3GMF Fuel Flow/Bleed

[Dave19957]

I have a 1983 Hunter 34, Yanmar 3GMF, with a Racor fuel filter. I had no problems with fuel/engine run UNTIL I pulled the old (can't remember last time I changed it) filter, and put in a new one in earlier this week.

I did not remember (or never realized) that I should have cut off tank fuel flow first, and made sure I topped off the bowl before putting the cover back on. :naughty:

Yesterday, I started the engine, got 4 of 5 dock lines off and was backing when she died...

After much noodling, and some forum search here, I did these things:

1. Filled the Racor bowl and the smaller fuel/filter bowl with diesel fuel. Tried to pump the little and well hidden lever to try to get fuel to flow up to the injector nut with I opened... nothing.

2. Opened the nut at the small fuel bowl (on the side) because there is no way to get a screw driver tip on the bleed screw on top because the fuel line runs 1/4 of the way over the surface area and couldn't get a good tip/screw line-up.

3. Tried cranking engine interimittently to try to get some fuel flowing - nothing.

4. Bought an outboard squeezy ball from West Marine, and installed that at the Racor... Squeezed it (injector nut still open) and nothing flowing out... except out of the squeeze ball.

5. Opened up the nut at the small filter again, and fuel game out.

Sooooo, I'm getting fuel to the small fuel filter, but not beyond... that I can tell. "Something" is restricting flow, right? I thought that maybe I should go back to the boat and try to:

1. Push the small primer lever in the down position while at the same time squeezing the squeeze ball... Does it open up a diaphram that's otherwise closed in the "up" position (not an engineer, but it's what my brain came up with).

2. Does the throttle position matter? It's in the up/neutral position.

3. Since the small fuel filter is very clean - I'm doubting that anything got to the up-stream side of the line heading toward the injector... but I guess that could be possible - don't know that I dare messin' with that!

4. Could the small pump have coincidentally failed in addition to my BAD on the fuel filter change?

I'd appreciate any suggestions before I call for a mechanic... I really do try to keep things running myself - this time I shot myself in the foot though... Thanks in advance, Dave.

 

[kloudie1]

You probably have a big air bubble in the low pressure line heading to the injection pump and more air in the high pressure lines.. first.. close the water inlet line so that you don't get water into the engine from the exhaust.. Next.. find the pump bleed screw on top of the injection pump (it will probably look like a plug with a phillips headed screw in the middle; it can be opened with a wrench but be careful not to strip it). If you are getting flow out of the squeeze bulb, pump that until only diesel comes out of the pump bleed screw.. Close the screw while squeezing gently so absolutely no air can get into the system. Next.. pull the decompression levers and crack one of the injector high pressure lines at the injector. This is the big nut on the side with the tube going into the middle and NOT the little top fitting.. Throttle forward..Spin the engine with the starter a few seconds until diesel comes out then close the nut.. do that on the other two and then open the sea water valve , close the decompression levers.. she should fire right up.You can leave the bulb in the system to make this job easier.. The little lever operates the lift pump diaphragm .. but that diaphragm is also operated by the engine camshaft.. IF the cam is pushing the diaphragm up, you will not be able to get the lever to pump.. until you turn the engineso that the cam is no longer pushing on the diaphragm. When it doesn't pump, turn the crankshaft 90 degrees and try.. then another 90 if it still doesn't work, and so on.. you shouldn't have to turn it more than one turn to get the pump lever to work, since the cam turns at half engine speed.

 

[Dave19957]

Thanks for the response Claude! I'm not clear on the decompression levers... Where are they located and when you say "pull" is this something I do with my hand, or a wrench/other tool? Thanks again!

 

[Ivan]

Similar but much simpler:

I agree with Dave that you probably have sucked air into the system. But there is a much simpler solution that worked well for me when I had an air leak and the engine died the same way yours did:

Close the sea water through-hull valve. Open the throttle ALL THE WAY, with the transmission in neutral, and KEEP IT OPEN. Hit the starter and crank NON-STOP until she starts. In my case that only took about 15-20 seconds. The engine may slowly come to life but will eventually run normally. Gradually back off on the throttle. Then open the thru-hull valve and you are on your way. No need to loosen any fittings or connections whatsoever.

If you have a low battery problem and can't wait for the charger you can minimize the load on the battery by releasing the compression from the cylinders and cranking for 20 seconds minimum, then engage the compression levers again, and she should start normally. (Don't forget to shut the sea water through-hull before you crank unless you want hugely expensive repairs).

