Replacement Of Fuel Injectors For Yanmar 3GM30

[SmoothSailing5]

Have a 1989 Yanmar 3GM30 with 1100 hours. End of last season had problem with white smoke exhaust and hard starting. Thanks to ideas from forum, removed the fuel injectors and found #3 needed to be replaced. Now have a question about reassembling. Quite sure that the injectors had been removed earlier by a previous owner as there were no rubber O rings between injectors and block and no chamber gasket/washer in cylinders. I will replace O ring gaskets but not sure how many chamber gaskets/washers to use. The Yanmar Parts Fig. 15 for Cylinder Head shows 2 chamber gaskets/washers in each cylinder but I was thinking of using only one. Has anyone come across this problem? Thanks in advance for your help!

[perchance]

If the manual says two, then two it is. They paid an engineer a lot of money to figure out one won't work.

[terrylad]

My 3GM30 runs fine at 1850rpm in forward or reverse. Over 2000 rpm the engine emits a loud "clacking" sound and starts to misfire. The exhaust chuffs out blue/white smoke. Increasing the revs produces blackish smoke and the engine loses rpm, sometimes shutting down. Easing the throttle back allows the engine to recover and run on all three cylinders again (under 2K rpm).

I have changed filters and bled the system. To check that the fuel was good I ran the engine with the intake and return fuel lines running into a bucket of fresh diesel. I also ran a can of "Diesel Purge" through the engine while running under load. This did not change the symptoms of higher rev failure. Obviously, I suspect that I have one or more sticky injectors, but I don't know for sure.

I tried to isolate the injector by using the decompression lever one at a time with the engine under load. I could not detect the symptom of failure at any rpm, which seemed to limit at about 2250 on two cylinders.

I'm reluctant to pull the injectors, assuming that they will be well and truly stuck. I've heard that you can release the injector flange nuts a few turns and then crank the engine, allowing the compression to budge the injector up a fraction of an inch, breaking the initial seal. Is this a reasonable way to coax them out?

Have you seen these symptoms before? Can I do the necessary work to effect a repair myself with basic boat tools?

I'd greatly appreciate your response.

[glynhome]

Hi, I had pretty much the same issue last week. All of a sudden at cruising revs (2800) the engine let out clouds of white smoke and rattled. Strangely it held 1800 revs fine for a couple of hours but then it happened again close to port so I limped in on 1200 revs.

I had an engineer look at the injectors, they came out easily and were not in good shape. These have been repaired and replaced but on running up the engine the problem came back even under no load.

I am now having the fuel pump checked out and also the mixing elbow replaced and will see what happens.

The compression is good and there's plenty of raw water flow.

How did you get on with solving the problem?

Glyn

[terrylad]

I pulled the injectors (quite easily as it turns out) and had them pop tested at a local diesel garage. They all tested OK. Put it all back and ran fine for 1/2 hour under load, then back it came.

The symptoms are still there and are getting worse.

I've run the engine with clean fuel direct from a bucket to the lift pump. I've gone over the whole fuel system (from tank vent to tank bottom to clearing lines and changing filters). Some weeks ago I removed the exhaust elbow and cleaned it out with muriatic acid (it was partially blocked).

No change. The symptoms now appear after 10 minutes of warmup. The engine runs fine at 3K rpm and then starts choking itself, rattling like mad with plumes of blue/white smoke out the exhaust. Quickly shutting back the throttle allows recovery, and the exhaust spits out black fluid (unburnt fuel?) for a second or two and then the engine runs smoothly until I take it over 2K rpm.

So I'm finally waiting for a Yanmar mechanic to become available to diagnose whether its the injector pump or bad injectors after all. Perhaps the pop test wasn't enough to develop the problem, who knows? The local guy is up to his ears in projects and I'm stuck for a few weeks until he's available.

[GordMay]

Greetings and welcome aboard the CF, Glyn.

[glynhome]

Terrylad, thanks for the update, the engineers are all over my engine this week so I'll keep you posted.

Thanks for the welcome Gordmay.

[terrylad]

Good luck, Glynhome, I hope its something simple. Please let me know the result. It may become a case of "hit and miss" between the injectors, injector pump and lift pump.
Not to confuse the issue too much, but I was running on straight biodiesel last year, and topped up with regular diesel this year. The fuel in the lines was pretty mucky as the new mixture progressed through the racor. Its since all been cleaned out.
Are you in Portsmouth NH or RI?

[glynhome]

Cheers, so do I.

I'm in Portsmouth UK!

[olepedersen]

I am having trouble getting #3 injector out 2weeks of pb blaster, and heavy tapping and pulling will not budge it. #1&2 came out ok . Open to any suggestions,the head is off Help Please .Ole

[Dsanduril]

See if your local diesel mechanic will loan you his slide hammer?

I can't count the number of hours I've spend trying to get stuck injectors out using the tools I own, the right tool took about 30 seconds.

The slide hammer has an adapter (or set of adapters) that screw onto the top of the injector. A couple of strokes are usually all it takes to get the thing budging.

The shop where I take the injectors for testing/rebuilding is more than happy to loan their's out for a couple of hours.

[terrylad]

My original misfiring symptom only comes in after the engine warms up for 10 minutes or more, so I thought it might be heat related. I tested the thermostat in boiling water and it worked fine. Didn't check the operating temperatures though and I didn't take out the water pump to check it. I acid washed the heat exchanger and put it all back with new O rings and gaskets and green 50/50 with no problems.

Running the engine produced the same damned symptom. Now I've noticed that after the symptom of misfiring persists, if the engine dies it won't restart. The starter motor bogs down. Turning it over with the decompression levers engaged seems to allow it to spin normally (i.e., the engine is hopefully not overheated). It feels like compression is too great for some reason. It spins normally when cooled down.

Still no response from the local Yanmar mechanics....

[perchance]

In your post you mention the starter lugging until you open the decompression levers.
It sounds like the engine is on the verge of hydro locking due to the accumulation of excess fuel caused by the misfiring.
Something you might want to look into to avoid bending a rod if this is in fact the case.

[NCboatrx]

Terrylad, I suspect that your injection pump needs attention. The starter motor working hard is the clue as your injection pump has a device that advances the timing and I suspect that this is stuck. This will also account for all the running issues that you are having.

[terrylad]

Originally Posted by NCboatrx

Terrylad, I suspect that your injection pump needs attention. The starter motor working hard is the clue as your injection pump has a device that advances the timing and I suspect that this is stuck. This will also account for all the running issues that you are having.

Looks like we're on to something at last. I'll pull the injection pump and take a look.

I guess that losing timing by pulling the pump would be an issue, having never done it before, so I plan to go by the book taking it out and photographing the position of the slider to reproduce when I put it back.

Any advice on fiddling with this piece of contankerous equipment? I feel like I'm doing heart surgery.....