Yanmar 3gm30

[yelbis]

Does anyone know if these engines have a common fault of slight leak of diesel or what to look for. Under engine for a couple of hours I would suggest i loose a desert spoon full into the bilge under the engine. It is not an awful amount but mixed with the heat and leaving until the next day the smell is quite evident. I have looked at the lift pump and injectors and although wet to touch would not suggest this to be the cause.

Thanks

 

[peter2407]

Mine is drizabone...

I have this engine and have to say it is dry as a bone, no leaks. Would suggest that you go through a process of elimination, starting with completely cleaning the engine bay and then putting down kitchen towel to see if there are any drips. Have you checked the tightness of everything? How close is the primary fuel filter to the engine? Any signs of leaks on pipes etc?

 

[earlybird]

The injector spill pipe has a rubber hose connection, about 1/2 in. OD. Check if this is cracked.

 

[misterg]

wet to touch

= leak.

A useful technique is to clean everything up, then go round and wipe each joint / bleed-screw with a dry piece of coloured toilet paper. Even small diesel leaks become apparent by a dark damp patch on the paper.

I think you have the same Yanmar fuel filter as the smaller 1GM and 2GM series engines. Stripping the threads on the bleed screw in the top of this seems to be a popular pass-time. Also, Yanmar make the filter housing very difficult to tighten up properly (the serrated ring bottoms on its threads at about the same time as the std. 'O-ring' seats). Several (including me) have fitted a larger diameter 'O-ring' between the housing and the head to cure persistent leaks.

Going by other Yanmars, the engine should be squeaky-clean normally.

Andy

 

[affinite]

Replace the copper washers around the fuel filter and make sure they are nice and tight (but do not overtighten ) Worked for me on my 3gm30 (run your finger around the connections and under the filter housing to confirm)

 

[Spyro]

Replace the copper washers around the fuel filter and make sure they are nice and tight (but do not overtighten ) Worked for me on my 3gm30 (run your finger around the connections and under the filter housing to confirm)

If would make sure they were leaking before doing that.
If it's not broke don't fix it

As other have said, clean it all off, use a solvent or degreaser, dry it all out then run the engine and watch for any damp patches or drips. I havea 2gm20 no leaks or smell.

 

[yelbis]

Thanks for all the replies. Misterg please elaborate on the over sized 'o-ring' Am I correct that this would still have the original internal diameter with an oversized outer diameter? I am unsure of the material but shall take a look this weekend.

 

[misterg]

Thanks for all the replies. Misterg please elaborate on the over sized 'o-ring' Am I correct that this would still have the original internal diameter with an oversized outer diameter? I am unsure of the material but shall take a look this weekend.

I've tried to find a picture on the web, but can't, so 1000 words will be required:

I'm talking about fuel filters that look like this:

The filter bowl fits inside the filter head. The seal between the filter bowl and the head is achieved by trapping an o-ring between the lower face of the filter head and the top face of a ridge a few mm down the side of the bowl - there isn't a groove that the o-ring sits in. The serrated ring screws onto the filter head and bears on the bottom face of that ridge to apply pressure to the o-ring.

As time goes by, it can become difficult to get the o-ring to seal, even if you renew it (as recommended by Yanmar). There's a limit to how much you can tighten the serrated ring because it bottoms on its threads very quickly.

It's obvious when you change the filter - just difficult to describe.

Replacing the stock ~1mm thick o-ring with a ~2mm thick one (same ID) gives the seal a new lease of life.

There's a thread on here about it somewhere - related to starting problems caused by air leaking into the filter by this route when the engine has been standing.

I wouldn't do it unless you have a leak here that can't be cured otherwise. I believe nitrile rubber is OK.

Andy

 

[vyv_cox]

Adding a little to what Misterg has posted, I read not that long ago that some of these filters have a minor machining fault. Apparently the collar runs out of thread before it has pulled the bowl up tight against its seat. So the same fault that he describes but built in, rather than developing over time. The larger O-ring will solve this but I managed to seal mine last time with a light smear of instant gasket around the O-ring.

