MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

93-95 GM 3.4 OHV tach signal strength?
Posted by: limey222
Date: September 10, 2015 05:10AM

can anyone tell me what is the correct signal strength for the tach signal coming out of a standard PCM for this engine?
I assume it can be measured on a volt meter set to AC. Mine seems too low for even a Dakota Digital black box to amplify high enough to activate a VDO tach.


Scott68B
Scott Costanzo
Columbus, Ohio
(548 posts)

Registered:
10/25/2007 11:30AM

Main British Car:
1968 MGB GM 5.3 LS4 V8

authors avatar
Re: 93-95 GM 3.4 OHV tach signal strength?
Posted by: Scott68B
Date: September 10, 2015 06:53AM

I believe it is a 5 volt square wave.


Charles
Charles Long
McDonald, TN
(177 posts)

Registered:
09/15/2013 08:54AM

Main British Car:
1966 MGB V6 1994 Camaro 3.4L 60V6

authors avatar
Re: 93-95 GM 3.4 OHV tach signal strength?
Posted by: Charles
Date: September 10, 2015 09:22PM

I have VDO gauges, so when I tried to use the output from the coil pack I could only get 0.4 Volts. The guys at VDO said 4.0 V was min. I now use one of the phases from the alternator. Vdo has the setup to use the alternator. I have 3.4l V6 GM.


limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Re: 93-95 GM 3.4 OHV tach signal strength?
Posted by: limey222
Date: September 11, 2015 04:56AM

my PCM tach feed in the BMC harness is only putting out 0.35 volts so i will have to go with the aleternator signal route.


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