injectors are solenoids, they need power and ground to open. Power is constant, MS provides the pulsing ground signal, you shouldn't be checking voltage at it.

If it clicks with the other channels, and doesn't with A or C, it's either an issue with the MS software or hardware, since you've already confirmed power is there and there's continuity from the signal wire to the MS.

launching into the circuitry of the MS is beyond my abilities though, hopefully someone else will chime in.

 

Thanks again for all your help. I've googled around a bit and found a number of people saying one or more injector drivers on the 3X card failed. This thread was interesting -- as a work around he moved INJ H to his failing one (D) by changing the 8 way ribbon to the expander card so he didn't have to change anything else.

Megasquirt Support Forum (MSEXTRA) ? Faulty MS3X injector output? (View topic)

I also tried measuring resistance of the various U FETs (I guess?), labeled U4 - U12 and got a different resistance between the two legs for the last and 2nd to last which seem to be more than coincidental. They were 19 KOhm while all the others were 42KOhm. All have the same part numbers so it seems like they should be identical. Here's what I'm talking about, U12 and U10 seem to match with pin 19 and 13 on the DB37.

 

I guess I'll check with DIYAutoTune and see if I can get a replacement or if they have other things to try.

 

ive built at least 100 ms3x's. never had one bad expander board. check your wiring harness.

 

I don't know what else to check. I have continuity from the ms to the injector plug signal wire. Pins 13 and 19. Power is ok at the injector with key on. Injector itself works. Is there a setting in tunerstudio I can check? Maybe it's software. The Gen settings have the sequence as a,b,c,d = 1342. Sequential on, fully sequential.

It's pulsing ground right? Maybe a ground connection problem I can check somewhere?

 

I was going to pick up a 'noid light' tomorrow, can I probe the output from the megasquirt with a test light? It should flicker when the output is working I think.

 

Hey I was looking at the back of the MS3X board and found a bridged connection on the pins of the small 10 way ribbon. Is this right or is this the problem? Seems to be pin 1 and 3.

Check this out:
Also there's a tiny filament stretched to the pin below (pin 2). I don't get continuity on that one though.

 

fix it.

 

FIXED. Amazing how well a car will run on 4 injectors. That was all it was, damn them. I spent so long making sure my own soldering was super clean just to be screwed by a sloppy job on the "plug and play" board.

Haven't done any tuning yet but really the car idles 90% as good as stock. Very small under-rev after blipping the throttle but even that went away after it warmed up.

Thanks for all the help guys!!!!!!