Yanmar fuel pump leak

[sailingharry]

I have a 1998 Yanmar 4JH2E, although I believe my issue crosses many models. I have been suffering for a year now with air leaks in the fuel line.

Early on, I replaced the line between the lift pump and the injector pump with clear fuel rated tubing. This allows me to see air bubbles.

I have chased many perspective areas. All unsuccessful.

Recently, I noticed that when I run the auxiliary electric fuel pump, I have leakage at the engine lift pump. I removed the suction side line, cut off half an inch, and reinstalled it. No change.

So yesterday, I moved the suction side line from the engine lift pump directly to the injector pump, and I now use the electric pump as my primary engine pump. The engine runs like a champ!

To me, it seems I have a failure in the lift pump. It is not easy to see, will not be easy to remove, and since we are on an extended cruise, I can't take the engine out of service while I inspect, and order parts.

Has anyone ever had problems with these pumps? Is replacing the pump a likely solution? Is there something that tends to fail that can be replaced? In other words, does anyone have any wise insight into the Yanmar lift pump?

Thanks!

[Sohum]

Originally Posted by sailingharry

I have a 1998 Yanmar 4JH2E, although I believe my issue crosses many models. I have been suffering for a year now with air leaks in the fuel line.

Has anyone ever had problems with these pumps? Is replacing the pump a likely solution? Is there something that tends to fail that can be replaced? In other words, does anyone have any wise insight into the Yanmar lift pump?

Thanks!

How’s your oil? The diaphragm can fail. I haven’t replaced one myself. The remove/replace procedure should be straight forward. You replaced fuel lines, and being the primary pump, your close.

[sailingharry]

I am concerned about fuel in the crankcase. The oil level has been constant, which is reassuring. I keep thinking back to my days in the Navy, where we ran fuel oil dilution tests on a regular basis. But I don't have that equipment!

I am considering either ordering a new pump and installing it (but I hate throwing money at it), or finding a time when I can remove, inspect, replace, and then if needed order a new one (delivered to some place?) to do it all over again. Neither approach is appealing!

[bobnlesley]

As someone who's also chased Yanmar (3GM30F) air leaks at sea the advice which I'd give is:
Renew ALL the Yanmar flexible hoses - I was getting leaks at the crimped connection points where those hoses joined to the banjo unions and said leaks varied in how serious they were depending upon the precise position of/twist in the hoses. That's what had me chasing for weeks, fit the hose one way and you got air-locked in twenty minutes, a fractionally different hose position and it was good for 6-8 hours, or until the exact moment that you entered confined waters, whichever came first. It sounds like you've already changed the hose up to the lift pump, but do you have other, shorter ones between the lift pump and secondary/fine filter housing and from that to the injection pump too? It's simple enough, carefully cut off those crimped hose couplings and you can fit a new hose to the existing banjo-bolts using s/s hose clamps/jubilee clips.
Secondly, when renewing all the copper sealing washers (you may already have done so?) rather than using copper replacements, if you can get them where you are, replace them with dowty washers instead, most especially on the two bleed screws atop the secondary filter housing and on the banjo union to the injection pump (no idea why that seemed more susceptible to leakage) but preferably dowtys everywhere; they also IMO make you less likely to strip and the threads on the pumps/filter housing.
Good luck.

[Sohum]

Originally Posted by sailingharry

I am concerned about fuel in the crankcase. The oil level has been constant, which is reassuring. I keep thinking back to my days in the Navy, where we ran fuel oil dilution tests on a regular basis.
I am considering either ordering a new pump and installing it (but I hate throwing money at it), or finding a time when I can remove, inspect, replace, and then if needed order a new one (delivered to some place?) to do it all over again. Neither approach is appealing!

