Jips

was looking for the tach filter on my 1990 3gen v6.
Read somewhere that is must be behind the distributor, but can't find it there...
Somebody who knows where to find it?

grtz, D

 

There isn't any...

RBob.

 

In that case, it could be a problem....
on the line to the tach, is get a 5v pulse, about 4ms long.
But the tach does not reponds......
When I put a 6v sinus on it, it do responds....

I get rid of the distributor, and put a DIS on it...
Is there a difference in signal between a distributor and a DIS?

 

Yes, the DIS tach output is 0 - 5 V pulses.

The distributor tach output is 0 - 12 volt pulses along with some inductive kickback (it comes off the coil negative).

Easiest solution is to use a NPN transistor and two resistors as a level-shifter. Shifting the pulses from 0-5V to 0-12V. I posted a schematic of this someplace on this V6 board.

RBob.

 

I've never had a problem running a GM tach off a DIS module (when it was originally used with a dizzy), nor with my Nissan tach (though it did have a different issue that had to do with duty cycle at high RPM...), using the GM DIS.

There should have been a tach filter on the car, and leaving it in place does seem to cause issues when using DIS. Typically the filter is located on the driver side of the firewall, sometimes it's part of the harness, closer to the fender...

 

I think I go for the transistor...
I believe I have some here, somewhere.....
Thanks for the tip Rbob!!

@Six_Shooter: If it causes issues, it would not a bad idea to remove it....
There is nothing on the firewall... can you tell me how the one in the harness looks like?

grtz, D

 

Here is a post where I described the level shifter:

https://www.thirdgen.org/forums/v6/5...ml#post4419622

There is some other good info in that thread for running a DIS setup.

RBob.