1991 Mercury XR6 0C100861-0C239552

This motor has no spark.
Mercury book tests dcv at black/yellow wires on both switch boxes with wires connected.
Should have 100-240vdc @ 400 rpm etc. I have 0 vdc.

So then book says disconnect black/yellow from both switch boxes and retest.
(1) If now normal, it is a wiring, ignition switch, kill switch issue. I removed kill switch, still 0.
(2) If still bad, test stator. Stator resistance all normal. Trigger resistance all normal.
Have to try disconnecting wiring harness to remove key switch after the flood goes away and also disconnect 2 yellow wires to reg and retest.
In the mean time, I'll continue.

INNER: With kill wires connected, stator output on blue wire <20vdc (should be 100-240vdc).
With kill wires disconnected, >200 vdc blue and kill wire connection.

OUTER: With kill wires connected, stator output on blue/white wire <20vdc (should be 100-240vdc).
With kill wires disconnected, < 20 vdc blue and kill wire connection.

So the above test points to stator. But....

Book also mentions about moving wires from one component to another to see if problem follow. If it follows its the stator, if it doesn't follow, it's the switch box.

So took blue and red from inner box and swapped with blue/white and red/white on outer box.
Problem stayed on inner box. As in, I still get the 20vdc on the "now" blue/white on inner box with kill wire connected, but good when kill wire disconnected. And same on outer.

Anyone one with more years of experience than I wanna jump on this one? I'm only in 10 years in the business since graduating school.

Let me also add, I disconnected the shift switch and the timing advance modules also. And even with the above testing, I've still not had any spark on either of the 6 coils. Had key switch in run position and using my remote start switch while testing to ensure spark would happen if things were working.

I'm so far stuck on IT'S THE SWITCHBOX and NOT THE STATOR since the problem stayed on outer switch box...as in the blue wire voltage didn't go up when it's kill wire was disconnected like the inner box did.

..."the book says disconnect black/yellow from both switch boxes and retest. "

So. did you try this?

Jeff

The blk/yel wires send the the 300VDC from rectifier in switchbox to ground thus killing engine. The voltage will be at the switchbox terminals and should have no reading on the wires at all. You are using a DVA adapter to test correct? Usually if you have no fire on ALL with a Merc its usually a stator as rare to have all 3 coils fail in trigger or both packs fail, something usually fires. Moving wires to other switchbox and still no spark say low speed side out .Does it have the big piggyback water cooler rectifier?

faztbullet: I'm not following your statement;
The blk/yel wires send the the 300VDC from rectifier in switchbox to ground thus killing engine.
The voltage will be at the switchbox terminals and should have no reading on the wires at all.

If everything was normal, with key off, you should get 200vdc on blue AND on bl/yl would
show 0 because it's being grounded by key switch. I believe that's what you mean?
Yes it has the water cooled rect but it checks out fine! Resist and cranking voltage within 1.5v of each yellow

Last test I did yesterday pointed to switch box, using the CDI guide.
With blue and bl/yl connected, key off, swb gives me 20vdc on blue (bad). 0vdc on bl/yl (normal)
Removing blue on swb and testing stator again now gives the normal 200+ vdc on blue.
And the CDI guide says that is the switch box!
Which makes sense now.
My first post I may have wrote it incorrectly because I couldn't remember if key was on or off so just disregard it.

Normal readings:
If testing bl/yl on swb with key off, 0 vdc (normal if key switch is off and kill switch in run) because it's being grounded. Blue should still show 200vdc.
With key in run, lots of vdc (normal) on bl/yl since nothing's telling it to ground out, but blue is still 20vdc.

The blue stator wire supplying volts to swb will also always have the same volts to bl/yl as long as key is on and kill switch not engaged. Normal

So to rule the stator out, key on, kill switch in normal, remove blue and test wire, get 200vdc.

That will not make the other box not fire...it should have spark from testing you have posted. Have you tested bias circuit?

Yes bias is both around 15k ohms. Disconnected rect, same results.
If you look at CDI Tshooting where the stator DVA readings are, you see this note.
(*) This reading can be used to determine if a stator or pack has a problem.
For instance, if you have no spark on any cylinder and the stator's DVA reading is low -
disconnect the stator wires and recheck the DVA output.
If the reading stays low - the stator is bad. If the reading is now within spec - the pack is bad.
(NOTE) If both Blue wires read low, check the cranking RPM. It must be more than 250 RPM
And this is what we're seeing here pointing to swb. I'll list again my steps.

Key off - kill switch normal position
1. Inner box - bl/yl - 0 vdc (normal since key is grounding system).
2. Blue- 20 vdc (bad) should be 180 vdc+
3. Outer box - same results.

Key On - kill switch normal position
1. Inner box - bl/yl - lots of vdc
2. Blue - 20 vdc
3. Outer box - same results

Now, and according to CDI guide, disconnect blue from swb's. If vdc now normal, it's the swb (yes) If it remained low, it's the stator (no).

Just finished doing all the test again, same result.
Key on, outer box, blue, 20vdc, bl/yl 200+ vdc.
Remove blue wire, get 200+ vdc = switchbox.
Also, no volts on outer box wires to coils and 0vdc on all 6 coils.

Inner box, blue, 200+ vdc.

So if you remove stator wire and now vet correct voltage, stator is good.

I understand what you meant about it shouldn't be preventing inner swb from firing its 3 coils but it is in fact not!

Only other thing I've found is that every coil (blue ones) have resistance of .4 all the way to 14 ohms from + to -,
(spec is .02 - .04), but good from + to plug end, all .900ish ohms.
So they all seem bad.

6 coils cant go bad at once...That is 2 separate 3 cylinder ignition systems commoned by bias circuit. If that box is bad it will prevent the other from firing as the trigger uses the opposite box to complete circuit.

IDT all 6 coils are bad, but #2 had the higest ohms of 5 but I believe I read somewhere that a bad coil
can burn up a switchbox as well.
There's some confusion with coil specs too. Mercury book for these models state primary of .02 - .04 ohms.
CDI book says .02 - 1 ohm.

In 35 years I could put all the bad coils I found on a Merc in a 2 gallon bucket.

Lol yes I've not found but maybe 1 in my time.

Anyway, switchbox was the culprit as I determined! Replaced both, engine good!

See post #10.....