Bleeding Yanmar Injectors

[mnmpizza]

I just want to be sure, as I’ve seen both options suggested. After bleeding the secondary filter; then the high pressure pump inlet; do I bleed the injectors at the Red or Yellow circled area? I’m betting the Red?
And, what do I need to be aware of when loosening and tightening that fitting?
Also, Any truth to choosing the injector furthest from the pump? Or, just do them all?
Thank you! Shannon

 

[kloudie1]

Red circled area, Shannon.. The high pressure line from the HP pump.. You are correct.. when ya open it, it will only require usually only a flat or half a flat of the nut. Bleeding there is done with the engine spinning. decompress lever on and throttle open. If ya crank more than a minute, water will back up into the engine so best to either remove the water hose at the elbow or remove the sea water drive belt while ya bleed. Close the fitting before stopping the spinning to avoid any possibility of air getting back in.. Not necessary to bleed any one preferentially since they are independent at that point.

 

[BigEasy]

Looks good Shannon! Was it rebuilt, remanufactured, new?

 

[mnmpizza]

Looks good Shannon! Was it rebuilt, remanufactured, new?

sorry, not my 3gm... should have stayed that!

 

[mnmpizza]

Red circled area, Shannon..

Thanks. I’ve been chasing a fuel starving situation on my H34. I went ahead and added a priming bulb before my primary racor to help with bleeding. I have also pumped it; marked the needle on my vacuum gauge (of course it had pressure and not vacuum); then waited a week with no evidence of leaking. The only item I haven’t ever bled is the injectors. So wanted to give it a try. With the positive pressure in the fuel line now, The engine starts easily when cold and runs very smoothly.

Im thinking I may have found my problem before installing the bulb. I’m thinking my racor lid was not sealed properly and thus the lift pump sucked it dry. The racor is mounted about 4” above the injectors and 8-12” above the lift pump.

 

[kloudie1]

Sounds like you've found it..
If the engine runs, you can bleed it when running by cracking that fitting and letting it squirt a little bit (2-3 seconds) to make sure that all air is out. That cylinder will not fire when ya crack the fitting, but it will restart as soon as you re-tighten the nut..

 

[HMT2]

I have a 2gm and I usually don’t have to bleed the injectors.

 

[Alan Gomes]

I have a 2gm and I usually don’t have to bleed the injectors.

Same with my 1GM.

 

[Benny17441]

Is the tank fuel shutoff valve higher or lower than the Racor? Usually fuel should flow by gravity alone to the Racor. Last time my Racor got suck dry of fuel was due to a blockage in the screen of the pick up tube in the tank.

 

[NYSail]

Never had to bleed my 3HM35f at injectors but yes the high pressure side is where you do it from. Have plenty of paper towels ready

Good luck

 

[mnmpizza]

Is the tank fuel shutoff valve higher or lower than the Racor? Usually fuel should flow by gravity alone to the Racor. Last time my Racor got suck dry of fuel was due to a blockage in the screen of the pick up tube in the tank.

My racor is probably about 12" above the tank shutoff valve... So, I definitely need 'suction' to get fuel into the racor. Like I had mentioned earlier: I believe I had replaced the racor lid without looking at the associated O-ring - - as a result, the O-ring was not seated properly and caused a loss of suction - - thus causing my engine to starve of fuel...
In the process of bleeding, I noticed my 1-yr old lift pump wasn't grabbing any fuel. So I started tracing backward. Then, I noticed the O-ring on the racor... While doing research, I stumbled upon the "fuel bulb" method and purchased and installed it before the Racor. This has made bleeding so much easier. I utilized my vacuum gauge [in reverse] and pressurized the racor-to-the-high-pressure - - and noticed no fuel pressure loss. So, I know I have a sealed system which should be able to create the vacuum I need. Just wanted to bleed the injectors, because I never have...

 

[mnmpizza]

Sounds like you've found it..
If the engine runs, you can bleed it when running by cracking that fitting and letting it squirt a little bit (2-3 seconds) to make sure that all air is out. That cylinder will not fire when ya crack the fitting, but it will restart as soon as you re-tighten the nut..

I guess the 64K question is: If the engine runs/starts fine after bleeding all the way to the hi-pressure pump - - why might I need to bleed the injectors?? I'm sure I ran my engine out of fuel before I bled to the HPP.

