Erratic tach - D180

[SammyQ2]

Right now, the engine is running rough, since I am in the initial programming stages. But, when I run the engine to 2,000, the tach bounces between 2,000 and 1,400, faster than the engine could change.  It does this when I select either left or right tach operation.  It seems to work fine an lower RPMs.

I am using both right and left tach inputs to the D180.  For RPM right, I have a 30K ohm resistor between the mag switch and EMS pin 33.  (Slick 4301)

For RPM left, I have tied to a fuel injector +12V line.  In normal operation +12V is always supplied to the injector.  To pulse the injector, the +12V grounds through the EC3 ECU.  I have a wire tied in, between the injector and the ECU and it connects to EMS pin 32.

Any idea how I might proceed to eliminate this bug?

Sam
Quickie Q-200

 

[dynonsupport]

The EMS only reads one tach at a time. If the one it's reading goes to zero, then it switches to the other one. If that one is zero, it hops until one reads something. There's no way to know which one it's on if both are active.

Your best solution is to remove one source (pull the wire) and figure out which source is causing the bouncing.

Not sure we've ever had someone hook to a fuel injector, but I also don't see why it wouldn't work.

The only reason for the twin tach input is so you can do a mag check and not lose your RPM readout. Your injector pulse never goes away, so you don't really need a connection to the mag.

I do have to ask for my own curiosity: What kind of engine setup are you running that has both a magneto and an electronic fuel injector?

 

[SammyQ2]

So, selecting LEFT or RIGHT isn't really selecting which input is being used?  I assumed that it did.

I am installing a Real World Soultions EC3.  I am keeping one mag, for the time being, but will propably switch to all electronic within a year.  For the rest of the story go to www.samhoskins.blogspot.com

 

[dynonsupport]

Where are you selecting LEFT and RIGHT? I don't think there's any option for this in the EMS.

 

[SammyQ2]

Look on page 6-8 of the D180 installation manual. I interpreted that as a selection, as well as a position. I guess it is not.

 

[dynonsupport]

The only thing that selects is if the tach is on the left side of the MAP or the right.