Ok guy's, going to rely on you from now on. I have one injector with a hair crack half way around it. Was going to replace all might mighty expensive.
That neighbor has some out of a 6.9 and says there all the same, interchangeable. Is this so?? Mine's a 7.3. Also is there any way to tell if there any good before installing? With this engine, not sure how many miles but the short time I drove it before starting to replace parts didn't burn any oil. So far I've put in solid steel flywheel, clutch & Pressure plate, throw out bearing, new slave cyl, Slave cyl master cyl, new brake master cyl , new power boost, remanufactured steering box, new water pump, new glow plugs, new controller for glow plugs, new "O"ring seal kit + hoses etc. If I can use the injectors from the 6.9 it would save me about $350. thank you in advance Bill oh also forgot 6 new tires. will add picture when I get it painted .

 

You will be fine with 6.9 injectors. Pop tester only way to check them out.

 

What's a pop tester and where do I get one?

 

Frankly, its not worth buying / building one for a one off deal, an equipment shop or diesel shop that has a reputation for working on older stuff might have one. That said, i wouldnt really trust em unless theyre known for working on idi's. Secondly, what they would charge for it would probably pay for half a set of injectors. Fast and dirty way to assume theyre good is if theyre not wet, but if you look very closely at the pintle / nozzle, they will have a ring around the pintle where the seat is hammered, that means theyre "shot". For the most part, theyre all the same, theyre really not, but the differences are quite minor. Frankly, if you just have the one bad one, id hit a pull a part and just snag an injector that doesnt show signs of leaking or broke / breaking (the ring on the bottom). IDI injectors are simple, for the most part they dont have any issues, they will normally go forever, but that doesnt mean they should, realistically, they should be replaced every 150k or so, but ive seen IDI's run "fine" with over half a million miles on the stock pump and injectors, (fine, albeit not well).

If you have an injector bore that is really sooted up, i think its a 3/4" pipe fitting brush that fits well, or you can use a battery terminal cleaner, follow with compressed air. You will need to get the soot out, or will be a bearcat to get a new stick sealed.

 

You can take your injectors to a diesel shop and they can pop test them for a fee. I tried this when I replaced the injectors on my 6.9. Unfortunately, the shop just wanted me to buy new injectors and they never tested them. I have a feeling they just said they were "bad."

For a pop tester at home there's plenty of jubk on the market. Make sure you do your research before buying one. There are also threads out there on building your own with a bottle jack.

 

Or a grease gun.

 

The actual injection pop testers from back in the day (I have a really old one) were just a steel on steel bore/piston. No orings no seals just good quality machine work.

You can buy Chinese ones on fleabay and such for 125-175$

But again they don't really pay for themselves unless you use them more than one go around

 

Most are basically like this. Besides popoff pressure, spray pattern has to be correct. The one our shop had would test Cummins, Detroit, and other brand injectors.

 

before i put the used 6.9 injectors in, i would ask how many miles are on them and why he removed them. if the answer to miles is over 100k miles, i would not bother using them for anything but cores.

 

Spray pattern is basically unimportant in an IDI(*) - what you care about, though, is any leakdown and the popoff pressure. You also want to make sure that it pops off "crisply" and not kind of "mushy". You won't understand this until you test a couple of injectors, then you'll know exactly what I mean.

(*) The reason for this is that fuel gets sprayed against a hot pre-cup, where it vaporizes instantly. "pintle-less" injectors(where the spray pattern is basically just a stream) is what you get with R&D's Stage 1 injectors, and they work just fine.
Might produce slightly more smoke when starting cold, but that's mainly controlled via timing and glow plugs anyway.

 

So if the popoff pressure is OK but the pattern comes out like a squirt gun stream the engine will run A-OK? Been there, done that with a set of new injectors with really bad spray patterns and the engine idled and ran so bad I had to send them back. I also find it odd the IP and injection shop manuals call for and illustrate a specific spray pattern.
Yep, I think I barely understand, I've tested dozens of injectors over many years on our Bacharach tester, all types and most all brands.
And Stanadyne specs DO allow for a certain number of leakdrown drips per minute at a certain constant pressure while on the tester.

 

As long as its a fine mist. Spray pattern is not critical as long as their is no droplets.

 

Gee, thank you for clearing that up.

 

Well, considering I'm running R&D Stage-1 injectors in my main rig, which have the bottom seat drilled out and the spray pattern on these is straight down(because there's no angle at the bottom to spread it out) and they have been working just fine for the last 20+K miles...

Were your injectors pop-pressure matched? The ones with the bad spray pattern? Because that's usually the issue with rough idle, not the pattern.


I generally see they either seal well, in which case the pressure will slowly drop to a certain point(usually around 1K PSI) and won't continue leaking beyond that, or they leak. In which case the pressure will just plain continue dropping.
The first case are good. The second case, not so much.

 

Yes, the popoff pressures were within specs. After installing them it idled so rough that the shift lever rattled back and forth (5 spd.). I don't own my own "at home" tester and didn't have access to the shop's, so after a couple days I yanked them out, took them in to a Cummins dealership. The owner's a friend of mine and I watched him test them and the patterns were all over the map. Took in the exchanged set and they checked out fine.