Bosch 124 interference

[thermaq]

Ive got ms2 v3 running a 4cyl Volvo 940. Until recently I used untimed injection, cause I used stock wiring loom which had 1 wire controlling all injectors, which worked fine. I
then redid the loom and routed all injectors separately. It still runs fine untimed, but when I switch from untimed injection to sequential, above 2500rpm my tachometer starts reading double than what I see in tunerstudio and I loose power. Toothlogger looks perfectly normal.

The injectors are high Z and as in a title I use Bosch 124 to drive a single coil. Signal to the Bosch module is supplied with a shielded wire (shield terminated at pin 3 of the module). Tachometer reads engine speed from coil's negative pin, which is the reason I think injector wires induce current in 124's input causing it to fire when it should not.

Does anyone have any tips on the issue? The weird thing is I don't even see anyone using shielded cable on tutorials showing how to use the 124 so is my module faulty if it's so sensitive to noise?

[thermaq]

Fix'd

To anyone using bosch 124: Connecting JS10 to IGN is not enough, like it's outlined here: https://www.diyautotune.com/support/tec ... 0-740-940/. You also need a pull-up resistor from IGN to 12v source (for example hole s12). The 124 starts charging the coil when it's pulled down and fires on upslope (hence "going high" in tunerstudio settings) from being released from ground. JS10 only pulls the output down and on the off state the output is floating and it needs to be pulled up, otherwise any voltage fluctuations are gonna fire it.

[bobxyz]

^^^ Don't do that. JS10 shouldn't need a pullup resistor. Adding one to +12v can stress the CPU chip on the daughter board (and might cause an extra spark on powerup). Are you working with a new MS or was it used in unknown condition? If JS10 isn't working correctly without the pullup you may want to change to a different pin for sparkA.

[Paul_VR6]

I don't think I have ever used js10 with a bosch module. Always use led w pullup and works perfectly.

[bobxyz]

One other thought - if your MS is wired up to include the internal high-current BIP373 ignition IGBT (not common), but is using an external ignition module, then an extra pullup resistor is needed. In this configuration, JS10 is NOT wired to IGN.
See Step 65 here: http://www.megamanual.com/ms2/V3assemble.htm#output