Fixing tii injectors

[dlacey]

I have always wondered how difficult it can be to fix these injectors... below I show that you can fix spray with valve grinding paste in a few minutes... the issue of opening pressure more difficult to address..not so much because the spring has stretched but because it has worn grooves in the little 'peg' that tensions the spring...if only there was a source of new little pegs...

 

[BarrettN]

I'd been thinking that lapping the pintle would probably help. I have access to a milling machine, if I end up machining new pegs I'll let you know.

[conkitchen]

Shucks! That pin could be made with a drill press and hand files if that is all that really needs replacing.  Looks like a good cleaning and and "hone" should bring one back to life.   

 

The spring itself is the heart of the functional body.  If that's toast, perhaps McMaster Carr has similar, but that would take some researching.  

 

but what do I know. 

['76mintgrün'02]

1 hour ago, conkitchen said:

Shucks! That pin could be made with a drill press and hand files if that is all that really needs replacing. 

 

I'll bet the original pin is hard enough to ruin your file (and a softer one would be a short lived fix).

 

 

[dlacey]

4 hours ago, '76mintgrün'02 said:

 

I'll bet the original pin is hard enough to ruin your file (and a softer one would be a short lived fix).

 

 

Yes I also think all the parts here are specially chosen materials...to operate at 50-100Hz and through 10's of millions of cycles...

I wondered about grinding  down a HSS drill shank to make a substitute spring peg....should be hard enough material but challenging to shape in my shed.....

[JsnPpp]

44 minutes ago, dlacey said:

Yes I also think all the parts here are specially chosen materials...to operate at 50-100Hz and through 10's of millions of cycles...

I wondered about grinding  down a HSS drill shank to make a substitute spring peg....should be hard enough material but challenging to shape in my shed.....

 

Feels like any heat-inducing metal work adds risk of annealing the metal, so unless grinding is performed carefully and with frequent water baths, it may end up the same situation. In a pinch though, why not.

 

My first thought is surely Bosch (I think they are Bosch?) made injectors for multiple engines and tried to share parts where-ever possible... so I wonder if that could help the search.

 

Looking on ebay and folks want a lot for a set of injectors these days.

 

Jason

[iinca]

new springs would be a gift from 02 heaven. I just want the factory pressure back for starters

[BarrettN]

@dlacey The Chemico paste you used, did you use the fine or the coarse? If the fine, did you feel that an an even finer compound would work or be desirable? I have to say that made a really nice improvement to the spray pattern. Did you do the lapping stage in steps, checking as you went, or were you able to to do it all in one go? Does the time in the video approximate the amount of time you spent on the lapping process? 

 

Thanks, 

 

Barrett 

[dlacey]

Hey Barrett,

 

I used the fine paste only...it still felt quite 'gritty' for this job... trying to be delicate I tried using a fine metal polish first...but that didnt seem to have the guts to clean-up the sealing surfaces - and on my first attempt made almost no difference to the spray pattern. This injector has been dismantled and thoroughly cleaned before...so the original bad spray pattern is not just dirt & crud..it really is that the pintle doesnt seal. In that 'before' spray there's no 'static pressure', all the pressure leaks away as the injector dribbles. 

 

I ground the pintle & faceplate for around 2 mins...by hand...similar style to how you'd do an intake valve on a cylinder head, no huge force - just rotating my grip on the pintle and lifting it off the seat to get some fresh paste on the sealing surface. I believe that finishing-off with an even finer paste would help.

 

The spray pattern after is really even and there's good static pressure... i dont have pressure figures as my pop tester has a 15,000psi gauge...i am swapping it for a 1000psi gauge so i can get some opening pressures and leakdown numbers.

[BarrettN]

Thanks for the details on this - through having a couple of "the price is just too good to pass up" and "ok, that deal I thought that was going to fall apart didn't" I've ended up with in addition to my car two additional pretty complete intake setups. Counting my car, I have 18 injectors  , so I'm interested in getting them right! My injector with the absolute worst performance is my guinea pig, I'm going to pick up some valve compound and see what I can do with it. My pop tester has the pressure gauge swapped out for one that will let me put some numbers to the results.

 

From what I found the Chemico fine is 200 grit - I'm looking at this site that sells 80,180,320,400,600,800,1200 grit compound (Clover\Permatex) in 2 oz size amounts - https://www.ezbore.net/Valve-Lapping-Tools-s/1830.htm. Based on your remarks maybe I'll get the 320 and the 600 or 800 and see if doing a second pass with the finer compound is worth it.

[BarrettN]

OK, so today's mail brought me valve compound in 400, 600, & 800 grit, I plan on getting to playing with them this weekend and we'll see how it goes. 

[dlacey]

I fixed my pop tester gauge and, as expected, although I have a nice spray pattern, my opening pressures are in the 180-220 PSI range.

 

I had an idea to recover the spring tension...this is lost as both the pintle (light blue) and Spring Peg (yellow) wear over the years...the spring is slowly cutting though those parts... we talked about re-making the peg..its a complex small shape...certainly beyond my capabilities to make accurately.

The way the injector is built includes a washer (red) 8mm ID, 12mm OD that is compressed between the green check-valve and the blue body of the injector. The yellow peg sits inside this washer, bearing on the pink sleeve.

 

I thought that I could try switching the washer for a hardened 6mm ID, 12mm OD washer so that the peg could bear upon it instead of the sleeve.. (right diagram, red washer)... that would have the effect of raising the peg and increasing the spring tension...that should restore the opening pressure....

 

I ordered some HSS washers...

 

Edited May 29, 2020 by dlacey

[resra]

This is awesome work. 

[BarrettN]

I think in addition to the wear due to the spring wearing into the crossbar and the pintle, there's also going to be some wear of the actual pintle itself and the seat, especially since the lapping just wore some of it away in addition what has already worn. Interesting idea about using the washer with a smaller ID. I haven't been sure what steel they're made of, I'd have thought that they'd be more of a mild steel given they seem to seal the injector. Honestly, I was surprised  that they weren't copper, but my knowledge is limited in these things. I think wear versus sealing might be an issue with the washer composition, although the trade off of having to replace the washer every few years in exchange for good opening pressures is a trade I'd make all day long and twice on Sunday. I don't think the reduced washer ID would restrict fuel flow, but something to think about. If the full washer thickness is too much, I could see machining a step into the washer to get the pressure just right.

 

I'm hoping I can get into work where I have access to a nice lighted Leica stereoscopic microscope - I'll be able to get a really good view of everything and hopefully be able to get a good estimation of how much of reduced opening pressure is due to wear, and how much is due to spring fatigue.

 

At work I do have access to a CNC milling machine and CNC lathe, I can talk to the pros there about what it would take to fabricate a big batch of crossbars, maybe even do some of varying offsets. Sure wish I had access to spring winding equipment!!

[dlacey]

4 hours ago, BarrettN said:

there's also going to be some wear of the actual pintle itself and the seat, especially since the lapping just wore some of it away in addition what has already worn

Agree: 'good' injectors have the flat suface of the pintle clearly proud of the faceplate, i have some other more worn ones where they are at the same level - the pintle resting deeper inside the injector...these are really end-of-life... not every injector can be saved.