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Random rpm dropout triggering off coil -
Posted: Sun Aug 28, 2011 2:15 pm
by jon volk
I am getting my rpm signal off the negative side of my ignition coil. Wired to the optoin+ to the negative side of the coil and optoin- to the 12v side of the coil. Gets a stable rpm signal but it will randomly drop out, usually at higher rpm and it also seems to do it more often wih longer run time. Any suggestions on cause?
Re: Random rpm dropout triggering off coil -
Posted: Sun Aug 28, 2011 3:13 pm
by dontz125
Take a look at this post - it apparently gives a gloriously clean square-wave signal.
http://www.microsquirt.com/viewtopic.ph ... 86#p151772
Re: Random rpm dropout triggering off coil -
Posted: Sun Aug 28, 2011 4:04 pm
by jon volk
Thanks, Ill give that a whirl and see how it goes.
Re: Random rpm dropout triggering off coil -
Posted: Mon Aug 29, 2011 9:37 am
by jon volk
No dice. It would not get ANY rpm signal with the diode and resistor setup in that thread.
Heres a bit more info. Its a 63 Ford Thunderbird using a gm tbi unit for fuel only. The ignition system is the oe distributor with a pertronix module replacing the points. The coil is stock. I had it wired per my original post and it would start right up but rpm signal would drop out over say 2500rpm. As the car warmed up, the rpm signal would drop out more and more to the point it wouldnt stay running for more than a second or two. Tried the diode in line with the coil- (band toward coil) 1k resistor off the coil + combined both legs of the diode and resistor and hooked it to the opto+, opto- was grounded. This gave no rpm signal to the ms.
the other thing that has me concerned on this issue is the car started and idled fairly well for a decent amount of time, around half an hour with only an occasional reset idling or when reved. Now it will rarely fire at all (when it shows no rpm input).