Yanmar 2GM Won't Fire - Troubleshooting

[Evan Burkosky]

Looking for help troubleshooting my old raw-water cooled Yanmar 2GM. Here are the symptoms and circumstances so far:

Circumstances:
- sailed to offshore island with a friend. Just outside of harbor went to start engine and starter burnt out in a puff of smoke.
- with zero wind could not sail into harbour. With prevailing current onshore needed to get engine started asap.
- flipped up decompression levers, attempted to start by hand cranking, in my haste *forgot to close raw water inlet*.
- after several valiant attempts to hand crank, no skin left on knuckles, and rocks approaching, dropped anchor to await a tow.
- no starter parts available on island. Dissasembled starter, cleaned brushes to no avail, starter was dead.
- after two days couldn't wait any longer, rowed her out of harbour with the dinghy, sailed home.
- various obligations kept me busy through the ensuing winter. It was 8 months later when I finally installed a new starter and tried to start her again. During that time she sat as she was.

Symptoms:
- after installing new starter she wouldn't crank at all. Tried with hand crank and found she was seized.
- checked oil and found crankcase overfull. Oil flowed out of crankcase when dipstick removed.
- tapped on hand crank with large hammer. After a few taps she started to free up. Continued tapping through one revolution untiil she freed up enough to turn over normally.
- removed oil fill cap on rocker cover to observe rocker movement. Rockers moving as expected.
- tried starter, she cranked over fine.
- checked turning by hand crank with and without decompression levers up. Compression strong.
- bled fuel system completely. Certain no air in fuel lines.
- tried starting. Would not fire at all.
- pumped out oil and replaced several times with fresh until system clean.
- stored oil in glass bottles. After sitting oil separated to top revealing mayonnaise like substance in bottom centimeter of jars.
- pumped out fuel tank and lines of all fuel, replaced with fresh diesel, rebled system.
- tried starting several times, will not fire at all. Not one pop.

Hypothesis:
- Hand cranking with raw water intake open allowed water to enter cylinders.
- After sitting for 8 months water seeped down past rings and gathered in crankcase.
- Resulting corrosion resulted in at least one seized piston.
- Top end corrosion resulting in improper injector and/or valve operation leading to lack of combustion.

Based on the above circumstances and symptoms does this hypothesis sound accurate? What are the next steps to diagnose? I plan to remove head and thoroughly inspect and clean, then re-install with new head gasket. What should I watch out for? Boat is on a mooring, very far from the nearest mechanic, and I'm operating on a tight budget.

Appreciate any help!

[model 10]

I would keep trying before tearing it apart. You have allready scraped off the loose rust so not much harm from getting it started now. If it has compression you should be good to go. Give it a shot of starting fluid. It it fires you know you have fuel problems.

[four winds]

You're summary is thorough and clear, a good post.

I wonder if the injectors are the issue. Could corrosion have fouled them? Maybe pull one and hook it back up to check the spray while hand cranking.

Maybe corrosion couldn't stop such a high pressure pulse off fuel, I don't know. Just thinking out loud.

[Wotname]

I concur with the above two posts.

Remember a diesel only needs three things to fire
Air
Fuel
Compression

So yes, keep trying before pulling apart and pull an injector to check the spray pattern.

Pulling an injector maybe time consuming as there is every possibility that it is "stuck" in place due to long term corrosion but it will come out with enough persistence but please don't resort to the big hammer with an injector. There are delicate things inside.

[Evan Burkosky]

Thank you for your replies everyone! I've continued troubleshooting the injectors.

Steps taken so far:
- removed exhaust elbow to ensure no blockage. Elbow was clear (expected, as replaced last year).
- removed alternator belt for easier cranking.
- removed fuel line at injectors to ensure steady stream of fuel is reaching them (see video below Yanmar 2GM injector test part 1).
- removed #2 injector and installed upside down to check spray pattern. Spray pattern looks good, nice cylindrical shape, strong jet (see video below Yanmar 2GM injector test part 2).
- cleaned carbon with a toothbrush and reinstalled #2 injector.
- removed #1 injector and tested spray pattern. Not clean like #2, irregluar shape (see video below Yanmar 2GM injector test part 3).
- cleaned with toothbrush and reinstalled.
- reassembled and tried to start engine, still does not fire

*Note: removed injectors by first removing retaining bracket, then hand cranking engine. Engine compression forcibly ejected injectors (bounced off cabin roof!) indicating at least fair compression remains.

