Replacing injectors

[Scott T-Bird]

I have a Yanmar 3GM30F with completely unknown engine hours. The hour meter supposedly stopped working long ago so for 20 years I couldn't even estimate the hours. For the past 6 years, engine usage has been light. On my recent trip in the Atlantic, my engine lost RPM very suddenly and quit while bashing through waves on an upwind slog. Limping into Atlantic CIty under sail, I found that at low RPM I could maneuver in the anchorage to set anchor. After a lot of trials in the harbor I found that the middle injector leaks fuel profusely at the base of the injector. I had removed the fuel return pipe to inspect at the top of the injectors and detected no leaking or blockage in the fuel return system. Mixing elbow was clear. Racor and secondary filters where replaced in June so filters were new. However, I changed the Racor as it was dirty (but not necessarily dirty enough to need replacement - but I did it anyway). I found secondary filter (spin on next to the butterfly pump) clean as a whistle.

So I called a mechanic and his almost immediate diagnosis was that the middle injector is irreparably damaged. I'm replacing all 3.

So my question is ... what causes an injector to leak fuel? Could it simply be the hours? Could it be the extremely rough ride I was putting the boat thru? Could it be other engine performance issues? In neutral, the engine feels and sounds normal and powerful. During my trials, the engine ran smoothly and powerfully up to about 2400 rpm and start to fail with higher rpm while running in gear. However, the leaking seemed to worsen as I was making adjustments and trials around the harbor and the leaking persisted even in neutral at all rpm levels. I lived four nights on anchor before finally moving into a marina and getting a mechanic involved. The mechanic explained that the leaking is reduced when the engine is cold and heating up. But when the engine gets heated at running temp and put under load, the heat will allow increased leaking and start to cause the loss in rpm.

 

[BigEasy]

Can you send them to a rebuild service. Years ago I sent the injectors for a Yamaha outboard to a service center for rebuild & recalibration. Good results & very reasonable cost at approximately $30 per injector. Provided a print out with before & after specs.

 

[JamesG161]

So my question is ... what causes an injector to leak fuel?

Normally a bronze washer between the Injector and Engine.
Jim...

 

[Alan Gomes]

Normally a bronze washer between the Injector and Engine.
Jim...

I believe on the Yanmar it's a copper washer. I think this is the part he would need for the GM-series--but definitely do confirm. It may be that there was a change made from earlier (1980s vintage) models.

 

[BigEasy]

Some injectors also have a type of O ring internally; but not all.

 

[jssailem]

Certainly the copper washer may have been ignored when the injector was last removed. Some times these washers stay in the injector hole and a second washer is added in error.

Hard to identify remotely.
I took my injectors to a specialty shop that services injectors for the trucking fleets. They rebuilt them and returned them. They now run like new. If there is a unrepairable issue the shop will tell you. Is it best to get new ones or service the ones you got? In part it depends on the availability and cost of new injectors. Even new out of the box can have defects. In my case the new ones are believed to be made with gold parts by the sellers.

Your experience may be better.

 

[odaydokay]

I also pulled my injectors out many years ago and sent them to a diesel outfit that specialized in cleaning these up. I guess they de-carboned them and put new seals in them or something like that but they have been beautiful ever since. Engine you would not properly idle as it had been overheated apparently, and the injectors had been coked or so I was told by the yard that the sold me the boat.

 

[JamesG161]

washer between the Injector and Engine.

Here mine with clamps too.

50 Hp Volvo Penta engine

Jim...

 

[marcham]

Make sure you get a quote for the labour and parts before you get them rebuilt.... parts costs for Yanmar has gone up.... last injector rebuild I i did cost was 70% of buying new injectors.... I should have just bought new ones and kept the old ones as spares as they were still functional...

 

[jssailem]

Be sure any shop you use has a quality spray pattern test equipment.

Bosch is known as premium piece of equipment. It tests pressures and confirms spray pattern. Both critical to proper performance.

Return of a spray pattern report is an upscale option. Even distribution fine mist spray is the goal.

 

[Davidasailor26]

On my recent trip in the Atlantic, my engine lost RPM very suddenly and quit while bashing through waves on an upwind slog. Limping into Atlantic CIty under sail, I found that at low RPM I could maneuver in the anchorage to set anchor.

This sounds pretty typical of diesel bug getting stirred up and blocking fuel supply. Could there be a screen on your fuel pickup tube or check valve in the fuel line that got partially clogged?If so the injector issue could be just an incidental finding. I’d probably replace the crush washers and check the fuel supply before replacing the injectors. Maybe you’ll need to do the injectors too, but start with the cheaper things to check first.

 

[Scott T-Bird]

If I was in my own slip I might consider more investigation into the actual condition of the injectors. 5 years ago, I had the injectors tested and the spray pattern was perfect. I also replaced the bits that went inside the chamber (under the nozzle nut) before inserting the injectors. They included a new O-ring, cover, protector, rear chamber and chamber gasket (copper washer) so I have a starting point then with solid performance. These parts are all listed in the Parts Catalog of which I have a copy.

