Diesel injector testing

[Project_Mayhem]

I'm a new diesel engine owner. I've heard and seen many people with bad injectors and plan on buying spares to keep on hand. I'm debating between buying one or all three. A name brand Denso (original manufacturer for Universal/Kubota) is $60 each or a set of Chinese ones are $60 for all three. If I buy three Denso's I'll replace them and keep my old ones as spares. What's the procedure for diagnosing an individual injector?

 

[jssailem]

Injectors are similar to alternators in that the testing equipment is more expensive than a DIY project should be.

Here is a good summary.

Fuel Injector Cleaning and Flow Testing Service

Best fuel injector service for cleaning dirty, clogged or gummed up injectors. We supply before and after flow testing results. Fast turnaround guaranteed

www.injectorrx.com

I send them out to be serviced. Most diesel mechanics do the same.

 

[Project_Mayhem]

Is flow testing the only way to test for proper function? Is there a reasonable way to figure out which injector is bad besides a flow and spray pattern test?

 

[jssailem]

Diesel engines are simple machines. They utilize atomized fuel, air, and compression to produce a combustion that drives the pistons. The timing and the spray (atomization of fuel injected) are critical elements of the process.
No. There is not a precise method. The diesel mechanics I have chatted with have injectors tested when they suspect the fuel mixture from the injector is an issue. Even brand-new in-a-box injectors can produce a bad spray pattern that affects fuel efficiency/performance.

 

[Davidasailor26]

Do you know how many hours the current injectors have and if your engine has any problems indicative of injector issues? Although they do have problems sometimes I don’t think I’d bother having a spare set unless I really thought they were on their way out or I were planning an extended trip somewhere remote.

 

[Project_Mayhem]

The engine is 30 years old but only has 934 hours on it. I've heard enough complaints regarding injectors that I want to keep one on hand.

 

[Michael Davis]

I have two Perkins 4-108’s. I knew one had bad injectors so I watched a couple of UTUBE videos, bought a pressure testing tool for $100 cdn ( about $70 US) and tested and adjusted all eight injectors. You will have to buy new crush washers if you replace or repair injectors.

 

[Michael Davis]

The engine is 30 years old but only has 934 hours on it. I've heard enough complaints regarding injectors that I want to keep one on hand.

My Perkins is a 1984 with almost 7000 hours. Still going strong.

 

[Tally Ho]

Unless you are planning on taking your boat around the world, I don’t think I would worry about having spares on board…the engine will run on 2 cylinders enough to get you into a marina.

That engine seems pretty “young” in the diesel world. My Yanmar 2GM20F has about 2,100 hours on it. Runs strong.

If anything, pull the injectors over the winter and have them serviced.

Greg

 

[Project_Mayhem]

the engine will run on 2 cylinders enough to get you into a marina.

Excellent point Greg! I'll pick up one Chinese injector just in case

 

[Tally Ho]

Excellent point Greg! I'll pick up one Chinese injector just in case

That will give you some peace of mind

Greg

 

[Hayden Watson]

I will be replacing the injectors in my M25XP in the spring. I had an oil analysis done and it showed everything was fine except for raw diesel in the oil. This is typically caused by one of two things. Long idling or leaking injectors. I never let the engine idle longer than it takes to pull the eye loops off the deck cleats so that is not the problem...
My plan is to get the aftermarket injectors at $60 for the set so I will let you know sometime next year as to how that works out. I will keep the old ones just in case they pack it in.

 

[Blitz]

I was told be a well admired Yanmar mechanic that you shouldn't worry unless you are having issues, even with 2000 plus hours. He suggested if suspect to check each by running engine and cracking open the connections one at a time. If the engine RPMs don't change my much when you disconnect one versus the othera then you can narrow it down.
He also said that it was so costly to send them out and test and clean them them properly that he would just replace them as opposed to testing and cleaning.

But this may be due to Yanmar parts being so expensive.

 

[Project_Mayhem]

While we're on the subject, what causes these small injectors to, well, inject? They aren't electrical. Is there typically a cam shaft to apply pressure to the correct injector at the right time?

I will be replacing the injectors in my M25XP in the spring. I had an oil analysis done and it showed everything was fine except for raw diesel in the oil. This is typically caused by one of two things. Long idling or leaking injectors. I never let the engine idle longer than it takes to pull the eye loops off the deck cleats so that is not the problem...
My plan is to get the aftermarket injectors at $60 for the set so I will let you know sometime next year as to how that works out. I will keep the old ones just in case they pack it in.

Interesting. I would've thought that diesel in the oil would be a sign of leaking piston rings but I can see how trace amounts could get into the oil under the situations you describe

I was told be a well admired Yanmar mechanic that you shouldn't worry unless you are having issues, even with 2000 plus hours. He suggested if suspect to check each by running engine and cracking open the connections one at a time. If the engine RPMs don't change my much when you disconnect one versus the othera then you can narrow it down.
He also said that it was so costly to send them out and test and clean them them properly that he would just replace them as opposed to testing and cleaning.

But this may be due to Yanmar parts being so expensive.

Got it. I was under the impression that the injectors were connected by a rail or hard line like on a car

 

[jssailem]

what causes these small injectors to, well, inject?

Reminds me of auto shop… A video oh great.

 

[Tally Ho]

That was a good video, but this one is really cool (for those pyromaniacs out there).

Greg

 

[jssailem]

Difference between educational and just plain fun!

 

[Tally Ho]

I saw a video where a guy was rebuilding his old Yanmar 2GM20 on his boat (he was a world cruiser). To test his injectors, he removed it from the engine, reconnected it to the high-pressure hose, pointed it at a piece of cardboard about 12 inches away from the top, and turned the engine over. Can’t remember if he hand cranked it or hit the starter button for a second. Then looked at the spray pattern left on the cardboard.

I don’t re ember if he tried to clean them or replaced them or what. But I think he did get the engine running again.

Greg

 

[Ralph Johnstone]

That was a good video, but this one is really cool (for those pyromaniacs out there).

Incredible. How do you pull these gems out of the internet ?

But you're wasting my whole day away. Survival up her in the frozen (well sodden, anyway) North is a good deal more challenging that sitting on a lounge chair and sipping pina coladas in SW Florida. I'm off to see if I can find anything to eat in the traps I've set.

 

[jssailem]

It is true, one can spray diesel fuel at a cardboard target and get an image. One can pull an injector and removing the injector while still attached to the high pressure system, squirt diesel fuel to confirm that fuel is moving through the system, filling the air within the engine compartment with cologne of diesel in the morning.

There is a significant difference from confirming a spray and a test of measured fuel atomization based on the engine specifications.

While cruising, trying to get to the nearest harbor on an engine which is acting up, it is very different set of circumstances than preparing an engine while in port for a long passage or a season of sailing.

We try (or should try) to operate our boats with optimization of fuel systems, minimization of fuel waste and recognition of exhaust contamination when excess fuel is discharged. If these criteria are to be achieved then professional testing of the injector spray volume and pattern is a reasonable expense to incur. In my opinion.