Injector Armature Clearance-What do I need surface Ground? - Diesel Forum

777funk · 03-09-2010, 10:58 AM

I just took one of my injectors apart to take a look inside. I have been having hard cold starts due to the armature clearance being too little (measured close to zero). It starts fine if I plug it in and the glow plugs are brand new as is the relay. They are getting power.

So... the next step, measure the injector armature clearance and see what it is... I did this and as noted above it's very close to zero if not right at zero.

My first thought was order an injector kit and rebuild but after talking to the two companies selling injector rebuild kits, they both said why not just order new/rebuilt injectors since mine have miles on them.

But on second thought, I can't really swing that right now. My wife and I have our 4th on the way (due any day now) and things are tight. And... I'd like to learn. I like to do as much of my own work as I can to save money and because I don't like the run around that many mechanics have given me over the years.

All that to bring me to this point, I tore an injector (1 of 8) apart last night and here's what I saw. The plunger looked very smooth and measured the same all the way up and down (in thousandths using a micrometer and caliper both confirmed... I really need a set of gauge pins and sleeves but hey... I'm not a machinist!).

So I think they're worth re-using. The external o-rings are worn. The inners look ok but I don't think people re-use the inner o-rings.

So my question... I want to get my armature clearance back. I don't want to shim, I'd rather grind. I'm assuming the Adapter (just below the armature) is what needs to be ground. I have a plan but I don't want to do anything until I know what I'm doing. But here's the plan:

DeWalt Radial Arm Saw with a fine tuned table (Mr. Sawdust table) with a medium (60 Grit) grinding wheel on the arbor. This is my poor man's surface grinder and I should be able to get (with a fixture to hold the Injector's Adapter plate flat and still) the plate within 1-2 thousandths. I'm betting I can get it within 1 thousandth with a little care and patience
Take off the required amount to have 4 thousandths between the Armature and the Adapter plate.

Am I off here or missing/overlooking anything?

I highlighted in red the adapter. I plan on removing material from the bottom side (opposite of where the armature contacts) of this plate.

Just for extras... here's the plunger. You can obviously see where the stroke is at (the coating is worn off). This is from a set of AO injectors that looks like it was rebuilt in 1999. But overall the plunger in this one at least looks pretty good. The diameter measurement was consistent from the non wear area to the wear area.

Stan96 · 03-09-2010, 09:46 PM

Just a wild guess here because I don't know anything about injectors, but if you shim something, you can always remove the shim, but you can't ungrind something, would it be expensive to replace the ground part if you have too?

Nit · 03-10-2010, 01:22 AM

after many , many sets of injectors, beleive me I have been doing this for years, I had teh very first set in Canada, after 6 or so sets I drove down to SLC where they were made and proved that teh injector clearance was a real issue adn we determined how to fix it. You need to take off about .003", completely flat.

I am not saying this to be mean, but are you stupid?, a saw and 60grit?

pay teh money and buy new ones, you will SAVE money by not screwing it up yourself. I have had 2 friends who can biult anything that are real machinists tell me they don't even have teh equipment or time , and I don't have enough money for them to jig it up for a one off set.

shim them if you want to save money , but don't try this.

777funk · 03-10-2010, 09:18 AM

Quote:

Originally Posted by Nit

after many , many sets of injectors, beleive me I have been doing this for years, I had teh very first set in Canada, after 6 or so sets I drove down to SLC where they were made and proved that teh injector clearance was a real issue adn we determined how to fix it. You need to take off about .003", completely flat.

I am not saying this to be mean, but are you stupid?, a saw and 60grit?

pay teh money and buy new ones, you will SAVE money by not screwing it up yourself. I have had 2 friends who can biult anything that are real machinists tell me they don't even have teh equipment or time , and I don't have enough money for them to jig it up for a one off set.

shim them if you want to save money , but don't try this.

I'd bet I can get flat within 0.001" with the right setup and taking a little off at a time (half a thousandth or so). And yes... saw, grinding wheel.

I agree with the first poster... You can't get what's ground off back; you can add or remove a shim. That makes more sense to me than grinding.

But no... I'm not stupid by what I mentioned. If you have seen a fine tuned old cast iron DeWalt radial arm saw you'd know what I mean. On a small item like this, it would be VERY possible to get within 0.001" all the way across the surface with a little care. It's all in how accurate your machine is and in how rigid and square the table is. Google Mr. Sawdust table and you'll see what I mean.

Now is the saw the first choice for the job? Heck no. I'm just saying it could be done.

Most shops I've talked to actually do grind the injector to get clearance. I don't know which machine shop wouldn't have a surface grinder. That's a very common machine tool.

artificer · 03-10-2010, 09:45 AM

I'd add to the "shim it" crowd. If you are thinking of replacing the adapter, but want to try and grind first, I have an alternative method.

Find a VERY flat surface. I use the cast iron table on our vertical metal cutting bandsaw. Tape some 120grit sandpaper to the surface. Very carefully, making sure to apply even presure, rub the adapter on the sandpaper in a figure 8 pattern. Before you start, measure the thickness around the edge. After you remove some material, remeasure to ensure that you are uniform, and not rocking the part. You can move up to whatever grit you want, for whatever finish you want. 2500 grit gives a mirror finish, but gross overkill for this operation.

This is a last resort/cheap emergency method, but you can get good results if you're careful. Shims are just too inexpensive to make, in comparison to messing up the adapter.

Michael

Nit · 03-11-2010, 09:59 AM

I do understand the tools you mean and the skill level it takes to operate them, however within .001" is a bare min for this job, you only have about .002-.003" to play with , or teh magnet will sit tilted. I like the sandpaper method better, as you only really need about 1.5-2 thou off it.