 

[navigator97]

Daave,

The decompression levers are on the top of the engine, one behind the other, one for each cylinder. They just rotate up from front then away from you (if you are at the forward end of the engine). When done with the bleeding process (turning the engine over without firing it), just close all 3 levers.

 

[kloudie1]

Decompression Levers

They are the three little levers on the port side of the valve cover, the side toward the injectors. When you pull them aft, they open the valves so the engine does not have any compression and the starter can spin the engine more easily. When done, youcan just flip them back forward..
Ohhhh i am assuming that you have the Yanmar 3 GMF and not the Westerbeke that was put in some boats..
Ivan, the earlier model Yanmars do not "self bleed" as your engine does..

 

[Dave19957]

You guys rock! I did learn more than I knew for sure... and I didn't have to call a mechanic. I tried to get at that bleed screw again at the top of the pump, but without a special tool, there's no way for me to get around the fuel line that runs right on top/over my screw.

So I flipped the compression levers up and loosened the injector bolt Claude directed me to... and used the method Ivan described. I put a piece of paper towel under the nut so I could see if fuel came out from my full throttle cranking... and when I took a look - it had!

I had to monkey a bit more than Ivan suggested, but kept faith and after a bit got the engine to run. After the roughness worked its way out I let it run a few minutes, and the put it in gear and ran it that way for 30 mins. Seems to have done the trick! I am finding that fuel leaks from the squeezy ball, and I will be removing it and putting a hose barb in the two lines to make it one again... but keep the ball in a tool box just in case. I hope when I do that I don't have another problem to bleed, but I'll shut off the tank line first, and if I do, I'll know how to address it, thanks to your collective assistance.

One question/observation - could be another problem, you tell me. When I lifted up the forward compression lever, it did not have the resistance/clicking sound I felt/heard in the middle and aft levers. It seemed pretty limp/floppy to me. I'm guessing this isn't normal, but that's just a guess since you guys just schooled me up on these levers today.

Thanks again for the help, and in advance for any thought you may have on the compression lever. Dave.

 

[kloudie1]

Ya welcome, Dave.. Lots of collective wisdom here on the site.. good to have input from a few members..
The one lever is probably OK and was acting that way because the camshaft position had lifted the valve anyway.. one of the three randomly will usually act that way when the engine stops.. As long as you could spin it freely and it fired when ya turned the compression back on, it is working fine.

 

[Dave19957]

Relieved to hear that... Thanks again Claude! Fired it up this evening just to be sure and she started right up - great feeling.

 

[Dan Johnson]

Dave...

Forget the phillips head screw driver for the filter bleed screw. Go to Sears or some other tool source and buy yourself 12mm and 10mm combination wrenches. The 12mm fits the bleeders on top of the yannie filter and the 10mm fits the bleed screw at the high pressure pump. That one's hidden by the water hose at the front upper left on the engine, facing it. It's hard to reach (feel around for it atop the HP pump) and there's only a little bit of room to move the wrench inside the hose loop so one of the new box ratcheting wrenches might be the better solution. Once you've bled the HP pump, it should fire up right away, but may need the compression lever assist.

Further, get a supply of the brass washers that go under the bleed screws. The don't like to be tightened down on more than once or twice when bleeding before they start leaking (like the old VW oil pan drain plug washers).

I also use a squeeze bulb to prime and bleed the fuel system (and think it needs replacement as it doesn't seem to pump any more after about four years in use). Be sure yours is rated for both gas and diesel. Also, the little pump (the knurled knob thingie) on top of the Racor is easier to use than the lift pump lever, if you can reach it easily.

When the compression levers are rotated, they push down on a valve, opening it slightly. The one that you felt as floppy was probably engaging a valve that was on its way open or closed already, and not shut. When I use mine, I flip just two so that one cylinder can fire. The others seem to shake back closed on their own usually once the engine starts to fire on the one cylinder.

Also, you also don't want to close the fuel line valve at the tank when you are trying to bleed the engine. If you do, no fresh fuel can get through to replace that which you have bleed out.

Good luck and enjoy this great boat!

 

[Dave19957]

Thanks Dan! I'll take a look at that screw again - I do have metric wrenches, but either not the right size for it, or it wasn't a screw head that was also shaped like a nut... Mine isn't a phillips slotted screw, it's a flat screw... So I raised my eyebrow at that, and it's not being accessible because of the fuel line running too close, and over the top of the screw.

I had thought about those banjo washers... and I'm gonna get a set. I seem to remember that they're not all the same size... but my yard parts department guy is good, and we'll sort that out.

I'm adding your notes to my folder on this subject that I'm keeping on the boat... Just in case I can't remember it all next time! Thanks again! Dave.