Using Tach output from MSD box to trigger MS 2 ( fuel only)

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Darren
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Using Tach output from MSD box to trigger MS 2 ( fuel only)

Post by Darren »

Hi I have been fighting a hard starting problem for over a year now and I think I may have found the source to my issue, I just wanted to run it by you folks and see if anyone has any ideas.

It's Fuel only on a MS 2 V 3.0

What I think is happening ( or what it appears to be from the datalogs ) is..

Key on
Fuel pump and priming pulse happen (3.0 ms prime)
Turn key and crank engine it fires immediately then dies ( after a few more attempts at cranking it will eventually start )

What I see in the datalog is the prming pulse but then when I go to crank I don't see a tach pulse for about 2-3 Seconds( if i'm cranking and the engine doesn't actually fire),
So it looks like the motor fires on the priming pulse and uses up that little bit of fuel but because it starts to run momentarily but does not see the tach pulse right a way no more fuel is being added therefore the engine simply dies.
I currently have the MS hooked to the Tach output on a MSD Digital 6 Box. Was thinking of trying the Negative side of the coil, but have been hesitant as this starting problem does not exsist with my MS1

If anyone is interested I would be more than happy to post up a datalog of the starting attempts I'm at work right now that is why I can't attach a file right now :D

Thanks in advance
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Matt Cramer
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Joined: Sat Jul 03, 2004 11:35 am

Re: Using Tach output from MSD box to trigger MS 2 ( fuel only)

Post by Matt Cramer »

That sounds about right for what's going on. I'd make sure you have D1 and D2 jumpered, and if that doesn't work, try the VR conditioner circuit. Never try triggering off the negative terminal of the coil when running an MSD box.
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Darren
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Posts: 6
Joined: Tue May 18, 2004 7:24 pm
Location: Vancouver B.C.

Re: Using Tach output from MSD box to trigger MS 2 ( fuel only)

Post by Darren »

Hi Matt, thanks for those suggestions, one question, those fixes you have recommended to try are for VR sensor inputs set up, however I am currently configured Hall/optical/points. Should I be configured to VR settings when triggering from the Tach output on MSD?

Thanks
Darren
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Darren
MegaSquirt Newbie
Posts: 6
Joined: Tue May 18, 2004 7:24 pm
Location: Vancouver B.C.

Re: Using Tach output from MSD box to trigger MS 2 ( fuel only)

Post by Darren »

Sorry Matt one more tid bit of information on my set up, ( it's a VW aircooled) I have a pertronix II dizzy going to the MSD digital 6, I am currently running the ignition as stand alone and Fuel only on the MS3.

Thanks again for your input on this.

Darren
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Matt Cramer
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Joined: Sat Jul 03, 2004 11:35 am

Re: Using Tach output from MSD box to trigger MS 2 ( fuel only)

Post by Matt Cramer »

Usually you would use the Hall / optical input, but the VR works too and would help rule things out.
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Dariocc
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Joined: Thu Mar 20, 2008 5:02 pm
Location: Mendoza - Argentina

Re: Using Tach output from MSD box to trigger MS 2 ( fuel only)

Post by Dariocc »

Darren, have you fixed the problem?
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