Yanmar 3GM30F tough starting (runs well)

[mermike]

I'll add my recommendation to Syclone's. My 3GM30F was really hard to start until I redid the starting circuit. I went from 6 AWG cable and the battery 8' from the starter, to 2/0 cable and 3' away. What a difference. Temps were recently in the high 30's and I hadn't been to the boat in over a month. She fired right up. I feel like a kid at Christmas every time I start the motor now.

 

[John T1594]

Black smoke (unburned fuel) at WOT can also be a fouled propeller or one that is the wrong one for your engine and tranny.

 

[Benny17441]

Raise compression. Hard starting is a result of the engine not building adequate compression to reach the flash point of the fuel in a normal number of cranking revolutions. The culprit could be in the valve seats or worn piston rings and cylinder ( save other issues like fuel condition, clogged intake, faulty starter or wiring, or reduced fuel flow).
In a well worn engine a cheap fix would be to increase the viscosity in the oil (once any starter cranking issues may have been resolved). Shift to 20W 50 oil and even introduce a thickening additive like STP High Mileage Oil Treatment. In those areas of extreme cold weather an engine heater can help attain adequate cranking speed.

 

[Tally Ho]

Black smoke (unburned fuel) at WOT can also be a fouled propeller or one that is the wrong one for your engine and tranny.

Thanks. Not fouled, but I don’t know if it is pitched correctly.

Greg

 

[_Milkjug_]

Alright, I'm betting on the exhaust elbow for now. Went to the boat today and water is no longer flowing over the side through the exhaust. The intake isn't clogged and impeller was just recently checked so I'm betting the water flow into the elbow is clogged. Taking a look at it this weekend.

 

[heritage]

As you can see from this image that Ralph Johnston posted, the water passageway is blocked by corrosion. The exhaust passage is fairly clear. This is what happened to my exhaust elbow and the result was overheating at higher power settings, but no problem starting. Now if the exhaust passage is restricted then I suppose you would have trouble starting and loss of power.

The problem with trying to trace down an air leak in the fuel lines is that you will rarely see any fuel leaking out at the problem areas. There is just enough fault to let the air come into the line as the fuel cools. A common culprit are the copper washers on the banjo joints. You could replace the seals with new copper washers, or what I did was use Yanmars dowty seals:
Yanmar Dowty washer bonded seal 22190-080002. They are used on the newer yanmar engines. There are 2 sizes, 8 and 12mm. The 12mm is 2219012002.

 

[Ralph Johnstone]

A common culprit are the copper washers on the banjo joints. You could replace the seals with new copper washers, or what I did was use Yanmars dowty seals:

The new washers are one thing well worth replacing on your engine. Previously when doing any work on the fuel lines, every time you slacked off a copper washer, it was an automatic replacement with a new copper washer. Now, there are a couple of washers I have removed and re-installed more than once and no leaks at all.

As far as fuel hose condition goes, check the condition inside the engine housing. It's hot in there and causes hoses to become hard. I replaced some of my fuel hoses in 2015 and the one in the engine compartment was starting to harden.

 

[chuckwayne]

Our elbow was totally coked up and producing a lot of unburned fuel smoke. ran like a watch with the new elbow. Get one of the HDI stainless exhaust elbows - beautifully engineered and manufactured, you can get the elbow, threaded coupler, and exhaust manifold for much less than just the elbow from Yanmar and they'll last forever. replacing the three parts new is much easier. Also, HDI is great to work with.

 

[RoyS]

How did u plum this in?

On the Yanmar 2QM15 there is a removable plug that is covers a port made for the Thermostart. It is just behind the intake air filter. Some Yanmars have difficulty with cold starts yet do not have glow plugs. The thermostart was the solution. If your cold engine starts well while blowing a hair dryer into the air intake then the Thermostart will work for you if you have a port in your intake manifold to accept it.

 

[RoyS]

As mermike said above your starting motor circuit may be inadequate. If I remember correctly, you should be cranking at least at 400 RPM.

 

[MikeHoncho]

I’m still trying to understand how a clogged elbow would cause as “hard to start when cold only” problem.

 

[Claude L.-Auger]

On the Yanmar 2QM15 there is a removable plug that is covers a port made for the Thermostart. It is just behind the intake air filter.

As per the attached picture made when I removed the injectors, the 3GM30F doesn't seem to have that removable plug. Do others 3GM30F owners confirm ? Incidentally, late in the Fall with colder temps and no glow-plug, in the weeks before haul-out my engine also takes a little longer to start. I crank up the fuel lever and after a few seconds it'll start and run rough spewing out black smoke for the first 5 or 6 seconds then clear up and run fine. I'm not worried about the black smoke as it is only momentarily and probably caused by the extra fuel. I have not had to blow hot air in the air intake.

 

[mnmpizza]

Could it go here?

 

[RoyS]

Could it go here?

No. That looks like a head bolt. The port on the 2QM15 is there for the specific purpose of a Thermostart, as far as I know. Looking at your 3GM30F there is no such port. Does your engine have glow plugs? From what I have discovered, diesel engines with "pre-combustion chambers" should have glow plugs to aid in starting. I do not know about your engine but the 2QM15 has pre-combustion chambers but no glow plugs. I suspect the Thermostart was applied instead. Before I found the Thermostart I had rebuilt the engine including rings, replaced the injectors, upgraded the starting motor circuit, and re-plumbed the injector return line to the fuel tank instead of the secondary filter. Nothing helped with the cold start until I found the Thermostart in a tractor supply company.

 

[frenzy13]

I had the same problem with our Cat 320 with a 3GM30F. I did everything you did. The problem turned out to be the batteries needed to be topped off. Putting the switch on both did not help. After it started it ran great, it would start easy the rest of the day. That engine has very high compression it takes a lot of power to start.

 

[Claude L.-Auger]

After looking at the service manual, these are indeed the head bolts. And the manual doesn't show that port for the Thermostart like the 2QM15 has. And the 3GM30F does not have glow plugs !

 

[mnmpizza]

After looking at the service manual, these are indeed the head bolts. And the manual doesn't show that port for the Thermostart like the 2QM15 has. And the 3GM30F does not have glow plugs !

Well, it was worth a shot

 

[SycloneDriver]

The thermostart could be installed in the air silencer, AKA air filter, housing. You will probable need to weld a nut to it to thread the thermostart into. From what I understand the smoke/vaporized fuel is extremely flammable and acts like starting fluid, but don't quote me on that.

My old boat had a Volvo Penta 2002 in it. No glow plugs. I sail in the winter as long the water isn't solid. It always stated, if I used the correct starting procedure. I read the manual!

 

[RoyS]

Thermostart's purpose is to heat the air in the intake manifold. There are videos on Youtube. What you will see is a visible flame inside the intake manifold for as long as you apply electricity to the device. It has a heating element much like an old auto cigarette lighter. Above that is a valve that drips diesel fuel when heated. That dripping fuel ignites and burns within the manifold casting. Twenty seconds works well for me. You cannot install it in the air silencer as you would set the filter element on fire.

 

[SycloneDriver]

Roy,

Many folks don't have the filter element installed in the air filter assembly anymore. My first 3 boats didn't even have air filters, just spark arrestors. So remove the filter element if installed, weld a mounting point in the neck that attaches to the motor, plumb, wire and go. I've never used a thermostart but I always thought they sounded like a simple solution. The smoke itself serves as a starting aid, not just the heat. You can run an engine on wood smoke after all.