Above picture is an injector AFTER cleaning, the "normal way" (without disassembly) with solvent, carb cleaner, compressed air, etc. Not too clean after all that.

I recently opened up a few S1 oil injectors to see if I could fix the vacuum leak they all had. I will need 6 soon for a "magnificent" budget build and was not interested in spend $60 a whack, even at Mazda Motorsports prices.

I ground the crimp off of the top by the air nozzle and found the diaphragms all in good shape. Even pre-cleaning, the valve module inside the injector both held vacuum and flowed well like it's supposed to.

The problem in all cases was a hard plastic internal sealing ring, that was probably an o-ring at some point, but was now fossilized, and leaky.

I cleaned up the valves and the injector tubes, put the unit back together with a thicker o-ring and pressed it together in a vise, while epoxying the top back on. Ugly but workable.

I fixed all of them this way. Some leaked more than others, and it was the o-ring in all cases. They were all from a few different engines, with different mileage. Some had the extra notches in the hex, and some didn't. (early revision ones I assume.)

Just something to try before you shell out big $ on injectors.

 

bump for pix added

 

As I did a comprehensive study on them they are not cleanable. The irony, the cleaning product even damages them.
The best is to use those with a line on the hex ( I believe there are 3 revisions and those with a line have better inner plastic parts).
My car 2005 had no line on hex version and on initial testing one of them on the front rotor had immediate fail and on front rotor had a slow leak, after some cleaning and working around they become good. BUT the next day I did check and both failed!!
https://www.rx8club.com/series-i-tec...-macro-271354/

You could put thread the inner section and make them serviceable, which is too much hassle if you ask me, some times you could find them very cheap on eBay.

 

Well, thank you for your reply, but I disagree. I read your study and posted there as well at the time. I did not agree with your idea of putting another check valve further upstream, but I didn't state that at the time. That is why I looked further at this for my own build in my second RX8.

Over time, I have accumulated about 20 of these injectors from junkyards and ebay of all different vintages.. I have tried to clean them all without taking them apart, and had some success, but also observed what you stated, that after a while, they would leak again. Once I took them apart, cleaned them, and replaced the o ring, no more issues. Time will tell, but I believe based on my own "study" , this is a fix that will last for many miles.

To see if I was missing something based on your study, I connected the first one I fixed this way to the vacuum port of a four stroke single motorcycle and put a couple of hours of use on it. The vacuum pulse on this engine is very aggressive, which may have given different results, but I don't think it would give me an artificially favorable outcome, if anything, such an aggressive pulse would reveal any weakness in the membrane valve. That first injector worked the same before and after my test.

In addition, I believe a marginal membrane valve could be fixed at least for a time, by "preloading" the spike that mounts it inside the valve body, to draw it closer to the valve body to seal better if it is warped too much or too floppy.

I will report back after these injectors are installed on an actual RX8 engine, but I see no reason at this point to expect premature failure. Perhaps the cleaning solution you used damaged the membranes irreparably, and the stuff I used did not. The membranes don't appear to be especially fragile, based on what I am seeing. The o ring is not made of the same stuff, and varied greatly in resilience in all the injectors I opened, but the membranes were all very similar in condition. Therefore, based on that, I determined the o ring is the major issue, not the membrane.

 

Well Mr. Kenichi Yamamoto I have to say I never propose to add an extra one-way valve. actually what would really work is adding numbers of check valves.
Oil injectors never experience any negatative pressure aka vacuum in form hos end (brab fit). However, they would experience positive and negative pulses from the thread( in housing) side.
The Mazda manual check with vacuum pump test is the easiest way to check them in situ rather than removing them.
If you don't have hand hold vacuum pump to check them you can never confirm they are working in the first place. As my memory served they should hold vacuum for a few min and some drop is still actuatable.

What did is to put a long silicone hose on each of the oil injectors to separate the pules as well as make it easier for future testing and will vacuum test them on each oil change.
The OEM hose layout is very difficult for vacuum testing besides being short to 4 to 1 section. So, a long equal length hose was my solution apart from cleaning them with liquid paraffin and upgrading to those that have a line on the hex part.

What that OEM check valve design does is to prevent oil to back to the line on positive puls cycle besides proving air as a stop mechanism to equalize the pressure of housing suction on vacuum cycle of the oil injectors.

 

Yes, I know how they are supposed to work. My name is not Yamamoto.

Again, it was the o ring, not the membrane (which looks like Viton and seems quite rugged) which had failed. It is a simple and inexpensive repair for those who wish to undertake it.

 

Sorry about the name. Your profile is Yamamoto though.
Just last question, did you try them by vacuum pump for 5min ?

 

Yes his name is Yamamoto.

I did test them with a Mityvac, and they all held vacuum for hours. Overnight, really. They went from all being very inconsistent in vacuum retention to being more or less equal in seal.