I've posted already a couple of times about my sparkless 740 (B230K with rare
EZ100K system). I'm checking it over a little more carefully as I'm
completely stumped, and find that the 5 volt parts of the ignition electronics
(i.e. the blue signal wire on the hall sensor, the trigger wire leading from
the ecu to the power stage, etc..) are in fact running at 3.7 volts (I should
have been more careful reading my analogue meter - it's pretty much 5v on the
AC scale not DC - doh!). I swapped the ecu for one off of a B230E
engine - EZ118K - and still saw 3.7v. I'm guessing then that the 5v parts of
the cicuitry are derived from a separate voltage regulator not onboard the
ecu. Is that right? I'm guessing that if I'm only generating 3.7v pulses from
the ecu that these may well be insufficient for triggering the power stage and
hence explain why I see no spark.

Any ideas as to why I only see 3.7v at the hall sensor, ecu, ... and how I
can fix this?

if it is a signal line, it is normal, DC measure is the average voltage of time
could be anything between 0-5V

No, I'm seeing this at the blue wire on the Hall sensor connector, which
should be a flat 5v, and when I toggle the blue and black wire on the Hall
sensor connector I'm seeing a 3.7v signal of about a second duration at the
signal wire (pin 5) of the power stage connector. The 1 second duration is
about sufficient for my (admittedly crappy) analogue meter to settle down and
allow me to read the DC voltage. Sorry if I was a bit unclear on that.

cheers
Tony

My first thought would be corrosion. Check the plugs between the ECU and the hall switch & power stage. They are in the rear corners of the engine compartment beneath the diagonal strut braces. Clean any plugs between these components. A wiring diagram manual would be good to have at this point.

Good luck.

bagle 87 745t

Thanks for the tip, I didn't know there were some other connectors there, the
ones I was aware of were the really difficult to deal with ones tucked up
tight underneath the dash in the passenger cell. I will hunt about for the
ones in the engine bay. As for a wiring diagram, I'm essentially using the
diagram for the EZ118K system it seems about the closest to what I've got
- I have an odd ball EZ100K model - so if you know of where I can get a copy
of the wiring diagram for one of those, I'd be keen to hear it (it stumped the
local volvo dealership).


cheers
Tony