Source
r/MechanicAdvice•
subtlefarts

Finding the motor's RPMs without a tach

Solved

I'm going to be doing a carb rebuild this weekend on an 84 Ranger. The truck doesn't have a tach, but I'll be needing to read the RPMs to properly adjust the carb once its rebuilt. Is there a way of getting this information without having to install a tach? There is no obd/obd2 port either.

Posted Feb 5, 2016, 4:26 PM UTC

25
mattwrotethis•

You can buy a handheld tach/dwell meter (if you can find one) or a multimeter that can read engine RPM. A cheap tach from the parts store could be hooked up with alligator clips temporarily if you don't want to permanently install one. It'd be red to positive, black to ground, green to negative side of the coil, and white to positive if you needed illumination in most cases (always verify with the instructions included).

5
skiier862•

Not sure what you have access to, but my fluke multimeter has a rpm clamp that you put around a spark plug wire and it'll tell you engine rpm

2
spasticpoodle•

http://smile.amazon.com/AGPtek%C2%AE-Professional-Digital-Tachometer-Contact/dp/B004Q8L894/ref=sr_1_1?ie=UTF8&qid=1454697031&sr=8-1&keywords=photo+tachometer

1
rcrracer•

Amazon

1
larrymoencurly•

There are multimeters made for automotive use that will measure RPM, and they're available from Harbor Freight (model 95690, $36 with clamp-on inductive pick-up), electronic supplies (Jameco, MCM Electronics, Contact East) and maybe Sears.

1