 

[yelbis]

Sounds like I should investigate the filter first following the tissue procedure. Do Yanmar sell the upgraded seal as its sounds like they should do!

On another matter, I have a heat plug toggle switch on the cockpit panel, it appears that it does not work. Do these engines have a heat plug or do they require just a prime by using the throttle to start.

Thanks

 

[trevora]

I finally traced the persistent diesel leak on my 3GM30 to one of the two banjo connectors at the top of the filter (different to the one shown) if you have this type it's worth checking.

The problem arises if either is angled directly downwards - the crimped banjo to pipe connector fouls the filter locking ring & does not sit perfectly flat. If it's not possible to angle the pipe outwards slightly Yanmar apparently supply a double thickness copper washer to compensate, or you could probably just use two.

My 10 year old engine does not have heater plugs, I don't know if that's general though.

 

[HMG]

3 gm leak

Saw a chap suggesting instant gasket. Dont use anywhere near fuel lines it is washed into the system. If you want to add a measure of sealing use grease. The injectors themselves leak in time and dribble down the engine case. These injectors can be rebuilt but they do because of their design wear so if your going long distance off shore get serice exchange units if they are leaking.

 

[Spyro]

Sounds like I should investigate the filter first following the tissue procedure. Do Yanmar sell the upgraded seal as its sounds like they should do!

On another matter, I have a heat plug toggle switch on the cockpit panel, it appears that it does not work. Do these engines have a heat plug or do they require just a prime by using the throttle to start.

Thanks

No heat plug on the 2gm20, manual advises full throttle to start, I never find I need full throttle though 3/4 is enough when cold and throttle back as soon as she fires up. She will start with no throttle when warm.

 

[vyv_cox]

Saw a chap suggesting instant gasket. Dont use anywhere near fuel lines it is washed into the system.

I said a smear, not a huge dollop. Wait to let it cure before running and it's fine.

 

[HMG]

3 gm leak

Guys I dont want to get into an argument over sealant but having spent over 40 years in this industry and have earn t more than enough money from smears of sealant on fuel lines I thought it helpful to warn you all as to the consequent. If an O ring will not seal with out goo there is a fault fix the fault.

 

[rob2]

The GM series do not have heater plugs. Full throttle when the engine is stopped allows extra movement of the fuel rack for cold starting. This extra movement is not available once the engine fires.

Rob.

 

[Spyro]

The GM series do not have heater plugs. Full throttle when the engine is stopped allows extra movement of the fuel rack for cold starting. This extra movement is not available once the engine fires.

Rob.

Lost me there. Could you explain further?

 

[yelbis]

Cold start with throttle disengaged, big puff of smoke as she fires up, then straight to neutral. Started first time. I shall leave the toggle switch alone then!!

 

[eagleswing]

diesel in the bilge...

hmmm, diesel in the bilge but no erratic running of the engine ?? if a fuel supply hose from 1st primary filter right after the fuel tank, in to the secondary on engine filter was leaking fuel out, would one not expect air to be getting in ? which would eventually cause erratic running...

things to check in addition to excellent suggestions above :


1) mechanics who don't know yanmars often don't replace the copper 'crush washers' when working on the fuel system as yanmar emphatically recommends...

2) does the primary RACOR-style filter have a drainbolt at its bottom, and is there leakage out of the drain bolt ?

3) check the integrity of the fuel tank particularly the fuel return line and fuel input port. i once saw a fuel tank that had been beautifully painted on the outside, but the old metal tank had sprung a very slow drip leak that was puting raw diesel into the bilge.

tell us what you find, for my curiosity..

 

[Blueboatman]

Wot MisterG and Trevora said.

New copper washers whenever you disturb the fuel lines, new/thicker o ring, and 'that' tightly fitted banjo'd flexible link at the secondary filter can be remade by any hydraulic shop on your nearest industrial unit for a tenner or less...

There is no preheat on GM series. I quite like to wind the engine over with cylinders decompressed until the oil warning buzzer goes off, then do a 'normal' start, if it has been standing unused for more than a few days. Possibly the motor will last longer this way. Continuous cranking without firing would of course overfill the exhaust with seawater.