RB25 no rpm signal

[mschlang]

I am working on a 240sx with an RB25 swap using an MS3X. None of the outputs are connected yet, just trying to get the inputs figured out. We seem to be seeing the correct cam crank signals, yet are not getting an rpm signal.

Crank signal is wired to the mainboard pin 24 with a 5v pullup from the proto area to tachselect. Cam signal is wired to MSX pin 31 per the DIY tech article. 5v pullup for the cam is pulled from mainboard pin 26.

The CAS is being spun with a drill at approximately 1000 rpm for testing. We have verified 12v and ground at the CAS plug, both cam and crank show 5v at the plug. We tried adjusting the VR pots on the mainboard and MSX with no change.

I guess the big question is, how is a signal being show in the composite logger but not making it through as an rpm signal? We saw no activity in either the tooth or trigger loggers.

Thanks!

[mschlang]

Also, I noticed a few differences between the DIY directions and those in the mega manual.

Pull up resistors: DIY=1k ohm, Manual=330 ohm
Ignition capture: DIY = Rising edge, Manual= Falling edge

DIY mentions "Spark output: Going High / Inverted if using stock ignition module", no mention in the Manual (though this shouldn't affect getting an RPM signal)

Manual mentions "Flip polarity on hi-res should be set to "Inverted"", not mentioned on DIY's site

[Matt Cramer]

It looks like you've got the CKP and CMP backwards.

[mschlang]

Thanks for the reply Matt,

I tried switching them last night, still no rpm.

Could any of the differences I noted be creating an issue?

[Matt Cramer]

Generally, using either directions 100% should work. Can you get a new composite log with the signals flipped?

[mschlang]

Ok, I flipped the CKP and CMP, the log is attached below. After doing this and seeing a usable signal, we put the CAS back on the motor and lost the signal. Turns out the CAS only operates correctly when spinning CCW, not CW as the motor does. I didn't think this was even possible for a hall sensor?

[mschlang]

It runs! In addition to having the ckp and cmp backwards, the cas disk was upside down. It had a 24 tooth replacement disk as the AEM that was installed couldn't deal with the stock 360 hole disk. We tried and tried to get this car running on an AEM pnp, looks like that ecu is going to be someone else's problem!