Yanmar 3GM30F ran then stopped

[robertmfranklin]

I have tried to locate this exact subject, but there are so many engine threads I have not been able to zero in on and aswer to my question. So, I'm starting another thread. Sorry.

My 3GM30F has run flawlessly for 15 years with embarassingly little maintenance. I have changed the single Raycor Filter and the engine fuel filter on occasions. But I have relied on the good running experience to do little else. Changed the oil. Kept the fuel tank full.

Yesterday the engine started up immediately as it always does. It ran for 5 minutes then stopped and nothing I could do for the next 8 hours of concentratioin would get it going. Not even a cough. It turns over just fine. But will not start.

I reasearched as best as I could from a hotspot on the boat and came to the conclusion it is likely the fuel feed pump. I ordered one. But now after reaching a bit more on CF, I am not so sure. The pump arries Saturday. It is now Thursday night. My wife and I have been planning a cruise (Cape Cod) for months and the engine stopped dead, just as I was about to slip the mooring line in Boston Harbor. Five seconds from a real problem as the wind was howling Wednesday morning. So I sat at the mooring for the next 8 hours doing nothing except trying to diagnose the problem.

Finally, I decided it must be the fuel lift pump. This was based on reading something on line that said if the fuel lift pump fails to operate properly the engine will stop and will nto be able to be re-started.

That symptom matches my situation exactly.

After trying to start the engine, I removed the fuel filter which is just after the fuel lift pump and just before the injector pump. The bowl was mostly empty and only filled partially after 30 seconds of cranking. Thirty second is a long time and I didn't dare do longer. I bled the three injectors ... nuts on top ... no air exited, no fuel. Even after 30 second the fuel filter bowl was only 1/3 filled at most. I ordered the fuel lift and I am waiting for Saturday, two days from now.

However, in the mean time I am OCD and something on CF has made me waiver in my hope that it is the fuel lifter.

CF participats seems to suggest that the fuel lift device is critical, more so, when it is necessary to bring the fuel up from below the engine. That makes sense, but the implication is that it might not be so important when the conditions are as they are on my P36-1, that is, the Diesel fuel tank is above the engine. The suggestion is that gravity will allow fuel from the main tank to fill the fuel filter bow and from there the rest of the fuel supply trajectory. That doesn't make a whole lot of sense to me, but part of my skepticism may be due to the fact that down deep I want it to be the fuel lift pump, because I know where it is an have the skill to remove it and replace it.

Now having read Cruiser's Forum, I am not so sure. This is the source of the no start condition. No Start!. Good crank, but not so much as a hearty cough.

What else could it be.

I've tried bleading the injectors (am I doint that correctly), but if there is little or no fuel in the bowl where the engine filter is located, how is bleeding like that going to have any positive effect.

When I removed the fuel lift pump and gave the linkage a good push up and down, I do get a stong diagram response, with a very little, but still noticeable, suction on one side.

I am a little desperate. My marriage depends on my being able to fix this problem.

[Stu Jackson]

1. Fuel Starvation and The Obscure Check Ball Valve
https://c34.org/bbs/index.php/topic,10681.0.html
and
https://forums.sailboatowners.com/th...l%20Starvation




2. Do you have a screen on the fuel pickup IN your fuel tank?


3. Is your lift pump before or after the Racor? Did you clean the filter on the lift pump (if it has one)?

[JimsCAL]

When blèeding the fuel system by pushing the lever on the lift pump, does fuel and air come out of the bleed screws? If so that would indicate the lift pump is working. Note that in addition to the one on the engine filter there is one on the injection pump that is not well documented.

[chris mac]

Just as another (easy) thing to check, as it's Something I once did on my 3gm30f
Double check your kill lever isn't partially out. If it's partially engaged, you will get crank but no cough.
As for fuel, if the pick up line from the tank gets plugged, it will create a vacuum in the racor and kill the engine. As soon as you open the racor the vacuum goes away and the debris may fall away but you will now need to syphon or pump to get fuel flowing. Once it's flowing, gravity will feed the whole system. Open the final bleed screw before the injector. It's behind one of the coolant hoses, but easily reached. Once fuel comes out with no air bubbles, close it and try to start.
If you can't get fuel flowing from the tank, take apart the fuel line shut off(probably) at the top of the tank. Or the first fuel line fitting after the tank. That's where a piece of debris will usually get stuck.
If that ends up being the issue, I recommend getting the fuel polished as well.
Good luck

[Tin Tin]

Just so I understand you mention a fuel "feed" pump and a fuel "lift" pump. I presume the lift pump is electric? If so, easy to test.

[robertmfranklin]

To Stu: Thank you for your suggestions 1,2 & 3. I don't think 1 or 2 can apply because of the suddenness of the running engine shut down. I would expect some coughing and finally a stop. As to no. 3. My system is pretty routine. Diesel Tank, shut off before Raycor. Raycor. Lift pump. Fuel Filter. Injection pump.

[robertmfranklin]

General reply info.
No screen in tank
No fuel or air when pumpint lever.
"Fuel Lift Pump", "Fuel pump". Fuel Feed Pump All the same thing. Brings fuel to the injection pump.
Chance of absolute clogging in the line between Tank and Injector pump? Slight, also keep in mind the shut down wat 100 percent and no restart at all.
New filter in the fuel bowl following the lift pump. The old filter looked like new, suggesting the fuel does not need to be "polished".
Lift pump is mechanical not electric. It runs off a cam on the crank shaft.
Chris Mac: Gravity may move the fuel from the Diesel tank to the injector pump but not if a check valve in the lift pump impedes or prevents entirely this gravity flow.
Chris Mac: First I've heard of a "final bleed screw" before the injector? I'll look for this. When you say "before the injector," do you mean after the injector pump and before the three injectors on my 3GM30F.

[chris mac]

Chris Mac: Gravity may move the fuel from the Diesel tank to the injector pump but not if a check valve in the lift pump impedes or prevents entirely this gravity flow.

Chris Mac: First I've heard of a "final bleed screw" before the injector? I'll look for this. When you say "before the injector," do you mean after the injector pump and before the three injectors on my 3GM30F.

Correct, the gravity feed only feeds to the injector. But if you remove all air leading to the injector, then life becomes easier.
The pic I included shows the final bleed screw(prior to injector). follow the fuel line from the filter towards the injector. It's a Phillips head screw, also a socket, I think 8mm but not 100%sure. Use a socket, the Phillips strip out easily because of the awkward position. It's behind the coolant hose.

As long as fuel is flowing from the tank to the inline filter,and tank is higher than the engine, Crack this bleed screw and that bleeds the whole low pressure side.
If no fuel flows, then the fuel line is probably plugged upstream somewhere. My guess is the first fitting, elbow, shut off valve, ect, after the tank. The fuel line is so tiny on this engine and the fittings are inside creating a choke point. Mine has clogged here without any deebris in the filtr before.

[AA3JY]

Fuel polished and tank clean??
Pick up tube and fuel line not impeded?

[JimsCAL]

A mostly empty engine fuel filter and it not filling when cranking sure points to fuel starvation. Most likely either the lift pump or a blockage in the system. Don't bother bleeding until you get good flow and the filter is full. And be careful about cranking with the raw water seacock open as water can back up from the exhaust into the engine. Best to leave it closed until the engine starts.