2qm20 starting help

[BurningDaylight]

Trying to get my sailboat engine to start. Its a yanmar 2qm20. When I crank it, it'll start and seems to sound good until just after I release the key. Then it stalls and dies. I have the throttle set to full while starting. I checked the bleeder screws and only fuel comes out, no air. Any suggestions?

[Wotname]

How long ago did it last start properly?
What has happened to the engine since then?
Has the fuel system being modified by the addition of an electric lift pump?

[Mattyb]

Blocked filters? When was the last filter change


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[Wotname]

OK, I have just read your OB thread so I'm guessing you don't have much previous history of this engine and that changes things about the best way to help you.

Back to basics, a 2QM20 will run if it has enough fuel, unrestricted air, compression and correct timing. The fact that it starts with the starter motor indicates most things are OK, especially timing and compression.
Lets assume the air inlet is OK ( usually is ), that leaves fuel. Again because it starts, we can assume no air in the fuel system (I think).
Thats leaves only not enough fuel.

Just a guess here, if the mechanical lift pump has failed in the past and an electric one has been fitted instead on repairing the old one, maybe there is a problem there. Can be checked by rigging a can of diesel and gravity feeding it to the injector pump.

Another possibility is a very worn injector pump although I would not expect it to start at all in this case.

As Mattyb suggested, blocked fiters...

Have you tried starting with the throttle closed (idle position).

Can you confirm gear linkage is in neutral when starting.

It is always hard to sort these problems out without history and with a suspect old installation when you have only recently acquired the boat but stick with it, this is a simple engine and you have the collective might of many CF engineers behind you. I must say however, I'm not one of them . Hopefully they with tune in soon.

[capngeo]

Or..... maybe the solenoid is bad... there are two coil circuits; one is the pull back, one is the hold. The pullback is often wire to the "start" and the hold is wired to the "run"

I have found this to be the problem many times when your "symptoms" were present

[Wotname]

Originally Posted by capngeo

Or..... maybe the solenoid is bad... there are two coil circuits; one is the pull back, one is the hold. The pullback is often wire to the "start" and the hold is wired to the "run"

I have found this to be the problem many times when your "symptoms" were present

Are you referring to a "stop" solenoid; if so, good point but I would have thought a 2QM20 would only have a stop cable ie not electric.

Nevertheless, something for the OP to check

[rickpalm]

As you describe the problem I think Capngeo is headed in the right direction. All the Yanmar engines I've worked on had a solenoid attached to a rail that allowed fuel to flow to the high pressure pump. Turning the key to start provides a ground to the solenoid which pulls the rail back and allows fuel to flow to the high pressure pump. When you release the key once the engine starts oil pressure closes a sensor providing the ground to the solenoid holding it open and allowing fuel flow. You might check to see is that solenoid is staying open. If not follow the ground wire from the solenoid to the pressure sensor and see if that is OK. It's an easy wire to pull off while working on the engine.
Good luck

[Wotname]

Originally Posted by rickpalm

As you describe the problem I think Capngeo is headed in the right direction. All the Yanmar engines I've worked on had a solenoid attached to a rail that allowed fuel to flow to the high pressure pump. Turning the key to start provides a ground to the solenoid which pulls the rail back and allows fuel to flow to the high pressure pump. When you release the key once the engine starts oil pressure closes a sensor providing the ground to the solenoid holding it open and allowing fuel flow. You might check to see is that solenoid is staying open. If not follow the ground wire from the solenoid to the pressure sensor and see if that is OK. It's an easy wire to pull off while working on the engine.
Good luck

Hmm... maybe but I have to say I've never seen one on a 2QM20....

These babies will hand start and run without any battery connected; at least so the ones I've encountered.

I agree that this solution does match the reported symptoms!

[BurningDaylight]

Thanks everyone for the comments. I was considering an outboard but I'd really like to get this one going, especially since I managed to get it started. So, i jave no history of the boat other then it hasnt beennrun in about a year. You'll have to bear with me, as this is my first diesel, I do have experience with motorcycles though.

I tried starting at low throttle/idle (or whatever its called). Engine is in neutral. It does the same thing no matter where I have the throttle.

I had opened the bleeder screws to make sure there was no air, and all that comes out is fuel. Where the fuel actually enters the engine behind the air intake, I followed the manual I found online and loosened that connection and there is fuel there, just seems more of a drip. It appears not a lot of fuel, but that may be normal. I don't see any electrical pump on the engine. Just the wiring that runs to the gauges.

I feel like the issue is definitely not getting fuel. The engine runs for between 2-10 seconds after I release the key then dies. So I am going to follow the suggestions above and see what I can find and report back. What a learning experience.

[Wotname]

The 2 to 10 seconds is informative info but unfortunately a fault scenario escapes me at the moment

Almost certainly fuel related though.

[brownoarsman]

Have you checked the throttle linkage to the engine? Just to make sure when you push the lever forward you actually are activating the throttle.


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[Wotname]

Actually more likely an smallish air leak in the fuel supply.
The fact it runns for up to ten seconds indicates that it is sucking in some small amount of air probably before the injector pump

Or

a fuel restriction at the pick up point in the tank.

Sucks up some crud in the tank blocking the fuel pick up, engine stops due to lack of fuel, crud falls away from pick up and the cycle repeats...

[DeepFrz]

When it starts does it rev up or does it just limp along for several seconds? Have you bled right up to the fuel injectors? Are you using clean and new fuel or old stuff from the tank?

You may have to remove the fuel injectors and see what kind of spray pattern they have. Use extreme caution doing this and it helps if you direct the injector so that it sprays into a plastic bottle. Keep well away from nozzle and don't touch the nozzle with your fingers. There are some youtube videos showing how to clean the tip of an injector but probably best to take them to a diesel engine shop.

[BurningDaylight]

Linkage works, checked that earlier today. Good call out though.

Very possible about the clog in the line. Adding that as the first thing I check tomorrow.

[BurningDaylight]

Doesn't rev up, even when I move the throttle up and down.