Checking injectors

[Geek_Guy]

Looking for a quick opinion please.

We had a mechanic take a look at our very old Yanmar. It sounds good, doesn't smoke, starts immediately. The mechanic said even with all that he would recommend removing the injectors and having them checked. His comment was that they could be spraying a small pointed stream rather than a wide more mist.


Since I'm a strong believer in the 'if it ain't broke' philosophy, I have my doubts. But if a small bill would keep it happy in the long term. I'd consider it a cheap preventative measure.

Thoughts appreciated.

[model 10]

I'm with your mechanic on this. The spray pattern gets uneven over time. There could be hot spots, wet spots etc etc. Cylinder wall and piston ring damage is possible.

[a64pilot]

Absolutely have them cleaned and tested. They need to open at the correct pressure too, this is controlled by a spring that is shimmed, over time the spring gets weak and need to be reshimmed.
Think of this as changing oil, and a Diesel is not a good engine to wait until it’s broken to fix it, they live off of PM, preventative maintenance.
You can ignore it for quite a long time actually, then your often faced with a huge bill, as in overhaul or repower sized bill.

[kapnd]

You can perform a quick check of your injectors by loosening the nut that holds the fuel supply tubing to the injector. Back off one cylinder at a time, the engine will slow, and possibly run rougher, then retighten that one and move on to repeat the process on all cylinders.
The key is finding one that does NOT make a change in the engines rhythm.
This does not necessarily mean that it’s a bad injector, there are many things that can cause a dead cylinder, and a bad injector is just one of those, however finding a dead cylinder, I would check the injector as a first, especially considering what was said about the age of the motor.

[hellosailor]

The old fashioned thing was to literally pull the injector, keep the fuel line connected to it, and place the injector in an olive bottle or other tall thin bottle. Then crank the engine and observe the spray pattern and volume.

We took a vote about that once, and decided that twenty year old injectors probably would need to be cleaned and calibrated no matter what. So we ordered new ones, and sent the old ones out for cleaning and calibration. Wasn't THAT expensive (especially when you're not stuck in marine prices) and the spares on the shelf don't really offend anyone. If you don't need the engine for a couple of weeks...Just send the old ones out and wait for them to come back. You're really looking at 48 hours in a shop, plus any shipping time, travel time, backed-up-workload time...all the usual marine delays.

[mcerdos]

Originally Posted by Geek_Guy

Looking for a quick opinion please.

We had a mechanic take a look at our very old Yanmar. It sounds good, doesn't smoke, starts immediately. The mechanic said even with all that he would recommend removing the injectors and having them checked. His comment was that they could be spraying a small pointed stream rather than a wide more mist.


Since I'm a strong believer in the 'if it ain't broke' philosophy, I have my doubts. But if a small bill would keep it happy in the long term. I'd consider it a cheap preventative measure.

Thoughts appreciated.

What does the engine manual state? If I recall correctly checking the injectors is a part of the maintenance schedule.

[Geek_Guy]

Thanks for the thoughts.

Sounds like a solid concensus to have then checked.

So is the removal relatively simple? I have intermediate mechanical skills. Is it just taking an open wrench and unscrewing?

[a64pilot]

Injectors can be held in by a couple of ways, but it’s usually pretty obvious with a big nut holding in the fuel line.
Usually it’s remove that and two nuts holding in the injector with a bar.
However it’s not uncommon for them to be stuck and may take a little exertion to remove. Sometimes spraying liquid wrench around them the day before helps.
Often there is a copper sealing washer that ought to be replaced or at least annealed. Last guy to clean and overhaul mine supplied the washers as part of the deal.
Often loosening the holding bar and then spinning over the engine as if you were going to crank it will have the compression loosen the injector.
Of course have a rag on the fuel lines as a bit of fuel will come out when you turn over the motor.

[Wotname]

Originally Posted by Geek_Guy

Thanks for the thoughts.

Sounds like a solid concensus to have then checked.

So is the removal relatively simple? I have intermediate mechanical skills. Is it just taking an open wrench and unscrewing?

It is relatively simple unless they are stuck!

It sounds like you have a QM series Yanmar; I don't know if you have seen the thread below- one of the issues relate to removing a stuck injector - on an older Yanmar than yours.

http://www.cruisersforum.com/forums/...-202441-2.html

There are other threads on CF about removing injectors, try the custom google search feature (under the search menu).

[theway]

I watched the mechanic do it 7 months ago and it seemed pretty simple (but he knew what he was doing). On the 3GM30, a prerequisite step is removing the fuel return line, be very careful of the copper crush washers... they’re small and could easily fall into a hard to reach spot.

[meridian28]

Those crush washers are one time use

[Bill O]

Originally Posted by a64pilot

Injectors can be held in by a couple of ways, but it’s usually pretty obvious with a big nut holding in the fuel line.
Usually it’s remove that and two nuts holding in the injector with a bar.
However it’s not uncommon for them to be stuck and may take a little exertion to remove. Sometimes spraying liquid wrench around them the day before helps.
Often there is a copper sealing washer that ought to be replaced or at least annealed. Last guy to clean and overhaul mine supplied the washers as part of the deal.
Often loosening the holding bar and then spinning over the engine as if you were going to crank it will have the compression loosen the injector.
Of course have a rag on the fuel lines as a bit of fuel will come out when you turn over the motor.

Agree with this general procedure, but would add a couple of things to make sure crud/particles don't fall in to the cylinder. Prior to removing the injectors, use a compressed air source to blow out crud/particles around the injectors (use safety glasses). Also watch for crud falling off the injectors, hold down bolts, etc. as you start to remove them. Blow out or vacuum out particles as needed.

After removing the injectors put a clean rag (other plug) into the open injector port so nothing falls in while they are out.


Bill O.