Yanmar 2GM Won't Fire - Troubleshooting

[Evan Burkosky]

Wow Sam, what a great writeup, thank you very much! That will be very helpful as I go through this process of diagnosing the issue, and I'm sure others will find this helpful too.

[boatbod]

I strongly suggest you do not use any ether as it can cause detonation and a bent rod. A better bet is to hear the intake air using a heat gun and perhaps a whiff of wd40.

[svsputnik]

Originally Posted by boatbod

I strongly suggest you do not use any ether as it can cause detonation and a bent rod. A better bet is to hear the intake air using a heat gun and perhaps a whiff of wd40.

I would second that. Before getting my hand on a compression testing kit, I talked a bit with a certified Yanmar mechanic that told me exactly that. His take was that the safest way to help it start was to basically "create the same effect as a glowplug" by sending hot air for 20 secs in the air intake with a heatgun. He said that if the fuel is reasonably clean and the fuel line has been bled correctly and that the hot air doesn't allow it to start, then it's 99% sure it's the compression that ain't good. And no amount of explosive that you send inside can help it. "You may get it starting, but that won't fix anything"

[Evan Burkosky]

Originally Posted by svsputnik

I would second that. Before getting my hand on a compression testing kit, I talked a bit with a certified Yanmar mechanic that told me exactly that. His take was that the safest way to help it start was to basically "create the same effect as a glowplug" by sending hot air for 20 secs in the air intake with a heatgun. He said that if the fuel is reasonably clean and the fuel line has been bled correctly and that the hot air doesn't allow it to start, then it's 99% sure it's the compression that ain't good. And no amount of explosive that you send inside can help it. "You may get it starting, but that won't fix anything"

Where did you get the compression test kit, and which one was it? I can't find one locally so will have to order online.

[svsputnik]

Originally Posted by Evan Burkosky

Where did you get the compression test kit, and which one was it? I can't find one locally so will have to order online.

I completely cheated by promising the machine shop to give them the job of remachining the head if they would lend their kit to me. The allowed me to rent it for 100$, which was much cheaper than anything I could find online. Sorry, I don't remember the name or model of the kit

[jimbunyard]

Originally Posted by boatbod

I strongly suggest you do not use any ether as it can cause detonation and a bent rod. A better bet is to hear the intake air using a heat gun and perhaps a whiff of wd40.

Originally Posted by svsputnik

I would second that. Before getting my hand on a compression testing kit, I talked a bit with a certified Yanmar mechanic that told me exactly that. His take was that the safest way to help it start was to basically "create the same effect as a glowplug" by sending hot air for 20 secs in the air intake with a heatgun. He said that if the fuel is reasonably clean and the fuel line has been bled correctly and that the hot air doesn't allow it to start, then it's 99% sure it's the compression that ain't good. And no amount of explosive that you send inside can help it. "You may get it starting, but that won't fix anything"

Starting fluid is a tool like any other; used improperly you can cause damage (to you or your machine), used correctly it can make life much easier.

Spray all the WD40 you want, the auto-ignition temperature of naphtha (WD40s main ingredient) is 437F, you'd be better using a spray bottle full of diesel (A/I 410F). The highly atomized nature of the sprayed WD might be a slight benefit, but that might be counteracted by the CO2 now used as a propellant (ha ha).

Since you've tested and proved that your injectors are working, spraying more combustibles with a higher A/I temp than those that are already in there and that are being added (by the injectors) is more likely to inhibit than promote combustion, especially if compounded with slower-than-required starter speed.

On the other hand, diethyl ether, with an A/I temp of 320F, will certainly combust at a slower speed, or with a lower ambient temperature, or lowered compression ratio temporarily induced by environmental conditions, or even a 'flooded' diesel engine (not entirely correct, but close enough), and used properly as indicated previously will not bend rods or blow off your head or make the engine reliant on it to start in the future (another as-yet-unstated 'danger' of the evil ether).

So...you've already done an impromptu compression test by shooting the injector into the cabin roof, you know your injectors are injecting, you've got the battery charged up and the cables and connections are good, the next step is a half second squirt of starting fluid (2.00 from auto zone or the Japanese equivalent) or hunting down and using a compression tester for a test with possibly equivocal results?...

