3gm30 runs wide open

[wbmiller3]

My 3gm30 runs wide open when started. No black smoke, oil level is fine...was sitting for several months before this happened. Fuel shut off and throttle arm on pump are both ineffective. Scared the hell out of me. Killer with decompression levers. Pulled breather and restarted with same results, this time I killed it by restricting intake air. I'm suspecting something stuck in the fuel pump. Anyway to check this without pulling the pump?

Thanks, Wayne

 

[Rob19574]

Wayne - its runaway diesel. Somehow your engine lubricant oil is making its way into the compression chamber and your getting combustion. Any work done on the engine recently? I had this same issue and it was caused by a faulting oil-breather line that was incorrectly installed -- it was feeding oil into the compression process. Old or faulty rings can cause this too. Can you provide any additional detail? How old is the motor? Are you low on oil? Has there been any work done on the motor recently?

 

[wbmiller3]

I've read about that...don't think that's the case here

I know what your referring to and thanks for the reply, but I don't think that's happening here. Engine is running perfect, no discolored exhaust smoke, oil level is fine. Rings are seating well, it's a low hour motor (under 400). It had set up a year prior to this happening. I think the fuel rack is stuck in the pump but don't know how to check it. From what I've read when they start sucking lube oil by the rings they smoke like a junkyard burning tires. This thing sounds great with very little exhaust color.

 

[kloudie1]

Check the linkage/ cable clamp to make sure it hasn't slipped and is returning the lever on the engine to "idle" when you ask for that.

 

[crosswind]

Have to say i have some experience here having rebuilt my fuel injector pump (stupidly I might add), but after reassembling it a few times to get it right discovered an interesting phenomenon with the yanmar injector pumps.

There is a small pin that goes through the housing keeping the cylinder chamber in its proper place and it can back out allowing the timing between the cylinder and the chamber to be out. The result of this is exactly what you are describing. The engine will run full RPM with no control from shut off or throttle.

The good news is it is a very easy fix. Simply push the pin back in and use your own special method to prevent it from backing out again. (***** punch/adhesive/whatever).

The bad news is you have to remove the injector pump and disassemble it to get the pin in place. It's tricky but with the service manual and a good acumen, it can be done.

Reach out to me if you need the manual as I have it in PDF. format. Also we can talk it through verbally if you chose to go this route.

IMHO as always.

CW

 

[Steve Dion]

I'm with Claude. Check the throttle cable at the engine and be sure that it is in the slow/idle position. Once you know that it is not the problem you can start looking at other options.

 

[wbmiller3]

Thanks Guy's, I'll pull the pump tomorrow. Might need some more help when I get it home. I've got the Yanmar service manual for the 3gm but I'm not sure how detailed the pump section is.

 

[kloudie1]

Good luck ! Post a couple of pix when ya find it !!

 

[wbmiller3]

will do, btw it's not the cable or clamp I moved the actuator arm at the pump back and forth manually to no effect.

 

[wbmiller3]

help...pump won't come out

I've got everything off the pump, removed the 4 nuts on top but it won't come off. Feels like its spring loaded and wants to cock to one side or the other. I try to use screwdrivers and lift it up evenly but it feels like something is catching and it won't lift off. It may be associated with why it's running wide open. I dunno...don't want to force anything. Manual gives the impression that it should just lift up and off. Any advice?

 

[wbmiller3]

Pin won't clear housing?

Have to say i have some experience here having rebuilt my fuel injector pump (stupidly I might add), but after reassembling it a few times to get it right discovered an interesting phenomenon with the yanmar injector pumps.

There is a small pin that goes through the housing keeping the cylinder chamber in its proper place and it can back out allowing the timing between the cylinder and the chamber to be out. The result of this is exactly what you are describing. The engine will run full RPM with no control from shut off or throttle.

The good news is it is a very easy fix. Simply push the pin back in and use your own special method to prevent it from backing out again. (***** punch/adhesive/whatever).

The bad news is you have to remove the injector pump and disassemble it to get the pin in place. It's tricky but with the service manual and a good acumen, it can be done.

Reach out to me if you need the manual as I have it in PDF. format. Also we can talk it through verbally if you chose to go this route.

IMHO as always.

CW

I wonder if the pin has backed out so far that I can't get the pump out because it's hitting the housing when I lift it up?

 

[inprin]

Similar problem

I don't mean to hijack this thread but my problem may be the same. I just rebuilt a Yanmar 1GM10. A complete Head job, honed the cylinder and new rings, etc.. At startup it acted like a runaway engine. Very high RPM and lots of black smoke. The kill switch did not stop it and any adjustment to the fuel accelerator just made it run faster. I choked off the air intake and it almost stopped it but as soon as I loosened the fuel line at the injector it stopped. This tells me it is getting way too much fuel. Am I correct? I did not replace the fuel injection pump as it was working fine before my rebuild. How do I check if the fuel injector pump is working properly?

