3GM30F Service Issue

[jssailem]

That sounds eerily familiar. I think in my case the engine is tight and needs some hours of run time. But I’m also going to try and adjust the timing a wee bit. Thinking the hi pressure pump is a hair advanced putting too much fuel into the injectors/cylinders so I’m not getting full combustion at the start. Once running it may be a bit rich but that appears to be ok. I’ve not yet enough time to check fuel consumption. I’m not yet ready to try and put an exhaust sensor into the pipe to measure the exhaust.

 

[Mark Maulden]

to me, this looks like a leaky injector(s)..You shut the engine down and fuel keeps dripping into the cylinder causing a hard cold start. It immediately starts after shutdown as it hasn’t had time to drip drip drip…I had this issue last summer on my newish Beta. (400) hrs. It was starting a bit hard and had white smoke with 10 sec of glow plugs. Normally need 4-5 seconds. Found nothing wrong with the fuel system. On a whim, I pulled the injectors and took them to Northland. They actually said they were fine, however after installation, the engines fires off immediately hot and cold. No smoke. So they evidently inadvertently fixed something during the injectors disassembly/reassembly. And to this day, with a cold start, I can’t push the start button fast enough and its running.

 

[skunther]

The service manager mentioned that the injector pump may have been previously modified by another shop to order to adapt it to the low compression in the cylinders and make the them perform better. He said the rebuild was to spec, and any modifications to the pump would have been lost, possibly explaining why it now starts hard.

Has anyone heard of such a scenario? Does it sound reasonable?

 

[Davidasailor26]

I don’t know enough about fuel pumps to say for sure, but in years of reading forum posts I’ve never seen “adjust the lift pump” as a suggested fix for low compression.

 

[skunther]

I meant injector pump, not lift pump. Sorry, there doesn’t seem to be a way for me to edit the post to correct it.

 

[Davidasailor26]

I meant injector pump, not lift pump. Sorry, there doesn’t seem to be a way for me to edit the post to correct it.

I thought you might’ve. Same concern though - I’ve never seen that as a suggested mitigation for low compression. Maybe it really is and I’ve just never seen it written though.

 

[jssailem]

I would think if the lift pump is weak then you could get fuel starvation at the injector pump. This more likely would kill the engine in the same way a clogged filter kills the engine.

 

[skunther]

I would think if the lift pump is weak then you could get fuel starvation at the injector pump. This more likely would kill the engine in the same way a clogged filter kills the engine.

The engine runs fine once started. The only issue is starting.

 

[dLj]

Just an observation: I'm surprised your engine even runs at 160 to 170 psi compression levels. Those are gasoline engine compression numbers. Diesel engines are typically around the 300 psi compression level. I think the Yanmar 3GM30 should be in the 320 psi region. Now if that was 260 to 270, I would think you might have a case to continue in this quest. But at those compression numbers I think you need a ring job and possibly valves.

dj

 

[Mark Maulden]

Pull the injectors or glow plugs and put a squirt of 40 wt oil in. Replace injectors or glow plugs and see if it fires off..if it does, it would tell you rings are responsible for low compression.

 

[skunther]

I would think if the lift pump is weak then you could get fuel starvation at the injector pump. This more likely would kill the engine in the same way a clogged filter kills the engine.

Wouldn’t that kill the engine when warmed up and idling/cruising too? The engine seems to perform fine once it finally starts…

 

[jssailem]

Wouldn’t that kill the engine when warmed up and idling/cruising too?

Yes. That is why I do not agree that a lift pump is the issue.
Timing is the usual suspect. After you get the engine running the timing being a little off is less of an issue. You may be running. A bit rich. Or Lean which might show up as the engine running hotter than expected. You can test for compression or you can try to tweak the timing. I think you said the color plugs have been serviced. If the timing is not successful then compression could mean new rings are needed. That is not an easy fix.

 

[jssailem]

I think I might be inclined to struggle with the cold starting issue.