01-10-2022, 01:06 PM
At this point, the temptation was to button it back up. But………
I bought, $100 who knew?, a test stand for checking the injectors. It applies high pressure diesel to the injector so you can see the spray pattern, measure the “pop” pressure, and see if the internals are leaking. All important things to a clean burning engine. I did make some minor adjustments to the pop pressure to ensure it was in Yanmar spec, 2800 psi. By the way don’t put body parts next to the injector while doing the test or you will inject diesel under your skin. Not a good idea.
Ok the injectors are good. But…….. the head is off, and although the cross hatching in the cylinder walls looks pretty good, I decide to pull the pistons. After all, rings not sealing correctly can also be the cause of the low compression. I did run a quick and dirty compression test again after lapping the valves but before pulling the pistons. I got about 320 psi, better than before, but not the 350 spec in the manual. I did the classic test for leaking rings by squirting oil in the cylinder and retesting. That brought the pressure up to 350. So I decided to pull the pistons, rehone the cylinder, and install new rings.
For grins, here are two pics of the cross hatch in the cylinder. The first is the as found after 6000 hours on the motor. The second is after I rehoned the cylinder.
The red tape was to prevent honing debris from entering the oil and coolant passages in the block.
The next step was the scary one for me, and ended up creating a small problem which I will detail later. To remove the honing debris, the instructions are to scrub vigorously with Dawn and hot water. Since I did this work as an in frame, the crank is still in place. I did as best I could to protect the crank and clean the journals before reassembly. But pouring hot water into an engine makes me queasy.
All right, button it all back up. Compression is 350, but with brand new rings and cross hatching, with no time to develop a good seal. A quick squirt of oil into the cylinder brings the compression up to 400, so happy dance all around. Put the injectors in as a final step, bleed the fuel system, and it fires on third try. Woo Hoo. And NO SMOKE. After a few minutes, start loading the generator with Aquahot and water pump, and stove, and dryer till we get to over 40 amps on each leg. Still no smoke. Woo Hoo.
I bought, $100 who knew?, a test stand for checking the injectors. It applies high pressure diesel to the injector so you can see the spray pattern, measure the “pop” pressure, and see if the internals are leaking. All important things to a clean burning engine. I did make some minor adjustments to the pop pressure to ensure it was in Yanmar spec, 2800 psi. By the way don’t put body parts next to the injector while doing the test or you will inject diesel under your skin. Not a good idea.
Ok the injectors are good. But…….. the head is off, and although the cross hatching in the cylinder walls looks pretty good, I decide to pull the pistons. After all, rings not sealing correctly can also be the cause of the low compression. I did run a quick and dirty compression test again after lapping the valves but before pulling the pistons. I got about 320 psi, better than before, but not the 350 spec in the manual. I did the classic test for leaking rings by squirting oil in the cylinder and retesting. That brought the pressure up to 350. So I decided to pull the pistons, rehone the cylinder, and install new rings.
For grins, here are two pics of the cross hatch in the cylinder. The first is the as found after 6000 hours on the motor. The second is after I rehoned the cylinder.
The red tape was to prevent honing debris from entering the oil and coolant passages in the block.
The next step was the scary one for me, and ended up creating a small problem which I will detail later. To remove the honing debris, the instructions are to scrub vigorously with Dawn and hot water. Since I did this work as an in frame, the crank is still in place. I did as best I could to protect the crank and clean the journals before reassembly. But pouring hot water into an engine makes me queasy.
All right, button it all back up. Compression is 350, but with brand new rings and cross hatching, with no time to develop a good seal. A quick squirt of oil into the cylinder brings the compression up to 400, so happy dance all around. Put the injectors in as a final step, bleed the fuel system, and it fires on third try. Woo Hoo. And NO SMOKE. After a few minutes, start loading the generator with Aquahot and water pump, and stove, and dryer till we get to over 40 amps on each leg. Still no smoke. Woo Hoo.
Richard and Rhonda Entrekin
99 Newell, 512
Maverick Hybrid Toad
Inverness, FL (when we're home
)