2 cylinder yanmar help

[01kiwijohn]

That's the torque capsule, don't touch that if you don't know what you're doing.
I just had a similar case and it turned out that the owner had not quite bled all the air out of the injector pump housing. It doesn't take much, just a couple of bubbles. Once bled, it fired right up.

[Cheechako]

Messing with the Injector Pump was not a good step. Hopefully you can figure this out.

The other thing to keep in mind is the GM series suffers from cracked piston issues. When cracked, they start hard and come up to speed slowly if they start. In a 2 cylinder, that may be worse.
I wouldn't jump to this conclusion, but an engine that ran and then didnt ... it could be...

[motion30]

I was able to get it to the point where it starts but it will not stay running or develop any RPM certainly that injector limit screw is an issue. But I don't feel I'm getting enough pressure out of the injector pump I guess I will try to bleed more

[Matsubob]

The GM series Yanmar's are great little engines! But that injector pump's design is the worst. The cast iron body is solid but the already mentioned pin and fork MUST be engaged. And there is only one place where the pin on the injector pump body will go through the slot in the top of the front case. Positioning the fork to receive the pin on the injector pump is done by moving the "shut off" lever until the fork is in line with the cutout in the top of the case. Then the injector pump has to be dropped straight down onto the fork while sighting its position until the two are engaged. It is true that there is no way to know if it has engaged or not. If it is not engaged, the pin on the injector pump will end up either in front of or behind the fork, putting the throttle in either WOT or IDLE plus a few RPM's. It is pretty scary, having a runaway engine, down in the depths of the hull with the only way to shut it off being the petcock on the fuel tank! (don't ask how I know!)
Installing the injector pump is straightforward if you can stand right over the engine and place it down onto the front engine case. Not so much if the engine is in its compartment and you have to guess whether the receiving fork is positioned correctly. (don't ask how I know!) The problem is, you have to complete the installation pretty much before finding out, and if it isn't engaged, it means tearing it back down to where you started. (don't ask how I know!)
Once that is complete, bleeding the first filter, then the one on the injector pump and then the injector line fittings is necessary to be sure it will run. Sometimes, bleeding the line nuts on the injectors isn't necessary because there is enough pressure from the injector pump.

[motion30]

Yes it is fortunate enough there was a little cut out that can be removed to look down and see the fork, it must be all the way over to the port side I am reasonably sure I did get that engaged I just don't seem to get any pressure out of the fuel pump it seems to just spit a small bit of fuel. I don't know how much fuel it is supposed to move. And yes perhaps there's still air in the system. Like I said it will now consistently start but it just won't run

[Cadence]

I'm afraid more problems were created than fixed.

[Foredeck]

It's got air between the fuel tank and the fuel filter. Between them is the FUEL LIFT PUMP. This pump will bleed air & pump fuel up to the filter.


1. Pump lever is at the aft side of the pump - it's a flat thing sticking out of the lift pump.
2. Crack the bleed bolt on the fuel filter.
3. Pump the lever - all the way down on every stroke
4. If you don't get air bubbles at the bleed bolt after, say 10 minutes of vigorous pumping, manually rotate your engine 1/2 turn & start again.
5. When you start getting fuel coming out of the bleed bolt, keep pumping while you tighten it.
6. Crack the bleed bolt at the entrance to the high pressure pump.

Pump fuel lift pump until it is pissing fuel.
7. keep pumping while you close that bleed bolt - and do an extra 10 0r 15 pumps after (this will prime the high pressure pump)
8. Your engine will start and hold revs. If it doesn't, horse the throttle for a bit until it steadies up.


Info from a racer who has been known to not carry enough fuel to keep the system primed when heeling for long periods upwind.


good luck.

[motion30]

Foredeck
The mechanical lift pump is not in service it was replaced by an electric pump. So I will start from the beginning and bleed the fuel filter and continue up the chain until I get to the injectors.
When I first looked at this in yesterday it would crank but not fire at all. Least we got it to the point where it will start so I feel like I'm making some progress

[Wotname]

If you want to confirm you have bled all the air from the system, you can pull an injector (and leave it connected to the injector pump after removing it).

Now turn the engine over with the hand crank (and the other cylinder decompressed) and with the throttle at full open (WOT). You will see the spray of diesel from the injector. Compare the amount of spray at the idle setting and also with the stop lever operated.

Of course, keep body parts away from the injector nozzle and don't smoke

EDT: I guess this could also tell you if the fuel rack positioning others have mentioned is correct or not?????

[jimbunyard]

With an electric lift pump, it is unlikely that you're having problems with not enough fuel to the injection pump. The injection pump does not pump very much fuel per stroke, something on the order of .06594 cc/stroke per injector.



That is calculated from the stroke and the diameter of the p&b; I believe the about 22cc shown in the chart for a 2/3 gm is total/minute for the engine.

I'd guess that either the rack pin is not engaged in the slot, one of the regulator springs is broken, or the injection limiter is badly out of adjustment.






Not sure if you have a 2gm20, but if you do, a complete service manual is available here

http://www.google.com/url?sa=t&rct=j...SZZDU88HTkjZv2

[motion30]

I'm 85% sure the rack is engaged. What I am 100% sure is the previous owner remove the fuel injection limiter screw. Does anybody have one of these motors they could measure and least give me a bassline on this screw I figured that's what the problem mostly likey is.

[motion30]

Originally Posted by jimbunyard

With an electric lift pump, it is unlikely that you're having problems with not enough fuel to the injection pump. The injection pump does not pump very much fuel per stroke, something on the order of .06594 cc/stroke per injector.



That is calculated from the stroke and the diameter of the p&b; I believe the about 22cc shown in the chart for a 2/3 gm is total/minute for the engine.

I'd guess that either the rack pin is not engaged in the slot, one of the regulator springs is broken, or the injection limiter is badly out of adjustment.






Not sure if you have a 2gm20, but if you do, a complete service manual is available here

http://www.google.com/url?sa=t&rct=j...SZZDU88HTkjZv2

Thank you very much for the service manual it is just what I needed

[jimbunyard]

85% seems rather long odds to me.

Screwing the limiter in reduces rack movement, so a starting place would be to put the 'regulator lever' at full fuel and then screw the limiter in until you feel it just contact the 'control lever' via the 'regulator springs'. This will also tell you if the springs are compromised. These springs are very important as they are the only connection between the 'regulator lever' (the throttle arm) and the 'control lever' and hence the injector pump rack.

A very good description of servicing the entire fuel system, down to disassembling the injection pump itself, is contained in the Yanmar service manual referenced earlier.

[skipperpete]

I just physically measured the thread protrusion of the fuel injection limiter after removing the acorn nut/ dome nut. The distance from the timing cover to the end of the threaded limiter on 2 separate 2GM 20 engines is 18mm and 19 mm respectively. On my 2 engines there is a small hex head on the end of the threaded adjuster and the 18/19mm is from the top of this hex to the surface that the copper washer sits on at the timing case. I still have a slight concern re the rack pin and yoke/ fork possibility due to the fact that one potential result of mis alignment is catastrophic overspeed failure that can't be stopped by blocking the air intake due to the crankcase breather connection. Opening the injector pipes works but you only have milliseconds to accomplish this.

[motion30]

Skipper Pete I thank you so much for taking the effort to measure that screw. That helps me get a ballpark. I am going to go over to that boat again tomorrow and try to get it running your help is invaluable thank you so much