The car is all stock except the engine is a stage 2 rx7world reliability rebuild and a Pioneer head unit. The car has been ran with premix in every tank since the engine was installed. The issue is a CEL throwing the car into limp-mode. I pulled the codes and got 27 and 26, both are related to the OMP/MOP. Followed the steps in the FSM and checked the "Stepper Motor Resistance." Resistance was good on one side but shorted on the other side. FSM says to replace Metering Oil Pump.

I am planning on replacing the metering oil pump however upon reading some here on the forums, I have heard of the short in the pump shorting out part of the ecu. I looked a few steps further past where I was in the FSM and it says to check for 12v at the same terminals where I checked resistance earlier. If this test fails replace the ECU.

The OMP will be replaced however I am unsure about replacing the ECU. Are there any other tests I can do to ensure that the short in the stepper motor didn't harm the ecu?

Thanks!

 

replace the OMP and then see if it works

 

if you're premixing anyways you should delete the OMP from the engine but keep it on the harness, try removing it but leave it attached and see if it continues to throw OMP codes.

 

First, don't drive the car any till you replace the OMP with a verified working replacement. If you keep driving it, you will burn up the ecu.


Pull out the ECU, open it up and look for the burned traces. The pictures on the forum are very typical. Mine burned and looked exactly like the pictures.

Here is the best thread on the forum regarding this problem. https://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-mop-ecu-failure-diagnosis-710938/

 

you can remove the OMP and go with a Rtek 1.5 ecu chip since you premix anyways. This is what i went with, removes the OMP function of the ecu.
http://www.pocketlogger.com/index.php?pid=rtek7

 

my understanding is that there is a HARNESS ground that fails, and when it does the ECU grounds itself thru the OMP witch fries the ECU and OMP.

but the OMP can also fail on its own. so its a good idea to check the harness, if it checks out just do the pump, if it doesn't repair the harness too.

 

Thanks for the replies !

jackhild59 thanks for the link, I can't believe I never found that thread while searching... Maybe its because I was searching for OMP instead of MOP :\ I stopped driving the car immediately when the check engine light came on then checked the codes. Since it was the OMP code and I have been premixing anyways I drove it home ~2-3mi in limp mode and havn't ran the car since. I will look into the chip and deleting the OMP however I may opt to just keep the car factory.

Does anyone know if a FD electric pump will work on a FC?

 

Decided on the Rtek chip!

Took apart my ecu before sending it out, noticed some burn marks and a big crack on the MOP circuit..





Do I need to replace the ecu before chipping it ? There are no other visible issues on either circuit board.



Thanks!

 

You would have to ask the guys at Pocketlogger about that.

Personally, I would bet they wouldn't work on a burned ECU, even if it worked. These things get sold and traded around. They probably wouldn't want their name on a burned ECU. What if someone wanted to buy your 2.1 and wanted the OMP to work?

 

For those who were wondering...


Well I sent an email to the guys at Pocketlogger and they said " This damage is typical of a shorted MOP. With such a catastrophic failure, I would probably opt to get another ecu."

 

At this point you might look in the FS section. If you were to buy a 2.1 for under $500, you would be $ ahead.

 

I got super lucky. My OMP failed and I kept driving on premix for thousands of miles. Just turned off and restarted the car when it went into limp mode.

Didn't take my ECU out thank god!

 

I have been premixing with idemitsu, i was told to do to 200cc per tank. like every time i fill up. now that my omp is done for should i change the amount of premix? if so how much?

 

do u need a another ecu? i got a S5 NA ecu. let me know