Hey everyone,

I realized that there were not any up-to-date guides with active photo links to diagnose, remove and replace the OMP on S5 FC's. I decided to take some photos to help you on your journey of fixing this issue on S5's specifically because you cannot bypass the OMP as easily as the S4 mechanical OMP.

Background:

I drive a 1989 Rx7 Convertible who for the most part has been problem free. The car was stored in my storage locker for two years as I had other priorities that took precedent over my ability to drive my car often. The fuel pump died from sitting as I parked the car with little gas (oops) so I had starting/drivability issues. Once I replaced the fuel pump the car ran fine, I drove it for a bit and then decided to park it at my house so I can drive it more often this summer. The first day I decided to drive it after having no issues for a week was plagued by limp mode conditions, lack of power and inability to push the car past 2000 RPM along with a flashing light when attempting to accelerate. The car idled perfectly fine, no check engine lights upon start up or idle and even driving under 2000 RPM there were no issues. The car would sputter and shut off as soon as it hit the wall in RPM, but you would be able to restart the car just fine with no check engine light and the ability to limp home.

Now, being a Rx7 owner, you know a few things such as that the FC came with a very rudimentary check engine light code system. I do not want to get into all the details on checking the system, but it is as simple as jumping the diagnostic connector under the hood near the coil pack and battery box. I will attach a link to FC3SPro that has a helpful easy to follow guide.

https://fc3spro.com/TECH/HOWTO/ERROR...KI/kerror.html

Now, after checking the codes only one was popping up, code 27, two long flashes and seven quick flashes. I know it is a pain to follow the flashes, but this has been the easiest way to find codes on any car without an OBD plug. Code 27 is a general OMP/MOP code. For a week or two I tried to research as best as I could what could be the cause as I have never had issues with my OMP before. Most threads and posts were saying the worst, the OMP is dead, or at least the sensor on the OMP is dead. The sensor is not available separately. The other few threads I read were saying the OMP is "stuck" and needed a love tap to unstick itself. For a few days I tried every method available online to bypass the dreaded OMP replacement.

Nothing worked, and I was left with only one option, buy an OMP and replace it. Surprisingly Mazda still stocks many FC parts and continue to produce more due to the program they run in Japan to restore FCs via the dealers. Anyways, a new OMP was out of the question as the part new from Mazda was over $4,000 after tax. Here is a screenshot of my mini heart attack:

So, as you can see, buying a new part that is worth 1/4 of my car was so far out of the question it was not even worth debating. I decided to look for used, this was like finding a needle in a haystack as I just could not find anything near me or online, there was one eBay listing that had one for almost $1000 + shipping. I was feeling defeated, tempted to tow the car to storage and worry about it in the spring. Lucky for me though, I found a local seller that had one for less than half of what eBay was going for. I bought it and decided to try to replace it that day but decided against it as it was getting dark and I did not want to push it and end up breaking something. I had an idea though, I disconnected the plug for the OMP which is beside the alternator, and plugged in the "new" OMP, the car started right up, and I wanted to see if the pump was faulty as used is at least 33 years old if it came off of a 1991. This is not a long-term solution as you need to remember to premix as there will be no oil being injected during this test. I then decided to do a quick drive around the block to see if the RPM limp mode wall was still there... the car easily pushed past the 2000 rpm wall and it felt great, no engine lights, no stuttering etc. I made it home, parked her, and decided to attempt it the next day.

The next day I decided to try my luck, fearing the OMP lines would be brittle and break which would mean an entire teardown of the intake tract. I also did not think to take photos until I was already halfway through the process so most photos I had take during installation.

Here you go, I will try to give a brief description between photos and things that made it easier for me etc., beware this is photo heavy.

Do note, the basic process that I did not photograph was the disconnection of the battery, you are working with electronic components so please disconnect the battery in advance to ensure there is no charge going through your wiring harness.

You are going to have to remove the airbox obviously, this is very straightforward, there are three (3) bolts holding the intake box to the car. Remove all three bolts.





Once the bolts are removed the intake box will be able to be moved around slightly, remove this snorkel connection rubber piece by moving the intake box slightly and pulling.



Next, unplug the MAF/AFM connector, this is towards the rear and bottom of the airbox. It can be unplugged with the airbox still in the car. A long screwdriver helps to pry the connector while you push the button as you NEVER want to pull from the wiring.



Here you can see the AFM/MAF connector disconnected, move it to the side/under the airbox.



Loosen this Phillips head band clamp, this is to loosen the intake tube from the intake elbow connected to the throttle body.



Make note of this hose, this hose goes to the air pump, disconnect it here. I used a pair of pliers and wiggled it, simple enough.



The intake is almost ready to come out! you are 1/8th of the way there. These two hoses must be disconnected, it is easier to disconnect them from the intake neck, but sometimes it gets stuck and accidentally gets unhooked from the other end on the engine. Either way these need to be disconnected. On mine, the shorter hose came off from the engine and the longer one stayed on the engine. Remember and note the placement in the intake neck.




The time is NOW to remove your intake box, go ahead and gently remove the box with the AFM/MAF connected, try not to bump it or bang it against anything. You may have to wiggle it out as it is a tight fit.

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Fun fact, this is the fuel pump jumper underneath the airbox, this is the connector you need to test if you think a component in your fuel pump wiring is fault as this bypasses all of those points of failure to test if your pump is functional. DO NOT leave this connector jumped and drive with it in...



