleed the injectors. To do this, follow the fuel lines from the injector pump to the injectors. Pick one or two. Loosen the but around the fuel line at the injectors and cover the areas with absorbent rags. Pumping with the lifter pump won't help you here. You've more-or-less got to bump the starter until the fuel coming out is gushing out, and free of bubbles and foam. Then, tighten up. I can usually get the engine to start without doing this step, but when I do, I bleed the highest injector and maybe some other. Try not to start the engine while bleeding. But, if it starts, that is okay. Just tighten up the injectors. Air in the return lines will bleed itself.
Do heed the advice given earlier by others: Cranking an engine that doesn't start can pump water into it. Since water doesn't compress like air, it can bend and break things if the engine gets turned over in that state. If you have to turn the engine over a lot, keep the seacock closed until it is running and then quickly open it. If you think you might have done that, get getting it out. You'll end up needing to check in the exhaust, and possibly removing the injectors and turning the engine over by hand, etc. How likely this is to occur totally depends upon the details of how the engine is installed.
I hope this helps.
-Greg
