Electrical problem with my 2016 DF150 (voltage spikes or bad SDS connection?)

[supagruv]

Hello all! I got a copy of the Suzuki SDS software (v8.5 and running Windows 11 on a new LG laptop) and connector cable from eBay and it works great... up until I start the motor. Then it seems there are constant voltage spikes (and other STRANGE electrical readings). I complained to the eBay seller and they sent a new cable but the problem persists. I've done every kind of troubleshooting I can think of with no results. The list of what I've tried so far is below:

1. Bypass main power switch and connect outboard AND white wire directly to the new Interstate battery.
2. Run a new white wire connected directly to the starting battery
3. Use different OBD2 cables
4. Connected on COM1 (but also tried COM2 and COM3)

The voltage spikes aren't the only issue. Every 5 or 7 seconds it seems all of the numbers in the "Engine Data" section seem to go crazy. For example the Battery voltage will go from 14.4 to 13.9 to 16v. The Fuel Inj Pulse Width will go from the normal range of 3116 us to something like 110000 and then the Injected Fuel Amount will go from 18mcc to 8208mcc. The Throttle Position will go from 0 degrees to 61 degrees as well. And then after several minutes I get a "Communication Error" dialog box and the SDS needs to be reconnected. If I connect a multimeter to the white wire on the engine and ground by the starter then there are no voltage spikes seen or anything like that.

The motor runs well with no error codes. I've only had it for a short while and put maybe 10 hours on it. There is another fuel obstruction/starvation issue I'm troubleshooting as well but at this point this seems unrelated (I have another post regarding that issue causing it to intermittently bog down and sometimes not even go more than 2 mph).

I'm feeling like I may have a possessed outboard at this point... first the drive shaft splines were seized and had to remove the powerhead and replace the drive gear. Then a fuel issue of some kind... now this. A "ghost in the machine" or something...

I've got an appointment with the local mechanic/dealer in a couple weeks (been waiting two weeks already). Just hoping to get to the bottom of things before the $100+/hr kicks in.

Any thoughts you have would be greatly appreciated. Thanks!

Screenshots below:

Dropbox link: https://www.dropbox.com/sh/bmg087hya...kRTmQETMa?dl=0

[redlowrey]

After reading this definitely run a separate power and ground on the fuel pump I wouldn’t mind betting the computer is not Grounding the fuel pump. Because you have a lost ground on the engine.

[redlowrey]

I should have added all these engines have a capacitor on the main battery feed to filter emi or electrical noise if it has failed it may not be filtering out noise, if it shorts it will blow a fuse.
Also if you have a shorted diode in the rectifier it will allow AC to sit on the DC and that alone will upset digital signals in the computer, especially seeing the computer controls the ground on the fuel pump circuit.
Do you know how to use an oscilloscope, that would be the easiest way to look at AC ripple or noise, if not put your multimeter on AC and connect it to the rectified output of the regulator and ground and you do not want to see more than 300mv of ripple.

[Freddy jakob]

Hello. Did you find the fault in the engine? Sorry my English. I'm from Norway.Regards Freddy