Ok so everything is together in the vert and it's time to start wiring the engine. I start routing/cleaning up the harness and I put it in the car to test if it will fire up. Well good thing I did because it doesn't fire up due to no RPM signal. If anyone follows my build thread they would know I had this issue before with the stock CAS. I purchased the FFE kit and it fired right up once I switched to the hall sensor. I have swapped everything into the new chassis the exact same way as before and I have no RPM signal again. I even bought a new sensor and it's still not working. Literally everything is exactly the same! I changed nothing about the wiring or settings in the controller and now I have no RPM signal. Please help before I destroy this ECU.

 

It sound like you have an intermittent connection in the harness. Check the DB37 for bent and damaged pins. I had a similar issue with a 1st gen several years ago and it drove me crazy. Finally tracked it down to a pin which had somehow become mangled.

If you have a scope, start at the CAS and scope the signal all the way down into the ECU.

 

I'm going to pull the harness and completely start over again with the wiring. Another thing that I did that is different from the last harness is I took the grounds from each harness (ms3/ms3x) and ran them into one inside the car. Could that be any issue?

 

Where on the car did you run your grounds from the MS? If you ran the sensor grounds anywhere but the MS itself, that could be an issue.

If you ran the MS grounds anywhere but the engine, that could also be a problem.

 

I am running the sensors through the sensor return on the MS3 harness (I believe it's pin 7, not sure) and the grounds from both my MS3 and MS3X harness are ran inside the car and bolted to a bare metal chassis ground. I figured out the issue though... Aaron was right and the pin for the shielded wire to the CAS was bent and not connecting inside the DB37. Straightened it out and the car fired right up! Thanks again for the help! And for everyone out there make sure you aren't forcing your connectors on!

 

What a pain in the ***, eh? I went through that as well with a 1st gen that would mysteriously run on one rotor if using 2nd gen ignition, but would run fine with the MS triggered from a dizzy. The harness was salvaged from a failed MS build (not my choice).

 

Yeah it was pretty annoying to say the least... If you didn't say to check that I'd still be cussing and pulling my hair out trying to figure out what was wrong.

 

did u just loose your rpm signal or rest of gauges as well?

 

It was just RPM signal from the CAS sensor on the car. Basically the male pins on the ECU, the one for CAS was bent and not sliding into the female side to make a connection. Straightened it out and it was all good.

 

While I am glad you found your issue, the MS should still be grounded to the engine not the chassis.

 

Technically wouldn't it be the samething? The engine is grounded trough the chassis so wouldn't chassis grounds be fine?

 

It is not the same. The engine is the main ground point for the starter. During crank the engine grounds to the chassis can fluctuate while the chassis in another part of the car doesn't. This can cause all kinds of odd issues with signals, especially the CAS signal.

Even when not cranking, I have seen people grounded to the chassis have weird things happen like coolant and air temp changing when the brake lights or headlights come on.

There is a reason why Mazda and other car makers ground the ECU at the engine.

Ken