DIY Pulsed Fuel Injection Tester

01-15-2011, 11:29 PM
Hi folks.
I'm an auto tech and I always appreciate a good diagnostic tool. Many of you are probably familiar with fuel injection testers. They come in a few varieties but they usually work the same. You connect it to the car battery for power and then connect it to the injector to be tested. When a button is pressed the device sends a pulsed voltage signal to the injector which simulates what a control unit would do.

When used along with a fuel pressure gauge this can give the user an idea of the volume of fuel each injector is delivering. The technique goes like this. Pressurize the fuel system, turn pump off, monitor the fuel pressure drop when the injector tester is fired, compare to other cylinder's injectors. Pretty simple and sometimes very revealing.

These devices sell for anywhere from $135 up to $400 depending on what they do. I wanted one for myself and since I like to tinker with electronics I decided to build one. This one cost me about $20 in parts from Radio Shack.
If you're at all into building things with electronics, I encourage you to visit this link on my website and build one for yourself. The parts list, schematics and a video are all there for you to use.

This tester will output an 8 millisecond pulse for a duration of 1 second. I plan on designing and building one soon with variable pulse width and duration, and with an LCD readout.
Enjoy! :cool:

02-03-2011, 02:31 AM
Nicely done

02-04-2011, 06:12 AM
Thanks. :)
I'm working on an updated circuit that has variable output duration.
Check my blog ( for details.

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