Injector rebuild questions

[woodwright]

I'm rebuilding my injectors and have a few questions. I pulled my injectors apart tonight, and noticed some differences. sitting on top of the nozzle, is a seat with a small button looking thing, and then the spring. On three of my injectors, the seats are different.
http://i447.photobucket.com/albums/qq197/woodwright1/IMG_20120517_201339.jpg
I had 5 of the one on the left, and three of the one on the right.
http://i447.photobucket.com/albums/qq197/woodwright1/IMG_20120517_201422.jpg
Here you can see on the left that the button and seat are held off the body by the spring. The ones on the right are loose and the button will rattle around if you shake them. I have a few extra sets that I've salvaged off of junk motors, and they all appear to be like the tight ones on the left.

Also, my other junk sets have this small washer under the nozzle, but my good set doesn't.
http://i447.photobucket.com/albums/qq197/woodwright1/IMG_20120517_203617.jpg

I'm thinking they're a seal of sorts. Should I put them in my good set? I also bought new nozzles from Rock Auto.

[Robyn]

The little thin metal part is a heat shield.

Possibly different brands/manufs have slight differences in the parts

The injector should not rattle when shook

In rebuilding these, the nozzle needs to be replaced as the tiny little holes where the fuel sprays out wear out from use.

Once the new nozzles are installed, then the seat needs to either turned over so the good side is sealing (or some shops will wet stone these)
New is the best deal though.

Then the spring and shims are installed and the "POP" pressure is set.

Somewhere in the 2000 PSI range will work fine.
The important part is to get all the injectors the same (withing 100 PSI or so)

When testing the injectors, the pressure should build as you pump the tester until you reach the "POP" point. The injectors will POP open and spray.
Continued light pumping right at the POP level should see whats called "Chatter" where the injector sort of pulses while the pressure is right at the break point.

The spray out the nozzle must be a nice fine cone of mist. If your seeing a pee stream or other odd pattern then there are issues that must be corrected.

This is not rocket science. Just take your time, keep the parts clean and you can do a good job.

Without a pop tester though the task is pretty much impossible, as you can't tell what you have.

Having POP pressures all over the map will result in a really rough running engine.
Low pop pressures cause smokey idle, poor performance, poor fuel economy and hard starts.

The same can be said for worn nozzles.
Nozzles that are peeing off in a corner rather than a nice even cone of mist can cause hot spots and eventually engine damage.

Just get all the parts the same, dont mix and match stuff.

after all the years that these injectors have been around and being rebuilt, the likelyhood of all manners of odd stuff is not suprising.

Good luck

Missy

[woodwright]

I finally got my injectors rebuilt and in. I put in new bosch nozzles from RockAuto, lapped all the sealing surfaces with 1500 grit, and cleaned everything very well. They all pressure tested to around 1750, so I put them in last weekend. For the first few days it felt like the power was down, and it smoked more. I replaced the air cleaner and it seemed to help. Do they take some time to break in? Also, it seems like I still have a miss. What else could cause that? And it seems a little harder to start.

[john8662]

You're shooting for 1900 psi.

The springs can be shimmed to increase the pop pressure, I don't know where you'd get the shims though. I have a local shop I deal with that does these on exact pressure to one another, has a lot of shims to choose from, from other builds naturally.

The harder start and smoke is indicative of what you're seeinf with the pop pressure.

Break in, kinda, but not really.

They will change a little when run for a thousand or so miles (usually get quieter).

J

[woodwright]

I've still got this miss to deal with. What could cause that typically? I don't have a diesel compression gauge, so I haven't checked that. Could the IP cause that?

[Robyn]

If it misses at idle, go through and crack loose each injector line until you find the hole thats not firing.

Once you get that done, then you can move on from there.

Does it miss all the time or just at low speed ??

An injector pump can cause a miss.

A cylinder thats low enough to miss at idle speeds will usually be really low.

370-400 PSI compression is good (this is 4 puffs, or four complete cycles though)

Even down in the 300-320 range should still run.

If the miss follows the RPM range then you likely have a bad hole.
Bad rings, leaking valves, possible rocker arm failure, cam lobe failure.

You can do a test without tools this way.

warm the engine up then shut ot off.
Unplug the large pink wire that controls the injector pump.

Now have a helper crank the engine while you listen to it out front.

The cadence of the starter cranking the engine should be even and steady "Ra Ra Ra Ra Ra Ra Ra"
If you get a wild card in there where the cadence of the cranking changes abruptly then goes back to the normal Ra RA RA sound, then you have a bad hole

This is not a substitute for a compression tester, but will get you on the right track.

Once you check this and find the hole thats not firing, then you can proceed.

A bad rocker arm or ?? can keep the valves from opening and will cause a miss.

If the compression is good, and everything seems to be fine in that area, then the IP could be suspect.

How many miles on the rig and has it ever had a fresh IP installed ???


Missy

[woodwright]

I think it only really misses at idle. Seems like it smooths out some. But the power is down and it smokes more. I think its harder to start than it should be. Supposedly, the bottom end and the IP only have about 20K on them. The PO said the head gaskets had failed and he parked it, 10 years ago. When I pulled the heads I didn't notice any obvious problems with the head gaskets, but there were cracks between the valves on 1,7, and 8. I replaced the heads with another set I had that weren't cracked, ut thats all I know about them. I don't know how many miles are on them. The motor they came off of had almost no ridge in the cylinders. I put on new 6.5 head gaskets, and new head bolts after I chased all the threads. I really like the simplicity of these motors and I don't think they deserve the bad wrap they get. But I'm getting rather discouraged. This is my daily driver and I can't afford for it to be down.