A modern mystery (Yanmar injectors)

[FulmenParticipant @fulmen]

So I’m like servicing the injectors on my boat, one of those ubiquitous (I actually spelled that right on the first go) 3 cylinder Yanmars. The nozzles look fine, so not much to do except removing some rust, dirt and carbon build up. But after 40 years I’m sure the pressure needs adjustment. My local mechanic can test them, but he doesn’t have a lot of shims so I figured I would buy some just in case. But nobody sells them.

Now the nozzles I can get everywhere, best deal I could find was 6 for 30EUR. So why are the shims unobtainium?

[David JuppParticipant @davidjupp51506]

These ?

https://www.dam-marine.com/gb/injector/527-set-of-yanmar-injector-shims-110250-53150.html

[FulmenParticipant @fulmen]

Idunno, they don’t list what engine it’s for.

[Clive Brown 1Participant @clivebrown1]

French Marine of Colchester deal with Yanmars ancient and modern. You don’t say what engine you have, but, for example, they list “plate assembly adjust” for the GM series injectors. Is this the type of thing you need. Might save money of course if you test the injector pressur before splashing out.

[FulmenParticipant @fulmen]

I might have overstated how hard they are to find somewhat  🙂

Using the yanmar parts number I’ve found several vendors, but there is still a weird mismatch here. The nozzles are sold by the crate like eggs, in fact I can buy them for the same price as a set of shims. It’s as if everybody swap these nozzles out at the drop of a hat without ever checking the pressure.

As far as I can tell mine are fine after 40 years of light duty, but the spring is appr 0,5mm shorter than factory specs.  According to the manual we’re talking appr 10 bars per 0,1mm, this could explain the drop in power at full throttle (3-400 rpm).

[Howard LewisParticipant @howardlewis46836]

Since you are looking for shims, presumably your local mechanic has found the breaking pressures to be out of spec?

If within spec, and spraying satisfactorily, my advice is to leave well alone. (And that includes not trying nto decarbonise the spray holes in the nozzles; you are talking just a few thou here, probably less than 0.020″ if the engine is direct binjection.

If the spray quality is poor, that will reduce power, and mean that the nozzles and needles need either attention (Lapping or replacement)

If the breaking pressure is lower than spec, I would expect fuel delivery to have increased (Although you will have no means of checking this, withouit a test machine)

The loss of power MIGHT be due to other things, such the fact that a lower breaking presure will effectively over advance the injection timing, or if the spray quality has reduced, that might decrease power, at the expense of slightly increased smoke levels.

If the injection pump is feeling the effects of old age (Plunger/barrel or delivery valve wear) that might well reduce fuel delivery and power. Have you had the pump checked ?

Also, valve sealing may be worse. A compression test might show this.(Assumes that the air filter, or exhaust system, is not restrictive)

Howard

[FulmenParticipant @fulmen]

No, I just assume they will need adjustment after 40 years. Might as well have the shims ready, they’re not that expensive.

Haven’t checked the pump or compression, that’s a bit too much work for now. If the injectors are fine I’ll just have to live with what I’ve got.

[Howard LewisParticipant @howardlewis46836]

Very wise!

Just check the injectors, if the breaking pressure is within spec, and they spray ok, just brefit.

“If it ain’t broke, don’t fix it”

Sleckeming an injector retaining nut could shearb the stud and that makes anotherv problem, that ndidn’t exist before.  Sod’s law says that the stud will shear off level (IF you are lucky) or below flush and then that has to be removed.

Howard

[Fulmen]

On Fulmen Said:

this could explain the drop in power at full throttle (3-400 rpm).

My first suspicion would be some restriction in the fuel supply – a clogged filter or something. If you’ve picked up the dreaded “diesel bug” it can clog the tank pickup pipe as well as any filter(s) in the line.

Second suspicion would be a clogged exhaust elbow.

(Ex 2GM owner).

[FulmenParticipant @fulmen]

I discovered the diesel bug last year, so the fuel system has been thoroughly cleaned including a fresh filter. That’s also part of the reason for this service, I did find some crud in the nozzles (the filter body had a rust hole).

Never thought about the exhaust though. It’s a fairly large pipe so a clog seems unlikely, but it’s simple enough to check…

 

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