Yanmar 2GM20F hard to start.

[Jbwither97]

I have a Yanmar 2GM20F.
About 4-5 months ago the engine became hard to start. Have to give it full throttle for a good 30 seconds to get it to start. But once started it runs fine.
So if I flip the decompression lever on the front cylinder it starts up and I can flip it back over and the second cylinder starts up.
If I flip the back cylinder decompression lever and try to start it I can’t get it to start.
I took the fuel injectors out and turned the engine over and the fuel injector pump seems to be working fine.
I hooked up both injectors out of their holes and they both seem to spray fine. I swapped the injectors and hooked everything back up.
Still hard to start and still can’t get the front cylinder to start by itself.
So I’m guessing it’s either a ring problem or valve problem?
Anybody have enough experience to tell me my next step?
Thanks for any help.

 

[kloudie1]

First would be to make sure the valve clearance (lash) is set to 0.008" at top dead center of that cylinder.. check both while you are at it.. from there it would be a compression check if you are sure the injector is OK.
Another good piece of info would be to turn on back cylinder compression release while the engine is running (after you've set the valve clearances) and see how it compares to the front when running and front is decompressed.. Another cause might be a blown/leaking head gasket, so while you are setting the valves, torque the head bolts in order to the correct torque.. Check engine oil for water and check coolant for diesel.. Good luck

 

[Benny17441]

Yanmar engines raise the temperature of diesel fuel to the detonation point by compression. If there is no adequate compression, the fuel won't burn. Upon Start Up the engine gradually builds up compression by successive revolutions; this rests in the ability of the starter motor to turn the engine fast enough. An engine should start between 4 and 6 revolutions. By advancing the throttle what you are doing is decreasing the engine's resistance to turn by allowing more air (check for air filter and a clean intake tube). Ok, sorry for the worthless intro and now a few suggestions. 1) Make sure the batteries are in good condition and fully charged 2) check the wiring for undue resistance and make sure all connections are clean and tight. 3) bench test if necessary the starter motor. 4) Take notice of the ambient and water temperatures as engine oil will get thicker in colder temperatures enough to slow down cranking. Up North some use engine heaters to keep the oil thin. If everything on the starter side is good then the problem could be that the engine has difficulty building up to the necessary compression. It could be due to improperly calibrated engine valves clearance which fail to seal the cylinder gases or the ultimate head gasket failure or worn rings. We have extended the useful life of worn engines by using oil additives to increase its thickness but the downside is that it will slow the starter down at startup. Since your problem started 4-5 months ago I think it coincides with colder temperatures; if the engine starts up normally after warm up I would attribute the problem to starter cranking speed.

 

[Jbwither97]

I re set the valve gaps and re torqued the head bolts and it does start easier. I forgot to mention that I’m getting a layer of black soot on the water maybe every other start up.
I order a compression adapter for the fuel injector hole so I guess I’ll see what the compression is and go from there.

 

[Whatfiero1]

A Diesel speciality shop can test your injectors to see if preform well it was $25 each for mine and an additional $100 each to rebuild. Came back to me with all gaskets o rings to put back together starts better now

 

[JamesG161]

Check for water in your engine oil too.
Jim...

 

[Jbwither97]

I just ordered a new injector someone was selling for $50 on EBay and I might just have one of the old ones rebuilt if it’s $100. I’ve checked the oil and all still looks good. Just waiting on the compression adapter.

 

[Whatfiero1]

You really can't tell by looking at injectors which ones bad. It's the spray pattern the best way to check is the decompression levers. Start it cold and cycle thru levers if only run on one the other is bad. Then get it hot and check again it will stay running but run rough on the same one. That's bad or dripping injector.

 

[Benny17441]

Once the engine warms up is it still difficult to re-start? If your exhaust port is below the waterline when cranking the engine let is rest every 5-10 seconds as continuous cranking could suck up water in the cylinders.

 

[Jbwither97]

Exhaust is above water line.

 

[reworb]

Have you checked the part of the wiring harness that goes from/to the starter button and the starter motor. Those harnesses are notorious for causing hard starting once they get 10 years old or so (cheap wires and too many connections).

 

[Jbwither97]

Yep, the wire harness started to fail months ago and I ran a new larger wire. I swapped the injectors and it runs the same. If I start it up and decompress the front cylinder the engine continues to run. If I start it up and decompress the back cylinder the engine immediately dies. It was the same with the injectors in their original cylinders. So I’m assuming the compression is so low in the front cylinder that it requires the back cylinder to give it that extra torque to keep it running.

 

[Davidasailor26]

Exhaust is above water line.

Still need to be careful when cranking to long. The problem isn't really water getting sucked up the exhaust, it's the cooling water getting pumped into the exhaust. Without combustion there's not enough pressure to push that water out the muffler, so it can back up into the cylinders.

 

[NYSail]

What davisasailor said...... also have you checked your mixing elbow? Too much back pressure will also add to difficulty starting and will leave soot.
Greg

 

[Panera]

I was having trouble starting mine, I also had diesel drips under the engine. My problem was fuel related, compression washers needed to be replaced. This was allowing air into the fuel line. Look for any drips, if so, replace all the compression washers in the fuel lines; lift pump, fuel filter...