2GM20F Starting? - SailNet Community
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post #1 of 13 Old 06-30-2012 Thread Starter
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2GM20F Starting?

Dear Forum:

I want to know if what I am about to describe here sound like I have air in my fuel system.

It has been hot here in Oklahoma with 100 degree weather. It takes 4 or 5 attempts on the starter for a couple of seconds each before my 2GM20F picks up. Once running, it sounds good with plenty of power. If the weather were cooler, it would be a little more difficult to start.

While the engine is trying to start, there is no excessive smoking. Once the engine starts, is runs nicely, smoothly, with power and no visible smoke at all; there is no excessive smells either. It does seem to run at a faster idle than my friends 2GM20F. If I try to start the engine within a couple of hours of it having run, it will start right up. If left over night it takes several attempts.

Does that sound like an issue with air in the fuel system? Or does something else sound more likely?

I am really interested in knowing if what I have described closely approaches what one would experience if air were in or around the injectors. Or said another way, how would the engine perform if there were a little air in the system and could it cause the symptoms I have described?

A follow up to that is this question: If there were a little air in the system and the engine starts and runs nicely once started, then wouldn't the air soon be removed and not be an issue assuming that there is no small leak or point of subsequent air intrusion? Let's say that there is a little air in the system but the engine starts; then, if once the engine starts and there is no re-introduction of air into the system, will the engine have cleansed itself of the original air?

Sorry to belabor this so. Experience is such a better teacher but, good instruction softens the consequence and improves the experience.

Thank you for your reply,

Steve
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post #2 of 13 Old 06-30-2012
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Re: 2GM20F Starting?

It's not air in the fuel system. If it was all most all the time the engine would not start or if it did would run very very rough. Air in the injectors does not allow fuel to be injected into the cylinders so then the motor will not start. Diesel fuel is injected into the cylinder at very high pressure. Because fuel is a liquid it will not compress but opens the injector valve allowing the fuel into the cylinder. Air on the otherhand is a gas and is compressable. When the fuel is pressureized to open the injector valve the air compresses so that there is not enough pressure to open the injector.
It sounds like, you're not staying on the glow plugs long enough.

Last edited by ebs001; 06-30-2012 at 06:02 AM.
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post #3 of 13 Old 06-30-2012
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Re: 2GM20F Starting?

What is your throttle setting? When I first got my boat with a 3GM, I had the same sort of problem. Once I learned to start it with some throttle the problem went away. You can't 'flood' a diesel engine. If your starting the engine with the throttle set at idle try giving it some gas and see if that works. Just be ready to drop the throttle to idle as soon as it starts.
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post #4 of 13 Old 06-30-2012
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Re: 2GM20F Starting?

saillife is correct. Your Yanmar does not have glow plugs and you need to advance the throttle prior to starting. It's in the manual.
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post #5 of 13 Old 06-30-2012
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Re: 2GM20F Starting?

It could be air. I had a 3gm in the last boat and it did exactly what you are describing. After bleeding several times with no improvement we found that there was a wee bit of a diesel leak at the secondary fuel filter on the engine (not really a leak, just enough to make your finger shiny when you reached under). Replaced the O-ring and solved the starting problem, must have been getting a little air if not run for a day or more.

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post #6 of 13 Old 07-01-2012
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Re: 2GM20F Starting?

Had same problem with older 2QM 15h/p engine and cost me $20aus. to purchase workshop manual which mentioned this same hard starting fault. So on their advice I adjusted the valves (very easy operation) and told to use half throttle on first start up. 2year problem now fixed
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post #7 of 13 Old 07-01-2012
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Re: 2GM20F Starting?

Suggest to go over either replace/re-tighten all your banjo bolts, bleed points, filter o-rings and copper washers. After that bleed your injector high pressure lines(don't know if the 2M has compression releases). There should be no bubbles in your fuel when bleeding. Suggest to bleed the fuel system at least 3 or 4 times.Technique suggested "partial throttle" should only be used in cold temp starts. Warm temp starts should not require any throttle openings.
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post #8 of 13 Old 07-01-2012
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Re: 2GM20F Starting?

i Have 2 Yanmars in my life. I keep them separated and one doesn't know that the other one exists. One is on my Beneteau 311 and the other John Deere 2210 and they are both 2003 build. The Deere has 630 hours on it and the boat 480 hours. Anyway, to get to my point Why is the Deere so much easier to start and sounds so much more powerful and solid?
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post #9 of 13 Old 07-01-2012
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Re: 2GM20F Starting?

Check the banjo fittings as suggested above and give it half throttle at least when starting. Also check the fuel line all the way back to the tank, especially the crappy plastic elbow that leads into most tanks. I had a hairline crack in this. It had me pulling my hair out. Similar symptoms. When is the last time you adjusted the valves?

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post #10 of 13 Old 07-02-2012
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Re: 2GM20F Starting?

When where the injectors checked for proper spray pattern, pressure openings and tips checked?
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