Its obvious that you are capable adn willing to tear down to this level and smart enough to ask before doing. Let us know how it turns out.

Craig

777funk · 03-11-2010, 02:38 PM

Quote:

Originally Posted by Nit

I do understand the tools you mean and the skill level it takes to operate them, however within .001" is a bare min for this job, you only have about .002-.003" to play with , or teh magnet will sit tilted. I like the sandpaper method better, as you only really need about 1.5-2 thou off it.

Its obvious that you are capable adn willing to tear down to this level and smart enough to ask before doing. Let us know how it turns out.

Craig

Will do Craig. I understand the warning. Definitely something to not be taken lightly. I realize in something where thousandths count. So the point is 100% taken and appreciated. I am going the shim route.

The injectors are running perfectly just not starting well in the morning. After seeing the inside moving parts of the first one, I feel halfway decent with the way they look. We'll see how it goes. I'd love to get them rebuilt from the ground up or get a nice new set of Alliants but with lots of bills and a 4th child on the way any day now, DIY is the best way at the moment (driving a Powerstroke gets expensive and if I'm not careful I might not be able to afford it!). I don't want to go back to gas if I can avoid it. So this is the fix for me. At least for now.

And it'll be a fun little bit of an adventure. I've rebuild mechanical injectors on my cars in the past (Injection pump cars). I figured that even with more internal parts in these HEUIs I should be able to do it. We'll see how it goes.

Nit · 03-12-2010, 11:33 AM

the best way I found years ago, was to get a sheet of .0025-.003 shim stock in brass, normally used to shim engine bearings, and a set of hole punches, . Punch teh little one first , then the large one around it, they are very small washers you are making.

777funk · 03-12-2010, 12:12 PM

Quote:

Originally Posted by Nit

the best way I found years ago, was to get a sheet of .0025-.003 shim stock in brass, normally used to shim engine bearings, and a set of hole punches, . Punch teh little one first , then the large one around it, they are very small washers you are making.

Would tin foil work? I think tin foil meets those dimensions. I've also got some copper foil that may meet the spec.

777funk · 03-13-2010, 10:33 PM

At this point I think I'm back to grinding (vs shimming).

I'm getting:
Oil Adapter/Armature ---> less than 0.002"
Armature/Solenoid ---> 0.013"
Energized Armature/Solenoid ---> less than 0.002"

One tip for anyone taking Energized Armature/Solenoid measurements... use a NON metallic measuring device (i.e. microfiche, piece of paper, etc) Metallic feeler gauges are not an accurate way to do the job because the solenoid/electromagnet grabs the metal and makes it really hard to get a measurement. I didn't realize this until I actually looked and saw light passing through between the armature and solenoid.

Anyways, I don't think I will be trying to shim anything at this point. If I do it will move the Armature even closer to the Solenoid which is obviously not what I want to do at this point. I will be grinding. I'm not sure the best place to grind. I think it'll be easier to grind the top of the Adapter (flat and easy to fixture) but it seems like most grind the injector body. There is around 0.010" between the adapter's top and the sleeve's top. So I guess I should have enough to easily grind a few thousandths off before hitting the top of the sleeve (would limit armature clearance).

After finishing the armature/adapter clearance, I need more clearance between the armature and the solenoid. I think I'm going to take a thousandth or two off of the bottom of the armature to gain this. I'm not sure if this is the best place but it makes sense to me.

Lastly, I couldn't believe how much trash was in the one injector I've taken apart so far! There were bunches of tiny pieces of the disintigrated flat outer o-ring inside the injector. They were about the size of black pepper (big in terms of injector contamination). I couldn't believe that the engine ran as well as it did!

Evel486 · 03-14-2010, 01:47 AM

I don't believe in shims- I've seen them break down. The best place to grind is the top of the plate. The bottom of the plate and the top of the body must seal together. The correct clearance is .oo2" so grind .002 off the top of the plate. Measure the thickness of the armature plate, grind or sand the poppet valve mark off the bottom, then grind the top till you have taken a total of .002 off it as well. If you don't the poppet valve may not seal when the solenoid is energized. (The poppet valve must seal in both the closed & open positions)
BTW- that injector is an AA, not AO.

777funk · 03-14-2010, 09:12 AM

Quote:

Originally Posted by Evel486

I don't believe in shims- I've seen them break down. The best place to grind is the top of the plate. The bottom of the plate and the top of the body must seal together. The correct clearance is .oo2" so grind .002 off the top of the plate. Measure the thickness of the armature plate, grind or sand the poppet valve mark off the bottom, then grind the top till you have taken a total of .002 off it as well. If you don't the poppet valve may not seal when the solenoid is energized. (The poppet valve must seal in both the closed & open positions)
BTW- that injector is an AA, not AO.

Just curious where you got this from? The reason I ask is the solenoid top says:
AOxxxxxxxxxxxx

on it.

Also, most places I've read say .004" clearance is what is desired between the Armature/Adapter and also the Energized Solenoid/Armature. I've read this in probably 3 or 4 places. One guy said he measured a brand new one for his measurements.

But I'm just asking... I'm definitely a newbie to this injector and I've never had a brand new one in my hands.

**Excavator** · 03-14-2010, 09:23 AM

New is .004 in
min accepted is .0015 or better yet .002 in

777funk · 03-22-2010, 07:16 PM

Ok I had the top side of the Oil Adapter plate (highlighted in the picture) ground at a machine shop (2 thousandths taken off the screw side of the plate). Now I'm measuring Zero thousandths between the adapter and the energized solenoid. What can I do about this?

I put a shim between the solenoid and the spacer below it of 4 thousandths and that gave me the clearance needed. But can I fix it in this way permanently?