Well i knew one day that damn pump would go out, but i didnt see it happen like this.
All of a sudden boom 16-17-18 afr's , oh hell what now.. ecu goes into limp mode nothing above 3k.








S5 TII

Before I go and replace it, I have a couple of Q's for the guru's here.

- What exactly causes this to happen when the omp gives in?
- Is the replacement from MazdaTrix the full unit? I dont see any electrical ...
- What are good replacement lines for the omp?
- OMP or Premix? What do?


Same exact problem here as well with topless7 back in '06.
https://www.rx7club.com/forum/showthread.php?t=529942

 

Nice Bricktop display.

On to your questions, I can't answer them. Haha

 

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-mop-ecu-failure-diagnosis-710938/

 

I tried replacing my OMP and CPU with some used units off of ebay and other sellers here parting their cars...worked for a month.

So I said screw it and just decide to get a working CPU and replace it with an RTEK chip that allows S5 to run without an OMP. Now I'm just premixing which, when all said and done, I think is a better route for a rotary.

http://www.digitaltuning.com/index.p...age=1&ecu=S5NA

 

there is a harness ground that fails and causes the ecu to try and ground everything thru the OMP which fries both.

if you put another ecu and OMP in it, it will do it again, you need a harness too; either fix or replace

 

better off just ditching the OMP and start premixing, it is better for your engine anyways.

the replacement new OMP is ~$1650(i usually suggest avoiding used for this reason), plus a replacement N370 ECU which is going to be $125+ due to rarity because of this issue and low production #s.

is it worth it? not really. it was a bad idea for mazda to ever even make it an electronic pump in the first place, there was nothing wrong with the mechanical S4 version.

perhaps sometime down the road i will dissect one of these S5 OMPs to see what it really is that fails in them as i have a bad one sitting right next to me.

 

it depends on what failed. the OMP is basically a drive by wire throttle body, its a stepper motor, with a position sensor, so either the stepper, or the position sensor can fail, or it could mechanically jam/fail too and that's just the pump.

when the ecu fries, its due to the harness.