I am in the process of buying a 1990 fc rx7 with a bad OMP. I have done a decent amount of research and have a couple questions regarding what you all would do.I have learned from many forums that the S5's ecu freaks out when you disconnect and blocking off the OMP. I also read about sending your stock ECU off to Rtek to add a new chip, but unfortunately they have gone out of business. So, now that leaves me with a couple of questions on how i should move forward.


Should I block off the OMP, buy a new one to plug in and zip-tie to the frame? this would enable me to be able to keep the stop ecu & premix with each fill-up.


Or


Should I just buy a re-manufactured OMP and replace it?


Is there a way to rebuild the OMP?

I am learning still and am open to all suggestions.

 

It depends on the intentions of the car. Daily driven? Driven maybe 2-5 times monthly? My car HAS a working OMP but it's fastened near the passenger shock tower and the area is blocked off on the front cover. I drive the car about 1500 miles yearly and premix every fill up.

-M

 

I am looking to restore it and possibly be able to daily drive it. I want it to be as reliable as possible.

 

My advice is to replace the OMP in original location, but if never serviced, the lines should also be checked as they may need replacement.

 

OP - How do you or the guy who owns the S5 FC you're looking at know the OMP has failed? Is the car running in "limp home" mode now, and if so, has anyone read the ECU's MIL codes? If you have, and if you're reading a code 20, 27 or 37, that tells you it's an OMP problem, but keep in mind that doesn't always mean you have a failed OMP. More than likely, what's going on is you have an intermittent electrical connection issue with the wiring harness (open or short). Keep in mind these stock S5 FC wiring harnesses are all over 28+ years old, and that age + use/heat cycles takes its toll on wiring.

 

In my (limited) experience, the OMP is actually pretty reliable.
I agree about the possibility of wiring issues and very emphatically agree with checking the hoses, which are ancient and brittle plastic by now.
The system always seemed like a last minute addition to the engine package but once renewed (including vac lines), appears to work just fine.

 

The previous owner told me that is threw a code 26. which means the oil metering pump step motor has failed right? therefore needing to be replaced. It does go into limp mode at around 30 mph.

Is there any company that will re-chip the stock ecu like Rtek? That seems to have been the way to go when deleting the OMP and premixing. which is what I would like to do...

Do any of you have a extra working OMP for sale?

 

Yup, I missed code 26, which is the code for OPM stepper motor (output device). But that doesn't necessarily mean the OMP is bad - it still could be a wiring issue. You need to troubleshoot the wiring first before throwing new parts at it.

Not that I'm aware of on the 1st question. However if you want to switch to an aftermarket ECU and fabricate a new wiring harness, there are several ECUs that can be setup to drive the electronic OMP.