I spoke with Mack Boring service tech yesterday about the cause for the leaky injector and the response was that the injector should really be removed & sent out for testing to determine where the leak originates inside the injector. Given that I had already replaced parts relatively recently and because I couldn't stop or modify the leak at all by tightening the flange nuts on the cylinder head, it was more than likely that the injector should be replaced. Sending the injector out for testing could easily be a waste of time - a commodity in short supply.

The engine runs very well until the rpms are increased to the point where leaking affects the fuel delivery. The mechanic says I could limp home (obviously, I can sail once I'm outside the inlet) and deal with it in my home port. But when winds are fickle now and/or switching to NE with steep waves, I'm not enthusiastic about this option. Besides, I have to deal with a difficult inlet at the other end, current in a narrow channel, and then another channel to get to my slip. I don't want to deal with this again with wind potentially on my nose.

Now, with marina fees piling up, a deadline for leaving when slips are no longer available, and my usual opinion that time is far more valuable than money, .... I just want to get the injectors installed to resolve all questions and be on my way. Yes, it's expensive, but I also needed to get home to settle down the home front (that's where I'm at now) and I have tomorrow, Friday and Saturday to get tucked safely back in my own slip.

The other question marks had already been reviewed and resolved (Racor filter replaced, spin-on filter was clean, fuel delivery & return lines all good & mixing elbow is clean. Exhaust system was fine, engine temp all good, air filter ok (I should change it soon, though). I checked into the reputation of the mechanics and they sound good. I suppose I should get some warranty for their work.

One of the complications is that the new injectors have been modified from the original injectors where an adaptor was required to connect each fuel delivery pipe. Because the adaptors are discontinued, I have to install new pipes. I'm replacing all 3 injectors to keep the set consistent (they are 26 years old - so there is that) and delivering the pipes is the hold-up now, otherwise the installation would have been done by now. All will be installed tomorrow. I was skeptical when the mechanic told me this story, but Mack Boring Parts Dept verified so now I'm comfortable with it.

 

[Scott T-Bird]

This sounds pretty typical of diesel bug getting stirred up and blocking fuel supply. Could there be a screen on your fuel pickup tube or check valve in the fuel line that got partially clogged?If so the injector issue could be just an incidental finding. I’d probably replace the crush washers and check the fuel supply before replacing the injectors. Maybe you’ll need to do the injectors too, but start with the cheaper things to check first.

The racor was definitely collecting some gunk and it was dirty when I replaced the filter but I don't think it was contributing to the problem. The engine did have trouble starting after it died but only in the ocean where it was really rough. Once settled down in relatively calm water, starting was never a problem and the engine ran fine at lower rpms. I didn't find the fuel leakage until after I was settled at anchor.

 

[Davidasailor26]

The racor was definitely collecting some gunk and it was dirty when I replaced the filter but I don't think it was contributing to the problem. The engine did have trouble starting after it died but only in the ocean where it was really rough. Once settled down in relatively calm water, starting was never a problem and the engine ran fine at lower rpms. I didn't find the fuel leakage until after I was settled at anchor.

I don’t see any reason why the ocean’s roughness would affect anything about the injectors. The acceleration they’re subjected to from engine vibration is probably lots more than ocean waves. I’m still thinking something larger was clogging the fuel line before the filter, and what you’re seeing in the filter is just smaller debris than what’s getting clogged elsewhere. When you tried to restart in the ocean the debris may have still been churned up, or there may have been some residual disruption to the fuel flow that cleared over time.

 

[Scott T-Bird]

I don’t see any reason why the ocean’s roughness would affect anything about the injectors. The acceleration they’re subjected to from engine vibration is probably lots more than ocean waves. I’m still thinking something larger was clogging the fuel line before the filter, and what you’re seeing in the filter is just smaller debris than what’s getting clogged elsewhere. When you tried to restart in the ocean the debris may have still been churned up, or there may have been some residual disruption to the fuel flow that cleared over time.

I was concerned about fuel pick-up but it's obvious from the way the engine runs now that there isn't anything clogging either the fuel pick-up, the filters or any of the fuel delivery systems, except that the injector is leaking. My purpose for the post was basically to see if anybody had anything to add about why injectors fail eventually, if used long enough. I already decided on Monday what to do about it. When I approached the mechanics about a simple solution (replacing the copper washers, insulator, O-ring etc under the nozzle nut they basically laughed at the idea that those bits would contain the leakage. The mechanic that made the diagnosis said that the commercial guys simply replace injectors at intervals (4,000 hours?) as routine maintenance. I have no idea how many hours are on my boat and I have no illusion that parts that are subjected to so much wear and tear will last forever. So I have no problem putting in new injectors.

I would just like to avoid another episode similar to what I just went thru - given that the engine has been running for 26 years. For instance, how do I know when the injector pump is going to stop working just due to attrition? What other components that aren't being inspected or tested can simply fail without warning. I'm not suggesting that all risk can be eliminated, but I would like to know a bit more about the parts that can be troublesome at the wrong time!