Yanma 3QM30 Injection Pump User removable?

[svnakia]

Hi,
I have a yanmar 3QM30 which has developed a fuel leak around one of the injection pump cylinders (for a lack of a better word). From the diagram in the manual it looks like an 'O' ring has gone.

The manual is pretty clear that dismantling the pump is out of the question for a 'regular guy'. How about removing and re-installing the pump?

I'm basically mechanical, I do all the work on my boat. But the injection pump is one piece of black magic I haven't gotten into.

The boat (and me) is in Manzanillo Mexico and while there are a great number of diesel labs here (this is a major shipping port) there aren't that many mechanics available to work on the problem.

Any advice for removing and re-installing the pump would be greatly appreciated. Is this something you can do if you watch what you're doing or should it be left to an experienced mechanic?

John
SV NAKIA
Web Log of Sailing Vessel NAKIA

[SkiprJohn]

Aloha John,

You can remove and reinstall the injection pump on your own. I hope you have a shop manual but if you don't then don't worry too much about it. The key is that you do not want to change the rotation of the pump or the engine in the least little bit once you have it removed. You will want your injection pump servicer to return it in the exact same rotation so that you don't have to worry too much about timing it. (You'll always worry) You can make little marks here and there to make certain things stay in time.

I've done this as a novice on a Mercedes diesel and have to restate very clearly that you don't want to turn the pump or rotate the your engine at all until you've marked it properly for timing purposes. In the case of your engine. Don't rotate it until you have reinstalled the pump.

Good luck.

Regards, --JohnL--

[Chief Engineer]

Don't rotate the engine at all. The plungers in the Injection pump will all extend, and make sure if there are any shims (they look like gaskets but aren't) stay on the boat.

When you get ready to re-install come back to the board

[svnakia]

Hi guys,
Thanks for the support. If understand the shop manual correctly, the injection pump is timed by shims between the pump and the block not by rotating the pump. The pump is rectangular and has a 4 bolt paturn so it's not very likely that it will rotate in it's mount. But I will take your advice to heart and not turn anything, pump, engine or prop until the injection pump is back in place and ready to run.

John

[svnakia]

OK, it looks like it's definately an O-Ring seal problem. If you look at the diagram below you can see the fuel passage that the high pressure plunger draws it's fuel from. This passage is supplied by the feed pump and has pretty low pressure in it.

Today I found that I can cause the leak to occur just by pumping the priming lever on the feed pump, without the engine running! In the bottom photo you can see fuel pooling under delivery valve spring holder.

The thing I'm trying to figure out now is if I can replace these O-Rings without removing the pump. The pump is mounted horizontally, which may make getting the delivery valve seat/valve/spring/seal in place chalenging... More to come.

[SkiprJohn]

Aloha John,
You might be able to but I got into $850 worth of trouble when I messed around with a Bosch FI pump on a 4 cyl Mercedes. So, I wouldn't do it.
JohnL

[never monday]

Yes it could be done in the boat.
BUT, this pump is 20+ years old. Take it out, and have a Bosch Diesel Injection shop go thru it. It'll be beter in the long run.

[svnakia]

Good point, never_monday. I guess the thing that worries me most, after reading the service manual over and over for the last several days, is that there are a million and one ways to screw up re-building a pump like this. For instance, the volume of fuel delivered by each high pressure pump (since there are three cylinders, there are three individual high pressure pumps) has to be within 3% of each other. If not, "the engine output will drop and/or one cylinder will overheat".

Do I really want to trust this to a lab here in mexico? Will they have all the equipment required to test and tune the pump propperly? Or do I go with the simple fix that doesn't require running the risk of de-timing the pump.

[never monday]

There is no issue with timing that pump except the thin brass shims is sets on. pull the pump and take it to a Bosch authorized service center. or ship it to someone in the states who can handle it.

[svnakia]

Looks like this might be a more common problem. Here's a link to a guy showing how to replace these O-Rings on a Mercedes car.

Mercedes Injection Pump O Ring R

I got the injection pump out, though the shims are not in very good shape. The shims had sealant on them which made them come out unevenly and as a result they are pretty bent up. Luckily it looks like a number of Yanmar tractor motors use these same shims so I should be able to get a replacement set. We'll see.

FWIW, according to the service manual it is possible to change the timing on each individual cylinder by adding/removing shims inside the fuel injection pump. You adance the timing by adding shims under each plunger and retard the timing by adding shims under the entire pump.

John

[never monday]

IF the shims under the pump are not torn, they are reusable. Don't worry about the sealant.
Now that the pump is out. Have a shop do it.

[svnakia]

I thought I'd update on this and let everyone know what the results were.

The shop that did the service on the pump said 'there are some worn parts and we need to replace them'. Two weeks later they were still unable to get parts so I took the situation in hand and ordered new plunger/barrels and delivery valves as well as a full set of seals. Almost $500 USD in parts.

It took a week or so for the parts to be delivered by a friend who brought them down from the states to Puerto Vallarta. It was a miracle, actually, because all these parts are packed in fuel. Imagine trying to carry on a plane three plastic cylinders, about the size of a shot gun shell, with a piece of metal in it and a 1/2" of diesel fuel in the bottom.

The injection shop got the pump back to me in a couple days after receiving the parts and charged me $200 in labor. I installed the pump in an afternoon (it only took me two tries to get the timing right).

So, after paying for a marina for three weeks and $700 USD for parts and labor I have a re-built fuel injection pump that runs about the same as it did before. At least it doesn't leak fuel, which was the original problem. A _new_ injection pump is about $1000.