MS-II connected to a rocker switch rather than igition key?

[WELDER]

Hello everyone. Feels good to finally be here.

My MS-II and some other goodies are enroute, via Canada Post

The megamanual is amazing, and I feel quite confident about the upcoming installation...although we all feel great about it, until something goes wrong.

My first forum question may come across as silly and is in regards to this image http://www.DIYAutoTune.com/images/tech/ ... iagram.jpg

I won't be running a relay, but in terms of getting power to my MS-II, is it the same idea as in the picture? One negative to battery, one positive to battery and a second positive to the ignition?

If it is, can I run the second positive wire that is supposed to get power from the ignition switch (key) directly to the positive terminal on the battery, with a rocker switch interrupting the wire...which would be in the cab?

Sorry for the long-winded question.

To say it simply, is there anyway to not mess with wiring the MS to the ignition, and controlling power to the MS with a rocker switch?

Thanks in advance.

[Bernard Fife]

Welder,

You can do this. The main consideration for the wiring is that you should never allow the injectors to be powered when MegaSquirt isn't. This is because when MegaSquirt is not powered, the injectors might still be 'on', and the engine will flood with fuel, be *very* hard to start and possibly hyrdolock one or more cylinders.

The diagram captures it for power, you have a ground, and full-time power, and switched power (normally the ignition, but you can use a rocker switch).

Lance.

[WELDER]

Thank you Lance!

I figured it was wired to the ignition simply for convenience and possibly a fail safe or two, like the one you mentioned.

I'm sure I'll have a few more questions throughout my build, I'm very happy that msefi.com exists

As I'm new here, and not familiar with the forum etiquette, would someone care telling me whether or not we delete posts like this (ones that are answered quickly) to keep the board uncluttered or leave them for reference for others?

Thanks again.

[Matt Cramer]

Normally, they are left as a reference for others; posts may be deleted after they've been around for a long time with no further responses.

[WELDER]

Makes sense.

Thanks.

[WELDER]

So, getting closer to install time.

I searched and got very close to getting a straight answer, but didn't quite nail it down.

On my MS-2 wiring harness, I see the one that says 12VDC, that one will be my switched positive right? Which ground do I use to ground the MS itself? Just one of the black wires, or all the black wires that are left over once my sensors are grounded?

[Mike_Robert]

It would be acceptable to connect all of your leftover grounds to the same good grounding point. An important point is that the sensors must be grounded at the MS. If you're using the DIY harness I think there's a wire labeled sensor return or similar. It sounds like you've done this already.

-Mike

[Matt Cramer]

On our 6 wire harness, we recommend using one wire as a sensor return and grounding the remaining 5 to the battery negative terminal or the engine block.