The fuel pump circuit in my MS <MSIIv3 board> is hot at crank time, w/ or w/o the engine running <RPM >= 400>. I think the circuits B+ drops as rpm approaches 0 AFTER STARTING for safety's sake; but this behavior is muted at crank time.

YMMV.

--f

So, it seems I need to connect the key-switched coil (+) from the OE harness to the switched +12v lead on MS, power up the MS in the car and see if the fuel pump circuit is active in START and RUN. If so, I can connect the optical distributor sensor power leads and a new coil leads to the fuel pump circuit. Is that right?

Frank

here's what I did. Pin 28 <yellow> is DEFINITELY hot at cranktime.

For the distributor, I have a load resistor <1 ohm> at B+ to try and make the "detector" thingie embedded in the ignition sensor see the same load/current it used to see with the coil -- since i have no idea of its bandwidth/freq response. Its still on the bench.

Dunno if it makes a difference. Yet.

--f

Your setup is different from mine - I'm using MS2-v.3 also, but I have the relay board between the ECU and the sensors. I think it complicates things for me.

Frank

Frank,
One of the most important things when wiring this up is to make sure the coil can not get power without whe processor and dizzy being powered. There is no value in trying to have them switched with the pump.
This is a simple setup and needs to remain so.

Yeah, when I was reviewing MS, I came to the same conclusion: the relay
board is a complication -- perhaps an unnecessary one.

Since the 'bishi already HAD 3? relays <the old 'vacuum computer'>
that would go unused, I didn't see a reason/need for it. Using the
existing relays held a lot of packaging advantages, and allowed me to
fully use the existing harness, and its weatherproof connectors.

Std relays are easier to troubleshoot and <spontaneously, i.e. NAPA> replace,
I think. I only had to add <pull> three add'l wires to the existing to make the whole
thing work!

If I were adapting to a car that didn't already HAVE an ECU, it would have
made things easier having the board.

My 914 had such a board; ancient bosch printed circuits which fail from
heat/moisture, with relay sockets atop. It goes in the heap, replaced
by the MS board.

So, the "relay board" really serves TWO purposes;

- Makes installation of new features much
easier than re-soldering the DB37 <messy> on a full harness, IN THE CAR;
- and allows higher current controls where needed <i.e. fuel pump>.

My use of the harness adapter accomplishes the first objective, without
the relay board -- and without REQUIRING it when it isn't useful or needed...
such as, when the target car already HAS a bunch of relays that are no
longer used. Or, adapting sensors, where you'd like to MINIMIZE the number of joints
to corrode and change values, like TPS and TEMP.

YMMV, as you're doing some special things. But, I thought the
distinction about 'dual function' important enough to post.

HTH.

Charlie,

The coil has its own "driver circuit" within the MS controller.

I don't think there is a way to wire it up
otherwise, on the megasquirt. Only the dizzy gets "switched",
unless you're using crank sensors.
And it doesn't really require a relay, except for convenience
<i.e. one COULD use the ignition switch B+>.

If the MS is off, the coil sees no current, correct?

And there is NO need for a switched relay "port" to intermediate this connection,
it just gets accessed using a "relay board" as an interface.

Am I missing a subtlety in
your post? I wholeheartedly agree; keeping it simple is good.

--frankb

Charlie -



That's why I wanted to wire it the first way I mentioned - key switch to coil (+) and tap that connection for "MS +12v switched" and "distributor optical sensor +12v". When the key switch is in ON or RUN position, the MS is activated, fuel pump is activated, coil is energized and distributor is ready. That's about as simple as I see it can be done. What am I missing other than the chance it might be electrically noisy?



Where on the relay board would you suggest I pull power? What do you mean by "same source"?

Frank

Right..... I should have mentioned that I'm triggering the coil (-) from the internal driver option in the MS ECU.... not using the power transistor.

Frank

The driver circuit is controlling the ground/ trigger side of the coil. This circuit is closed when no power is applied from the processor, If the coil were to receive power it will be grounded through the driver inducing a high current flow. This being why the coil should not get power when the MS is not on.
Even with external triggers as with multi coils this is important. Most of my work with MS has used either Bosch or Mitsubishi drivers, and I have had my seared fingertips even with them.