Bench Testing Questions - 16197427

[Thainglo]

I'm planning a TBI conversion for my 78 Corvette and have gathered up a couple of 16197427's to learn on. My plan is to use a JimStim that I had from building a Megasquirt as my primary bench test tool. Yesterday I wired up the PCM to the JimStim terminals following the pinout diagrams and schematics from this site.

Here is my basic setup. JimStim at the lower left, plus I've got an ALDL-USB cable to read the serial port. Please excuse the wire nut holding the grounds together, I'm using that temporarily until I get things sorted out, then will do a proper solder/heatshrink.
image33.jpeg

My expectations when I applied power to the JimStim would be that the LED indicating fuel-pump relay activation would light up for 2 seconds, as the pinout directions indicate. The PCM is receiving power through its battery line (orange) and the ignition on (pink/black).

When I turned on the JimStim, nothing happened. No fuel pump LED indication and no connection showing on TunerPro RT through the ALDL cable.

Trying to simplify it further, I bridged A & B terminals and ran the MIL wire to an LED. My thought was that it would at least throw plenty of error codes (no transmission lines connected to the JimStim). No flashing lights for the MIL when power was applied.

Is there anything I'm missing regarding waking up the PCM? The two units I pulled are both from the local pull-a-part, so condition is unknown. However, I wanted to check in before trying to hookup the second PCM in case I managed to let the blue smoke out of the first one. I did disassemble the case to look for any pre-existing damage (scorched components, broken solder traces, etc), but the unit itself looked brand new. Doesn't mean it is working, but at least it has not suffered any egregious damage.

Any thoughts? I'd greatly appreciate any guidance. Trying to learn all this stuff and have been doing TONS of reading on this site, thirdgen and others. I'm exciting to get into the nitty gritty of it now, just don't want to start installing into the car until I know I have a working unit.

Thanks for any help!
Matt

[Thainglo]

Made great progress today. I unhooked everything but the power and grounds, then hooked a LED into the SES line. When I powered up the jimstim again, the SES light went on and flashed codes when I jumpered A and B terminals. Success! Hooked another LED into the fuel pump signal. Sure enough, came on for a couple seconds when I turned on the PCM

My first issue was the cable I was using. Dug out and old cable I'd built pre-FTDI days, once I recalled how to hook it up, worked great. Was able to get several of the gauges to work on the digital dashboard in Tuner Studio.

Not sure how to wire up the tach signal to the PCM from the jimstim. Anyone have any ideas?

[Thainglo]

Some further reading on DIYautotune helped discover the purple/white wire needs to be fed into the tach line on the JimStim. As soon as I did that, the tach display read out perfectly. Big step towards installing!

[Thainglo]

Here is a quick vid I shot of the bench testing in action,must in case anyone is interested in replicating. The JimStim made it fairly easy. Cool to see it fire up after being pulled from the scrapyard.

https://youtu.be/JJu-E_ldvKU