You can see the results of the above tests by watching the following videos:

Yanmar 2GM injector test part 1: https://youtu.be/hIIQAYFY1FI
Yanmar 2GM injector test part 2: https://youtu.be/7ptJI7x5XEo
Yanmar 2GM injector test part 3: https://youtu.be/JFu2i1KOaIk

[newhaul]

Have you tried starting fluid yet as suggested. Had an old bmw that needed either to start after setting for a few hours.

[Evan Burkosky]

Update - starter fluid test:
- tried spraying 5-56 (WD-40 is hard to come by in Japan) into air intake while turning engine over with starter.
- engine emits dense clouds of white smoke but fails to fire.

*Note: the Yanmar 2GM does not have glow plugs.

Revised hypothesis:
- starter originally burnt out due to hydrolock.
- the offshore passage completed prior to burnout was the longest passage I'd made in a large following sea after installing new exhaust system and waterlock last year. New waterlock may not have been functioning correctly and let water into cylinders.
- I did not notice hydrolock at the time because prior to attempting to start via hand cranking I first opened decompression levers. Any water in the cylinder at that time would have been driven out open exhaust valves.
- fail to start and white smoke caused by loss of compression, either by valve corrosion or damaged rings.
- next step obtain Yanmar 2GM compression test kit and check compression.

Does anyone know the part number for the correct Yanmar compression test kit?

[newhaul]

Try actual starting fluid (either) wd40 will help with compression but not so much with fireing ( and helping diagnose fuel issues) try preheating air with propane torch at the intake.

[sailorchic34]

Sounds like the engine was hydrolocked. Odds are one or both connecting rods are bent which lowers compression enough so the fuel does not combust.

[Wotname]

^^ gotta agree with Sailorchic.

You have fuel (and the timing shouldn't have changed).
You have air
Therefore the compression must not be high enough.

The compression creates the heat so perhaps one way to test this hypothesis is by either adding heat (by way of hot air gun or hair dryer into the air intake) or by artificially increasing compression. Pop the injector again and add a couple of cc of engine oil. Refit the injector and see if that cylinder will fire. Obviously you mustn't add too much oil but I think 3 or 5 cc (teaspoon full max) would be OK.

[Evan Burkosky]

Yes, seems to have been narrowed down to a compression issue. I'll get a compression test kit to make sure, then pull the head. Hoping for valve corrosion leading to a top end rebuild over bent piston rods or damaged rings, as that would allow me to leave the block in the boat and just take the head to a shop. Will report back after a compression test.

Again, if anyone knows the part number or where to find the Yanmar 2GM compression test kit it would be much appreciated!

[RaymondR]

Originally Posted by sailorchic34

Sounds like the engine was hydrolocked. Odds are one or both connecting rods are bent which lowers compression enough so the fuel does not combust.

Possible.

Another possibility is that the rings are corroded into their slots and not sealing and consequently not enough compression for compression ignition.

Sounds like a full tear down and rebuild and you will probably cause more damage by persisting with attempting to start it.

[boeing1]

agree with checking compression with tester,

[Martkimwat]

How much throttle are you using to attempt a start? Usually as compression drops of, so you need more throttle to get it to start, in fact it's a reasonably reliable indicator of how good your compression is by how close to idle you can start the engine (from cold)

[jimbunyard]

I'm guessing diesel saturated cylinders and slow starter speed. Check that cables and connections are good, and that battery is topped up. Turn the engine over in a no fuel setting, with the decompression levers open, for about 15-20 seconds, 3 times (don't overheat the starter). Get some real starting fluid, squirt just a little puff into the intake, and try again. Be ready to operate the throttle to provide fuel if it fires. When (and if) it catches, expect it to run rough for a little as the rings and valves reseat themselves