 

[ggrizzard]

I don't think you do. Whatever air is at the injectors should be pushed out by the fuel
in the line, then into the cylinder and out the exhaust valve.

 

[kloudie1]

The smallest itsy bitsy little bubble in the line from the HP pump to the injector will affect the timing just a smidge as the bubble has to compress before the injector sees enough pressure to open.. Not super critical, just something that should be done for smooth running ..
The newer engines are self bleeding but our old ones are not exactly..

 

[kloudie1]

They will eventually clear through the bypass line, but it may take some hours.. The injector flow rates are tiny...

 

[Ken13559]

I believe the yellow and red circle is the return line to tank. I don't remember having need to bleed injectors. Just the secondary filter will do. Yours may differ.

Ken Y

 

[2Sheets2TheWind]

I came upon this thread on a Google search and I have something similar but not the same. Hopefully this will reach some of you who commented two years ago. I have good compression, but the engine doesn't turn over. Fuel is good but I replaced the Racor primary filter and secondary filter on my Yanmar 3GMD for good measure (both were clean). I have replaced the mechanical low pressure lift pump near the tank (the tank is lower than the engine and filters but the old lift pump was not original--a PO installed it about 10 years after the boat was manufactured). I've bled the system at the secondary fuel filter with the bleed screw and also the bleed screw on the high pressure pump numerous times. Both appear to be good. I replaced the coppers on the banjos at the thumb actuated pump where the fuel pipe goes to the secondary filter, as well as the coppers there, and then the coppers at the high pressure fuel pump. After I bled the high pressure pump and the secondary fuel filter, I opened the screws again and fuel spurted out so it was primed, and of course I bled them again. Can/should I bleed the injectors at their bleed points (where the red circles are on the original post) without having the engine operating (since I can't get it to turn over)? I have a small electrical push button pump prior to the Racor--installed it a few years ago to make bleeding easier. Replaced all the fuel lines a couple of years ago. The lift pump actuates on demand but I tested it by linking it to the battery for continuous power and it pumped well. I cannot find any place the air is getting into the system, but the engine doesn't turn over. BTW, I have the raw water cooling sea cock closed so no water is getting into the engine oil. Thanks.

 

[heritage]

I know that fuel can be pushed past the high pressure pump with the engine off. I have done that with a small electric pump prior to the racor filter and observed fuel coming out of the fuel return line. But I'm not sure if the fuel was going to both injectors. The high pressure pump may block the flow to a cylinder depending on the location of the cam rotation. Why don't you try turning your pump on and try opening each injector inlet and see if the fuel flows and let us know what happens.

 

[SycloneDriver]

How long has it been since the engine last ran?
What lead up to this issue?
How do you know the compression is good?

Note. If the starter motor spins the crankshaft of the engine, than it is "turning over."

 

[2Sheets2TheWind]

How long has it been since the engine last ran?
What lead up to this issue?
How do you know the compression is good?

Note. If the starter motor spins the crankshaft of the engine, than it is "turning over."

Good questions and I should have given the symptoms. A month or more ago while we were motoring out to the Bay, the engine shut down. There was a huge oil leak. We were towed back in, I cleaned the mess up, and discovered the oil line on the port side had rusted over the years and sprung a leak. That part is under the starter and not inspectable visually without removing the starter or using a mirror. Someone I contacted said it is a common problem on the older engines over time (I know we were lucky and the engine did not seize up). I replaced the oil line with a new one, refilled it with oil, and voila, it cranked up. I ran it in the slip several times--mostly at idle but a few times under load. No issues. The next journey, the engine shut down after about 5 minutes of motoring out of the marina and to the Bay at about 1500-1800rpm. We sailed back in, and I cranked it again and it started. We let it run for a while, but it again stopped and I haven't gotten it restarted again. I did some internet searching which led me to believe there is fuel starvation somewhere. A video I found was from a Mack Boring mechanic teaching a class for sailboat owners with small aux engines on simple maintenance. He made the statement that a marine diesel engine will run with the fuel it has in the system for 25 minutes or more at idle. When I replaced the line I had to loosen the fuel line from the finger actuated pump to the filter on the port side. I replaced the crush coppers on those two banjo bolts to insure there was no gaps. I'm assuming there is good compression because it sounds like it's going to start and the crankshaft does rotate--it just never engages. I have not tried with the throttle engaged, and as I write this, I probably should have tried that. Thanks.