no tach signal gm 8 pin

[Army of Six]

ok... MS2 v3.0 board NOW RUNNING v2.905

I used this ECU with v2.885 to control fuel only on a ford straight 6. it often had a noisy tach signal so i used a diode inline to quiet it down which worked. i have since pulled the ford straight 6 and dropped in a chevy v6 turbo charged with TBI injectors. the new motor uses an 8 pin small cap external coil distributor which i plan to use timing control to pull timing as boost comes in. i have tried every mod including the MK-HEI mod kit from DIY. i used the DIY nova project as my blueprint. that got me nothing in the way of a tach signal. so after searcing for a bit i stumbled onto the MSextra wiring that uses the d14 and d16. i wired that up and i got the motor to fire but ran very very rough. lots of bad starter kick backs even with the base timing set at 10deg (verified with timing light). i currently have my whole timing map set at 14 degrees. it seemed like the timing was erratic. i was looking on the laptop at some of my settings...i had the key "ON" but the motor wasnt running. i heard my fuel pump kick on..and off and on then noticed my injectors firing intermittently. i then realized that i was still running the v2.885 firmware. so i installed the MSextra 3.2.1 firmware thinking that will fix all my problems. since i have upgraded to the MS extra i cant get a tach signal at all. i tried the tooth logger in tuner studios and didnt register anything. with the 4 pin connector disconnected from the distributor i get spark.

UPDATED>>> i have since went back to the V2.905 with the MSnS-E modification and still absolutely no tach. would it be worth my while to replace the optoisolator at U3? i feel i have tried every mod out there to no avail

any help would be greatly appreciated!

Vic

[Matt Cramer]

Can you get an RPM signal on a Stimulator, or is it not getting RPM on both the Stim and the car?

[Army of Six]

well i dont have a stimulator. i do know that the datalogs are showing 0 rpm. i was very tedious with wiring it up..taking everything i learned from the first megasquirt install. i guess i will have to buy a stim.

[Matt Cramer]

Either that, or you could check the signals going into and out of the optoisolator with your oscilloscope.

[Army of Six]

i dont have an osciliscope....but i did order a megastim 2.2 yesterday. i ll post once i get the stim assembled.

thanks,
Vic

[Army of Six]

ooookkay..its official. i got the stim today and assembled it. earlier i decided to get back to square one with the input circuit. so currently i am running just like it says in the 3.0 manual...

"On the V3.0 main board:

use the 'Hall sensor circuit' (step #50 in the assembly guide),
jumper OPTOIN to TACHSELECT on the bottom side of the PCB, near the DB37 connector, opposite the heat sink,
jumper TSEL to OPTOUT on the bottom side of the PCB, near the center.

jumper JS10 to IGN (this uses the processor port for the outgoing timing signal directly),
jumper XG1 to XG2 on the bottom side of the PCB, near the 40 pin socket, "


with the sim hooked up i get measurements with CLT, IAT, TPS. but nothing with the O2 or RPM
the only LED that is on is the IGN.

so...please....where do i go from here?

[Army of Six]

whoa..lol. i forgot about the 2 switches next to the rpm and O2 pots. so i am now getting RPM with the stim as well as reading for everything else. still currently have the board set up per the manual 3.0 board as mention in my last post. but i am still showing No rpm when hooked up to my GM HEI 8 pin.

[Army of Six]

hooked the ECU back up to the motor but ran a wire a tach new wire from distributor to the relay board and grounded the ground wire from the distributor to the motor instead of the sensor ground on the relay board. i do get spark with the Vref disconnected (verified with a timing light) but still no rpm at all.

[Army of Six]

well...problem solved i guess. it looks like the ebay special aftermarket distributor was inferior to the stock junkyard distributor. i just installed the junkyard distributor with the hall effect GM set described in step 50 in the assembly guide. now i have a good clean tach signal. best 40 bucks ive spent so far. but now i have another problem ....... see post viewtopic.php?f=89&t=41420