I have gotten my new to me 3gm30f running after it sat for 15 years. All I have done is replace the primary racor filters, the secondary filter, air filter element, oil and oil filter. I am pulling fuel from a 3 gal gas temporary tank until I finish cleaning the old monel tank. With the throttle lever at idle position tach shows 2000 rpms, steady rpms but seems to shake a little too much. Smooths out and looses shake at 2300 and sounds great all the way to 3500. Seems to have more in her but did not push her over 3500 for now. I went below and adjusted the throttle stop bolt/screw to get below 2000 rpms. I got to 1400 but anything below would cause the motor to stall out, first shake badly, then stall. My suspicion is that she is fuel starved at low rpm, or my tach is wrong, with my gut telling me the former. I am inclined to buy a photo tach to rule out the later, but my bet is that the tach is not the issue. Thanks for all feed back. Matt
Low idle 3gm30f
- Thread starter GABristol29
- Start date
My guess would be the tach. Someone would've really needed to play with the idle to get it all the way up to 2000. Also a diesel isn't like a carbeurated gas engine with high and low speed jets. If it can get enough fuel at higher speeds it should be able to do so at lower speeds too.
1. If you are running outside the normal fuel supply system, have you then omitted the lift pump? If so, the injector pump might be struggling to get fuel at low rpm.
2. Some of those old Yanmars have the bottom of the throttle as the stop position. That is, put the throttle to the bottom to stop the motor.
3. Motor has been sitting. Fuel system clogs may lurk where you haven't yet looked, plus injectors may need cleaning.
Last: you said "gas" can. I'm sure there's diesel in the can
2. Some of those old Yanmars have the bottom of the throttle as the stop position. That is, put the throttle to the bottom to stop the motor.
3. Motor has been sitting. Fuel system clogs may lurk where you haven't yet looked, plus injectors may need cleaning.
Last: you said "gas" can. I'm sure there's diesel in the can
How are you measuring RPM?? Tachs run from the alternator can be way off. Get a $30 optical tach at harbor freight and check your real RPM before too much adjustment.
Leslie, tach is measuring at flywheel, not alternator, but I still plan to check with laser.
Skipper, I am running the fuel from an actual temporary plastic gas tank (with diesel), return fuel line is directed to main monel tank for now. The lift pump is in the loop (but it is possible that is not doing its job at low rpm...). Re. engine stop, it is not attached to throttle - it is separate and, from what I can tell, stops fuel flow to stop engine. Injectors likely need cleaning - is that a big job?
Thank you all.
Matt
Skipper, I am running the fuel from an actual temporary plastic gas tank (with diesel
), return fuel line is directed to main monel tank for now. The lift pump is in the loop (but it is possible that is not doing its job at low rpm...). Re. engine stop, it is not attached to throttle - it is separate and, from what I can tell, stops fuel flow to stop engine. Injectors likely need cleaning - is that a big job?Thank you all.
Matt
I'd say pull the injectors and have them rebuilt. I just did mine and she went from trying to jump off the motor mounts to purring like a kitten. An extremely loud and clattering kitten, mind you. But so much better.
To reinstall your rebuilt injectors, you'll need:
3 124950-11450 GASKET, CHAMBER
3 24341-000260 O-RING 1A S-26.0
6 23414-080000 GASKET 8, ROUND
Torque the pipe joint bolt to between 112 and 147 inch-lbs. Don't screw up the conversion from newton-meters like I did or you'll also need 3 105582-59150 BOLT 8, PIPE JOINT, and a bolt extractor.
Mike
To reinstall your rebuilt injectors, you'll need:
3 124950-11450 GASKET, CHAMBER
3 24341-000260 O-RING 1A S-26.0
6 23414-080000 GASKET 8, ROUND
Torque the pipe joint bolt to between 112 and 147 inch-lbs. Don't screw up the conversion from newton-meters like I did or you'll also need 3 105582-59150 BOLT 8, PIPE JOINT, and a bolt extractor.
Mike
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Thanks Mike, checking on those parts now. And thanks for the conversion warning - a mistake I would make. Matt
simple. it's either injectors of fuel pump assuming the compression is normal.
it's cheeper to start with injectors
just had my fuel pump rebuilt last summer. it was the second time for my 50+ year old perkins 107. ain't cheep, but what is?
it's cheeper to start with injectors
just had my fuel pump rebuilt last summer. it was the second time for my 50+ year old perkins 107. ain't cheep, but what is?
Thanks Jon. And re. Mike's post with part numbers, please see the following, numbers searchable using "Ctl F" on your keyboard: https://j109.org/docs/Yanmar-3GM30-parts-catalog.pdf
Good info here. But do find a way to get accurate RPM readings before you spend money on anything. That engine has not been started in 15 years ! It could be gummed up from the lift pump to the HP pump to the injectors, including the fuel lines !
Please refrain from pushing it neutral ! Engines are made to work under load. With the correct prop and everything in good order, those 3GM30F will rev to 3400 or 3600 under load and that is normal. Higher or lower means wrong prop or something else causing the problem. I would get a second jerry can and run the return line to it to see if there is something in the fuel being returned as the engine is brought to normal operating temp. Good luck
Please refrain from pushing it neutral ! Engines are made to work under load. With the correct prop and everything in good order, those 3GM30F will rev to 3400 or 3600 under load and that is normal. Higher or lower means wrong prop or something else causing the problem. I would get a second jerry can and run the return line to it to see if there is something in the fuel being returned as the engine is brought to normal operating temp. Good luck
Claude - thank you. Good thought to rig a second jerry can and have a look. I will check RPMs too.
Matt
Matt