You can see here where my intake hose disconnected from the engine on the shorter stubby hose, and the longer hose stayed attached to the engine.




Here you can see the wiring for the OMP snaking its way through the air pump, which is the next thing to remove.



This elbow I am pointing at is the stubby hose that goes directly from the airbox to the air pump I mentioned earlier.



To remove the air pump, you need to remove the belt as well. This adjustment bolt needs to be loosened to swing the air pump down and remove the belt. The other bolt in the next photo may need to be loosened to achieve this.





With the belt moved, this is the bolt that needs to be fully removed to remove the air pump, this bolt is VERY long and be mindful of the U-shaped washers the space out the pump and bolt correctly. Take note of how they go back properly.



Almost forgot, the air pump has a second hose, this one goes to the engine itself, I did not realize it was there until I remove the pump itself, and it came along with it.



Here it is disconnected from the air pump.



Here it is accidentally disconnected from the engine itself... it was a serious pain to get back on and you will see why later.



Once you remove the bolt, the air pump needs to wiggle out as the rusty U-shaped washers are stuck sometimes. Note how long the bolt is, the threads are short, but the bolt is long and hits the fan slightly but comes out without removing the fan etc.



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Next, you need to remove the adjustment bar for the air pump belt... you will understand why on the next photo...



Because the OMP/MOP lines and wiring harness run through a hook mount for them. You could bend it as I did to carefully, and I mean CAREFULLY move the lines out of the way so you can fully remove the bar to get at the OMP/MOP. Any rough movements, and you will snap your lines and be throwing your tools in your garage. You can see that mine are old and stained looking, luckily for me they are not brittle, and I did not crack them.

Also note, the lower radiator hose is pictured, most threads I read said that you need to remove it, I did not as there was ample room and I did not want to collect the coolant. Save yourself the step.



Disconnect these two white connectors, this is the wiring for the OMP/MOP. Do this prior to the next step as the decades of heat has made them a pain to pull off, again do not pull from the wiring.



Unbolt this bolt that holds the connectors for the OMP/MOP, Mine came with it on the "new" one and it is a pain to disconnect the connectors while attached to the car. As you can see the bolt is an alternator bolt and only needs to be loosened to slide the bracket out.



NOW, is the time to look at the monumental pain in the *** that is the worlds most expensive rotary part. A couple of things of note, at the top of the photo you can see one of the OMP/MOP mounting bolts, remember this as I forgot to take a photo of this bolt on the right side of the part in subsequent photos. Next thing to note is that each OMP/MOP line has a washer between the BOLT and the Lines as well as another large washer between the lines and the OMP/MOP. I almost forgot and lost the washers nearest to the bolts, do not risk it, put a rag underneath to prevent loss of washer. Finally, take a mental note, photo or sketch to remember which line goes to which opening. I had to look through my photos to verify as if they are mixed up, they will inject at wrong intervals.



Here is a closeup of the bolts for the lines that go into the OMP/MOP. You can see that you cannot use any regular bolt as they have openings for the oil to pass through. Also note that the washer is correctly placed on the bolt prior to installation.



Here is the other washer on the backside of the oil line hoses. This mounts between the lines and the OMP itself. I do not know if it was from the factory but make sure you orient it the correct way as mine was warped/dimpled in towards the OMP. This is to prevent further leaks.



Here you can see the bolts and lines disconnected from the OMP, also note I almost lost a washer as you can see, they get stuck to the lines and fall off.



These next two photos show the left side of the OMP/MOP, and the other two bolts needed to be removed. There are THREE in total, two on the left closest to the engine, and the one I previously mentioned on the right side in a previous photo. Do NOT unscrew those screws as they are just for mounting the solenoid to the OMP itself and will do nothing but give you a headache.




This photo shows the bottom bolt spot for the OMP/MOP, note that this bottom hole is for the longer bolt which you will see in the next photo.

In this photo you can see that the three (3) bolts that hold the OMP/MOP are two different sizes. One is for the bottom left hole, and the two shorter ones are for the top left and top right hole.



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Mazda really thought of everything... built in bolt and washer holders.

Once the OMP/MOP bolts are removed, the OMP can be wiggled out with a little effort. Note that you need to be careful of the brittle lines when attempting to remove it. Also note that the OMP has a female slot on the engine, and a male slot on the OMP itself. You will need to align these properly when installing the new OMP. Also, this would be a good time to install new o-rings on your OMP if yours did not come with them. Mine were new so just replace them on the OMP as needed.




Installation is the reverse, again the photos may show various states of disassembly, I had to take photos upon reassembly to get this guide completed. If you have any questions feel free to ask. I thought it was going to be an intimidating daunting task but it took me an hour to go from start to finish. The hardest part was finding a working OMP/MOP.

I think the only mistake I made was installing the air pump prior to installing this piece that I said would come to haunt me at the end. There is no give in the rubber anymore and with the air pump installed you could not put it back on.



Uh oh, Mazda is calling the police on me because I removed the air pump...



Many different threads talk about removing the fan and shroud, but I found this way easier and I did not have to remove the rad hose like other threads as well. Oil loss is minimal so a rag will suffice.



And this is the bad boy that causes so many S5 owners to have a stroke...