Diesel Fuel Leak

Feb 18, 2023
6
Hunter 34 Lake Hartwell
I have a Yanmar 3GM in a '84 Hunter 34. There is a fair sized leak from this location and I hoping someone may be able to identify the fix. Drips occur about every 5 seconds when running.
fuel leak yanmar 3gm.jpg
 
Feb 10, 2004
4,065
Hunter 40.5 Warwick, RI
This looks like the engine-mounted secondary fuel filter. The fuel lines connected to it are banjo fittings and they use a crush-able copper washer for sealing.

My first attempt would be to tighten the attaching bolt on the fitting that is leaking- either the input or the output. If that doesn't stop the leak, then remove the bolt from the fitting and replace the copper washer(s) and re-attach.

Obtain the copper washers from Yanmar- they may be a special size and type of copper.

In a pinch, you can heat the washers in a flame until glowing red and then drop into water. This will remove the temper from the copper and make it soft again.

Here is a video on the process-
 
Nov 21, 2012
677
Yamaha 33 Port Ludlow, WA
I have the same problem and it's next up on the project list to finish off.

I've tightened the secondary filter bowl. That helped. Tightened the banjo fittings. That also helped. However, the leak persists so next step is to replace the crush washers and bowl o-ring. If that doesn't work, I'll replace the banjo fitting.

@Ralph Johnstone, you wouldn't have a part number for the new style washers would you?
 

RoyS

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Jun 3, 2012
1,742
Hunter 33 Steamboat Wharf, Hull, MA
On the aluminum casting of the fuel filter assembly it is very easy to strip the threads.
 
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Nov 21, 2012
677
Yamaha 33 Port Ludlow, WA
On the aluminum casting of the fuel filter assembly it is very easy to strip the threads.
Thanks for the reminder. No more tightening - time to replace the o-ring. It's also easy to get the o-ring twisted - which is what I think happened last time I checked the filter, causing the leak.
 
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Feb 18, 2023
6
Hunter 34 Lake Hartwell
Thanks for the speed, accuracy, and knowledge. Getting back into sailing and will likely see you all here again soon.
 
Jan 4, 2006
6,960
Hunter 310 West Vancouver, B.C.
@Ralph Johnstone, you wouldn't have a part number for the new style washers would you?
All comes to he who waits.

I just completed replacing all of the fuel lines in the engine compartment. After 24 years, the 1/4" rubber hoses were getting a little hard and it was time for them to go. After completing the job, it was time to restock my supply of gaskets and I picked them up from the supplier this last Friday.

I'm presuming you are looking for the banjo gaskets ?

This is the part number for the new rubber insert washers which shows on the envelope :

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The parts catalogue shows the plain soft copper washer as 22190-120002

And this is what you get for $5.39 CAN each :

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The metal washer is steel (magnetic) and the raised rubber is a hard material which compresses. Do not overly tighten the fitting as the steel washer does not crush. You will often get someone in sales who cannot find that number as it is a special issue with a "special price."

time to replace the o-ring. It's also easy to get the o-ring twisted - which is what I think happened last time I checked the filter, causing the leak.
It's definitely not an "O" ring in there but either a soft copper washer or a washer with a rubber insert as shown above. If there is an "O" ring in the banjo fitting, that is why it's leaking.
 
Nov 21, 2012
677
Yamaha 33 Port Ludlow, WA
Thanks for the extensive writeup. The o-ring is in the secondary filter (fuel strainer). P/N 24341-000440.
 
Last edited:
Jan 4, 2006
6,960
Hunter 310 West Vancouver, B.C.
The o-ring is in the secondary filter (fuel strainer). P/N 24341-000440.
Ah yes, who could ever forget P/N 24341-000440 ?

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Remove the "O" ring and check for damage. If it's undamaged and good to go back again, lubricate it with a light coat of petroleum grease. This prevents grabbing and twisting as you tighten it. Actually, all "O" rings should have a light coating of a suitable lubricant when installed. Just maybe not petroleum grease for a potable water faucet "O" ring.
 
Nov 21, 2012
677
Yamaha 33 Port Ludlow, WA
I might have nicked the o-ring the last time I checked the filter. The o-ring is the same on the 3GM30F. The filter on the -YEU is in a much better location. There are times when I wish endless torment on the Yamaha engineer who shoehorned the engine into place with such limited access. I had to install a mirror just to check the oil. Finding the leak has been challenging - and risky to stick a camera back there while the engine is running.

It looks like @Rkelly44 has an access port. I will do that someday, but it will require replumbing the water filter and pump. In other words, not urgent.
 
Jan 4, 2006
6,960
Hunter 310 West Vancouver, B.C.
I like to bitch about getting at my enginebut actually it has one of the better accesses I've seen. Entirely uncovered when open but a little close to the walls for working.

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