5ktq electrical problems update (not fixed)

[Bernard Littau]

[snip]
> My issue though is that ok with all of the charging system good I
> shouldn't ever go below 13v which would cure it, but shouldn't the
> ignition work fine well below 13v? Even if cleaning all the contacts get
> the charging voltage up to 14v it will fix my immediate problem, but I
> will still have weak ignition and loose power. I don't have the 2nd volume
> of the Bentley which is electrical stuff, so I don't have any wiring
> diagrams. I do get full battery voltage @ the coil.
>

The ECU and ignition should run fine well below 12V.

I have seen Hall Effect sensors get fuzzy with low voltage (that is, crummy
ones work better at higher voltage), so you might check the flywheel hall
sensor and the distributor hall sensor -- start with the wires and
connections, of course.

If you have a scope, monitor the output of the hall sensors.  You should be
able to rig the car to charge and not charge on the fly while you are in the
garage, so you can see what the waveforms and system behavior are at 13+ and
at 12 volts.

You might also want to check a known good source of these waveforms.  When
my distributor hall sensor went bad, I checked it with the scope, and then
checked the new replacement -- huge difference.  The ECU can function on a
very crummy signal.

Also, check if you are throwing any codes.

Best,

Bernard Littau
Woodinville, WA
'88 5ktq