You say there is a fuel leak however. How much fuel are seeing? Something will need addressing. Just r/r it. There was a post recently about oil getting into fuel tank. Was a small hole/crack on diaphragm, just in the right place, oil was getting sucked in. I think u should change to pump. I don’t think it’s too “$” relative to other parts. Without eyes on it i can’t say where it’s coming thru, either the pump body or the seal. I’d change the oil too, after the pump(suspect) is replaced. It’ll be peace of mind. t I don’t want to start factoring x x amd x. But fuel, oil contamination, oil burn, oil level on dip. Can do funny things. Also diesel runaway.(pending pcv). I’m going on and on


Also. I’m replaceing fuel lines soon. And noted, all at once.

[Cruisedog]

Don't know if anyone is still looking at this thread, but here goes . . . .


I have a Yanmar 2GM20F-YEU engine installed on my Elan 333 in 2001. Reliable and easy to maintain, but the exhaust elbow weld perished, allowing hot salt water to drip unnoticed onto my fuel pump which got corroded so the manual lever became siezed.


I've just had the pump replaced and discover it leaks oil (1 X 2mm drip every 2.5 minutes = 1 litre every 1,250 hours!) from the manual level pin through the body of the pump.


So I am now asking whether this particular pump is faulty, or I got the wrong part, although it works fine in all other respects. Does anyone know the difference between two different part numbers for what look like identical pumps to me - 129301-52020 and 128270-52010?

[SY Harmony]

Originally Posted by Cruisedog

Don't know if anyone is still looking at this thread, but here goes . . . .


I have a Yanmar 2GM20F-YEU engine installed on my Elan 333 in 2001. Reliable and easy to maintain, but the exhaust elbow weld perished, allowing hot salt water to drip unnoticed onto my fuel pump which got corroded so the manual lever became siezed.


I've just had the pump replaced and discover it leaks oil (1 X 2mm drip every 2.5 minutes = 1 litre every 1,250 hours!) from the manual level pin through the body of the pump.


So I am now asking whether this particular pump is faulty, or I got the wrong part, although it works fine in all other respects. Does anyone know the difference between two different part numbers for what look like identical pumps to me - 129301-52020 and 128270-52010?

You should have a parts warranty claim

[Cruisedog]

Originally Posted by SY Harmony

You should have a parts warranty claim

From China!

[SY Harmony]

Originally Posted by Cruisedog

From China!

Was it an aftermarket part or yanmar original replacement part?

[Cruisedog]

Claimed to be Yanmar original part.

[SY Harmony]

Originally Posted by Cruisedog

Claimed to be Yanmar original part.

Genuine Yanmar parts from a Yanmar dealer carry a parts warranty.

[skipperpete]

I’ve removed and reinstalled quite a few of these little feed pumps, even had a go at drilling out the pivot shaft plug in attempt (failed) to replace the diaphragm. On one pump I got a leak similar to yours but it was my own fault, the access to the pump side of the engine was really difficult and the gasket got out of place while I was struggling to fit the new pump. I could see the leak with a mirror but not the precise source and it was only after removing the pump again that I was able to see the crease in the gasket that was causing the lube oil to leak.

[Dalestr]

Any place fuel can ooze out is a potential air leak when there’s a vacuum in system due to daily thermal cycles when dormant. My Yanmar 2GM20F was oozing a bit at the gasket after 10 years so I removed it, capped off the mounting port and bought a Facet cube pump and plumbed that in. Bought from Pegasus Auto Racing company. Had to choose the lowest pressure version to emulate the Mikuni original pressure, only about 1.5psi.
I wouldn’t recommend this for everyone as it was a bit of work and mechanical pumps are fine — if access is good. The electric does make bleeding quicker.
The pump should be downstream of the primary filter like the original as all pumps need a filter upstream. One other potential advantage is the dry lift rating for these which is typically much greater than the mechanical units. Important if your fuel tank is low in the hull. Beta/Kubota engines have quite weak lift ratings for example.
There may be a different model pump between some 2/3 cylinder GM series engines. The 3GM30 has higher fuel pressure spec than 2GM20…so that might be a stronger diaphragm spring used.

[Ballsnall]

Originally Posted by Cruisedog

So I am now asking whether this particular pump is faulty,

Yes, the pump is faulty, it should not leak oil from the lever shaft. Most likely a pinched oring on assembly.