S2 8.0, Yanmar 1cyl won't start

[ChockFullOnuts222]

The boat in question is my father's boat, a 1982 or 83 S2 8.0 with a 1 cylinder Yanmar diesel engine. The engine will not start...starter cranks, but the engine does not try to fire.

Background:

We took the boat out for the 4th of July. The boat stalled multiple times on our way from the marina to the beach where our destination was. We would be running along fine, engine running well, and then the RPM's would suddenly stumble and decrease as if we had just run out of fuel. Each time this happened, the engine restarted--although not always easily. This occurred maybe 6 or 7 times within 20 minutes or so, and then never happened again for the rest of the night. Our return trip to the marina was without incident, and the engine ran normally.

The next day, my father went out to the boat, and the engine wouldn't start. He said that it tried to fire a couple of times, and then that was it. Ever since then, the starter turns the engine over but cannot get the engine to fire.

- We have bled out the fuel system half a dozen times by now. Air in the system seems to be a non-issue.
- Exhaust is not clogged
- Air intake is not clogged
- water pump is pumping
- Fuel is reaching the injector
- Fuel Injector is new
- A new fuel injector high pressure pump has been installed by a marina mechanic (although he is self-admittedly not a Yanmar specialist).

Can anyone help me with some troubleshooting tips? The manual that came with the boat is useless. My father has read somewhere that the mounting of the high pressure fuel pump is critical in relation to some sort of timing in the engine, and that a professional needs to properly adjust it to work correctly. If this is true, do any of you guys know that procedure?

Also, is there a way to check the compression in this diesel engine to be sure that the valves are not damaged? Is there a pipe plug port where a compression guage can be installed to the cylinder?

The whole problem has us stumped...it's getting fuel to the injector, has a new high pressure pump and injector, and won't even hint at trying to start.

Thanks for any help you can offer!

 

[RussB]

I was able to find a pdf file online of the entire service manual for my Yanmar 2qm15. It has very good detail about maintaining the fuel system. There should be a pdf service manual for yours out there as well.

I was told that if I ever removed the injector pump that I needed to mark its shim locations precisely to preserve the timing of the pump.

 

[Jim11240]

Engines do not start for one of three reasons: 1. No fuel 2. No compression 3. No air

Fuel has to get all the way to teh injector and into the cylinder. You may have dirt in the fuel and now you may have a plugged injector. Pull the injector out and see if it sprays when you turn the crank. Be carefull the injector pressure is very high and will inject diesel right through your skin if you hold it close enough,

No Compression - try turning the engine with the hand crank, Do you feel strong resistance on the compression stroke? if not you may have a leaking valve or a blown head gasket. Valves can leak because your compression release is holding them open, they are adjusted incrrectly, they are broken or some part of the drive train is broken,

No Air: Try removing the air cleaner, inspecting the airpath for any obstrucitons ( animal nest? rag? clogged filter?) removing them, and cranking the engine.

Jim

 

[BobT]

I have a 1 cyl Yanmar (1GM10). And it behaves similarly when starved for fuel. There is a large separating bowl type of filter mounted near the tank, and a small element-in-a- bowl type mounted on the engine (starboard side). Both should be replaced if there is a starting issue. On top of the engine filter housing is a bleed screw. It looks like a hex head bolt with a phillips in the center. Back it open a turn and find the finger lever on the back of the fuel pump. Stroke the pump lever until it squirts fuel without air bubbles, and tighten the bleed screw. Repeat for the bleed screw on the front of the engine above the starting crank pin. This has worked for me a couple of times now.

 

[BobM]

Many people think they are doing a good thing when they replace their fuel filter with a 2 micron instead of a 30 micron, which is what Yanmar often recommends. If your fuel tank is nigh empty and hasn't been cleaned out lately you may just be sucking up crap.

You should also check the exhaust mixing elbow, which has a limited lifespan on 5-10 years and often goes unserviced. Another indication of this is if the engine had been generating a lot of soot and was failing to achieve max recommended RPM. It may be pretty clogged up. Be warned though, removing the elbow is a pain. Hose it down with PB blaster (be careful as it removes paint too) a few days in row before trying to break it loose.

It is often clogged by broken blades from the water pump impeller so the first step is to examine that.

 

[ChockFullOnuts222]

Thanks for the suggestion about the exhaust mixing elbow; we'll have to check that out this weekend. My dad pulled the cylinder head off the engine last weekend to check the valves, too. I wasn't there when he did it, though; so I don't know what the head gasket looked like when it came off.

As far as filters....both fuel filters were replaced with new ones, and the fuel system was bled out. Air intake and filter looked good, with no obstructions. Fuel tank was almost full.

Is it possible to have had a blockage in the exhaust (at the mixing elbow, for example), that caused the head gasket to blow out and leak compression in the cylinder?