R.E.D Posted April 4, 2017 Share Posted April 4, 2017 I just finished replacing the electronic e7 with the mech e7.the new engine has the tach sensor on the right side of engine bell housing. Previous engine had it below the starter.I plugged the new sensorry to the harness but tach won't work.Sometimes i see 3.9 to 4 volts out plug bit sometimes there is no voltage.Does the tach run thru the ecm first?Now that there is no ecm maybe is not getting any signal?Odometer works.Can you guys help? Quote Link to comment https://www.bigmacktrucks.com/topic/49394-tachometer-questions/ Share on other sites More sharing options...
R.E.D Posted April 5, 2017 Author Share Posted April 5, 2017 I figured out that the now unused ecm cuts power to the 4.9 volt lead to the back of the tach after 6 seconds.any way to bypass this ? Quote Link to comment https://www.bigmacktrucks.com/topic/49394-tachometer-questions/#findComment-366484 Share on other sites More sharing options...
R.E.D Posted April 6, 2017 Author Share Posted April 6, 2017 Is there a wiring diagram for the tach available here at Bmt?I want to remove the ecm from the truck since it's just taking space but I will be loosing speedometer and tach Quote Link to comment https://www.bigmacktrucks.com/topic/49394-tachometer-questions/#findComment-366592 Share on other sites More sharing options...
Titanbuilder Posted May 13, 2020 Share Posted May 13, 2020 I'm in the same boat. Did you figure it out? Quote Link to comment https://www.bigmacktrucks.com/topic/49394-tachometer-questions/#findComment-451063 Share on other sites More sharing options...
R.E.D Posted May 14, 2020 Author Share Posted May 14, 2020 No ..I bought an aftermarket tach that ran off the pulse from the alternator..it fit in place of the old one...the aftermarket tach has a adjustment knob in order to match it up to real engine rpm. Quote Link to comment https://www.bigmacktrucks.com/topic/49394-tachometer-questions/#findComment-451126 Share on other sites More sharing options...
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