Tach failure on 502MPI

[502fast]

My tach has stopped working. I connected another tach and it doesn't work either, the 12v source is okay but I'm not getting a pulse signal from the motor. Anybody know where that wire comes from on my Mercruiser engine? I've always had Merc outboards, this is a new animal.<br /><br />Tks in advance

 

[skeffer]

Re: Tach failure on 502MPI

On most engines it is from the negitive post on the coil. I am not sure on yours as I am not familar with the 502mpi.

 

[rodbolt]

Re: Tach failure on 502MPI

hello<br /> with no other identifying information, most MPI engines send a 5v digital tach signal generated by the computer. a lot of mercruisers also have a standard tach feed from the coil. some tachs are not compatable with 5volt signals.time tro get the manual and trace the gray wire back to the ECU or ECM or whatever they are going to call it today <br /> good luck and keep posting

 

[Cool It]

Re: Tach failure on 502MPI

Can a jumpy tach have anything to do with a bad connection at coil or can there be other reasons<br /><br />Thanks<br />Cool It

 

[rodbolt]

Re: Tach failure on 502MPI

coolit<br /> start a new post.<br /> but yes depending on the engine model it could.<br />good luck and keep posting