Hard Start for a Cold Engine

Starting a Yanmar 3GM30F in the cold

Starting the engine in the winter months has never been easy. There are no glow plugs and this engine now has 2000 hours (still young!) but as engines get older compression is lowered, getting heat into the cylinder for ignition may take longer. I've delved into this fairly deeply now and discovered that warming and lubricating the cylinders before adding compression will help a cold engine fire off nicely, especially when the ambient air is 50 degrees or less.

Diesel engines need heat in the cylinders to ignite/start. Turning the engine over with the compression levers off for about 10-15 seconds puts heat into the engine. Let the engine soak in the heat by waiting 5-10 seconds before turning it over again and generating more heat. By setting the throttle to a faster position say 1/2 to 3/4 throttle, the engine's compression is higher which creates more pressure and heat.

Try different throttle positions for your engine. Every engine is different due to its age and condition.

Here's the slick trick for those cold winter starts:

1. Open 2 or 3 compression levers (compression off)
2. Gear shift in nuetral
3. Shut off fuel at the cockpit control panel
4. Turn key on
5. Run starter 2-3 times for 10-15 seconds each time
6. Wait a few seconds between each 'spin cycle' to allow the heat to 'soak in'
7. Close all compression levers (compression on)
8. Set throttle at 1/2 to 3/4
9. Turn key on
10. Press/engage starter button
11. Engine should fire up in 5 seconds or less
12. Once running, reduce throttle to 900rpm
13. Check to ensure cooling water is exiting the outlet

This sequence should help your engine fire up in a few seconds. If you don't see a significant difference in ease of starting then you may have compression or fuel injection issues. Good luck out there!

Starting above 50F degrees

1. Compression levers on
2. Throttle set to full-speed
3. Gear shift in nuetral
4. Turn key on
5. Press/engage starter button
6. Engine should fire up in 5 seconds or less
7. Once running, reduce throttle to 900rpm
8. Check to ensure cooling water is exiting the outlet
9. If engine doesn't engage within 15 seconds, stop and wait one minute, repeat

Emergency starting (batteries are dead)

1. Throttle set to full-speed
2. Gear shift in nuetral
3. Turn key on
4. Open all 3 compression levers (compression off)
5. Attatch a starting handle/ratchet
6. Spin the engine over 5-6 times counter clockwise
7. IF the flywheel gains momentum...
8. Close all decompression levers (compression on)
9. Turn engine over 2-3 times and engine will start
10. Check to ensure cooling water is exiting the outlet
11. Warm up the engine for 5 minutes at 850 - 900rpm

More info:

• 3GM30F Service Manual
• 3GM30F Operators Manual