 

[crosswind]

The output coupling where the high pressure fuel injector line connects to the injector pump is a torque specific connection. On my YSM12 the setting is anywhere from 28-32 foot pounds. It effects the fuel volume pushed to the injector.

 

[crosswind]

I wonder if the pin has backed out so far that I can't get the pump out because it's hitting the housing when I lift it up?

Sorry for delay in response. Traveling a lot.

I don't think the pin is preventing the pump from coming out but there is a spring loaded pin which pushes against the rail mechanism acting as your governor. It will bind up if u don't reach in through the oil fill cap and manually retract it.

 

[RichH]

I've got everything off the pump, removed the 4 nuts on top but it won't come off. Feels like its spring loaded and wants to cock to one side or the other. I try to use screwdrivers and lift it up evenly but it feels like something is catching and it won't lift off. It may be associated with why it's running wide open. I dunno...don't want to force anything. Manual gives the impression that it should just lift up and off. Any advice?

The injection pump is linked/connection to the engine's governor, and that linkage must be disconnected before the injection pump is removed. There is a cover plate just above the injection pump that will allow access to the injector pump linkage with the governor.

The injection pump rack has a pin on it, which connects to the governor and is held in place by a small spring wire clip (in the shape of the german letter 'double S' = ß). Youll need a 6" long 45° 'bent' needle nosed pliers to disconnect the ß. You will most likely inadvertently drop the ß into or deeper than the injector pump - removing the pump will allow you to find the ß.

The high pressure feed lines from the pump to the injectors will have to be 'moved' out of the way in order to work inside that cover plate.

Try not to disturb the 'shims' between the pump and the engine block, as these are what sets the engine 'injection timing' !!!!!!!!!

Once the cover plate to access the injector pump control linkage is gained, the governor linkage disconnected ... you really dont have to remove the injector pump to check if the pump's fuel rack is binding or not - just reach in with a contorted finger and slide the rack back an forth to feel for resistance or binding as you slide the rack back and forth. Sometimes also removing the governor's access plate will make it easier to get the governor linkage back onto the injection pump rack (.... and getting the linkage out of the way to find the dropped ß).


Have 'fun' removing and reinstalling the injector pump several times - after you drop that damn ß several times as it bounces 'deeper' into the engine internals.

Of course the side clearance of the engine to a wall/bulkhead will be 'close' and you'll appreciate the lack of side clearance to the engine's side - NOT.

 

[wbmiller3]

pumps out...had to pull front engine cover

Well the pumps out. Wasn't easy even with the front engine cover (timing gear cover?) removed. The fuel rack itself was too far out of the pump to clear the case when you tried to raise it up. Unfortunately we broke one of the forks on the lever arm that slides the pin back and forth (which is in the fuel rack) off. I trhink I can tig a replacement piece in its place. Even with the pump off and thoroughly sprayed with PB Blaster the rack is difficult to move back and forth. You have to tap it with a small hammer and drift pin. The center (I'll call it a roller-lifter for lack of the correct term) seems collapsed as well. #1 and #3 are extended and spring loaded, #2 while still somewhat "springy" will fall back into the pump if you turn it over, #1 and #3 will not do this. Think I'm looking at some pump repairs...any contacts? If anyone would benefit from some pics post a reply and I'll stick some in. BTW it's a pain to full your front cover with the pump in, pull up the pump as far as you can and slowly turn the engine over to get the cam lobes off the pump rollers while wiggling the case off (an extra set of hands would have been real nice here). Whats weird is that everything looks super clean and well lubricated, no visible corrosion anywhere, of course I can't see the rack inside the pump and I know the fuel had some water in it as the separator was almost full. The back side of the rack is geared and must move something inside the pump as it moves front to rear, this is where the problem is, everything else looks great.

 

[RichH]

Suggest you seek out the largest injector shop, one that caters to truckers, as a complete rebuild of your pump is in order. Every large town in the USA will have an injector shop.
Find the source of the water intrusion .... Then use something such as Stanadyne etc. that will have the correct chemicals so that if your tank water continues it won't be ACIDIC ànd thus cause such a corrosive 'lockup' of the rack and pintles, etc.

 

[wbmiller3]

Thanks

 

[admiral 31]

Sorry to bring up an 8 year old thread,
but I have exactly the same problems with a seized injector pump on my Yanmar 3GM in that it runs at full throttle & the only way to stop ir running is to block the air intake (with a Sponge)
I wonder if Crosswind still has the pdf manual & if he could send it to me please
bearing in mind that he has not been seen on here since 2015

 

[heritage]

This forum has a huge list of various manuals for download. Click on "Boat Info" then click on "Downloads". You will find the 3gm service manual there.