[Evan Burkosky]

Well, I'm back out at the boat for the weekend and have progressed with diagnosis:

- checked shop manual and found that cylinder head to top of combustion chamber clearance is 0.07 mm
- manual says to check clearance with a crush test by inserting 1.2 mm fuse wire (which I take to be a poor translation of soldering wire) into injector nozzle hole in combustion chamber and turning engine over slowly with hand crank
- purchased 1.2 mm soldering wire at hardware store
- removed injectors, inserted wire into cylinders as per the manual
- wire crushed down to an almost perfect 0.07 mm on each cylinder
- however, crush pattern was very pitted and wire came out black indicating corrosion inside cylinders
- to make sure, double checked crush test with fresh wire
- 2nd crush test also worked, crushing wire flat. Unfortunately in cylinder#2 the wire was crushed so flat I could not remove it back through the hole in combustion chamber. Attempting to pull it out with pliers caused it to break off, perfectly jammed in combustion chamber

So the good news is that the rods do not appear to be bent. The bad news is that the head now has to come off, if only to clear the wire. Most likely this was necessary anyway given the apparent corrosion inside cylinders.

Updated hypothesis:
- a small amount of water did get into cylinders
- the engine was not hydrolocked badly enough to bend a rod
- however engine sat too long with moisture inside causing corrosion of combustion chamber
- head needs to be removed, it and cylinders cleaned, and valves turned
- rings may also need replacing due to damage from cylinder wall corrosion

[jimbunyard]

I can hear the protests before I say it, but if by 'soldering wire' you mean electrical solder used with heat to join electrical parts, if the piece you've broken off in the chamber is small, say 1/2"-3/4" or so or less, and you can clear where the injector seats so it seals, I'd button it back up and just go ahead with an attempt to get it started with the ether.

The small piece of solder won't hurt anything or cause any more damage than might already exist, and who knows, it might just start and run fine after a short while. There's certainly nothing to lose, and the possibility of gaining some valuable information on the actual condition of the engine that no amount of disassembled tests can reveal.

Or you can go ahead and tear it down and chalk it up to experience and
use the knowledge gained in the rebuild as an investment in the future...

[sailah]

They sell small USB powered bore scopes perfect for a situation like this. And they are cheap.

There will always be some texture to the top of a piston from the carbon.

I'd scope it first and compression test it before yanking the head off. I'd do that anyways but I'd want to know why I have no compression i.e from the valves or from the rings. If it's a valve job that's simple, I just did one. If it's the rings, that's a lot bigger job.

https://www.amazon.com/GiraffeCam-Sh...cope+endoscope

[Evan Burkosky]

Update:

- Decided to go ahead and pull off the head. Was quite easy, took almost exactly one hour to complete following shop manual.
- Soldering wire was bent in such a way it would never have pulled out (see pic below). Lesson learned, don't use too much wire when attempting crush test. Easily removed wire with head off.
- Happy I did pull the head. There was a lot of carbon and corrosion, and the head gasket, although showing no signs of rupture yet, looked to be very old.
- Cleaned up #1 cylinder for comparison (see pic below)
- Checked pushrods. All are straight and true.
- Compressed valves slightly to check. Actually seem to seat quite cleanly.
- Large amount of carbon on piston heads, as well as pitting on #2. Need to clean and analyze properly next time.
- Analyzed cylinder walls. Both cylinders are very smooth with no sign of scoring.
- Performed leak test as a rough test of rings. Put both pistons at equal height, midway in cylinder. Poured 1/4 inch of oil into both cylinders. Turned engine by hand forward and backwards several times to work oil in, then let sit. After 5 hours oil had seeped past rings somewhat, but both cylinders still held oil (Note: it's a hot day, temperature in boat was about 90 degrees, so oil was warm and viscous).

Although I haven't purchased a compression test kit yet, the fact that the engine had enough compression to blast injectors out, oil seepage past rings is very slow indicating tight ring fit, no indication of head gasket rupture, and valves relatively clean within valve chamber, I think she just needs a good cleaning. Will purchase new head gasket, clean everything up, and reassemble. Debating whether to turn valves while she's apart.

Pics for reference:
Block: https://drive.google.com/file/d/10KF...ew?usp=sharing

Head (with wire visible): https://drive.google.com/file/d/156n...ew?usp=sharing

One side cleaned: https://drive.google.com/file/d/1_ok...ew?usp=sharing

Leak test: https://drive.google.com/file/d/1DH3...ew?usp=sharing

[Evan Burkosky]

Here's a video as well showing the condition of the cylinders and head: https://youtu.be/jIHSYs7XDqc