Inside a fuel injector tester (with schematic)

Описание: More information from Andy Brown. The reason the coil is driven with two voltages is not for reducing power dissipation. It's apparently called Peak and Hold, and is to give the injector enough power to open quickly, but then reduces the current so that the lower magnetic field collapses quickly when turned off, so the injector closes faster.

A bit more probing does show 6.8V across the zener, but the voltage drop across the regulator is high and gets even higher under load. With no load the regulator was putting out 12V, but with a 10 ohm resistor as a load it dropped to 8V as shown on the oscilloscope.

The oscilloscope I used is a very basic single-channel DSO150 unit that I chose to use purely for it's very simple controls.

In use a fuel injector is fed a pressurised supply of fuel and gates it into the cylinder as a fine mist electrically. Common failures are blocked nozzles resulting in low fuel volume or a coarse spray pattern. The injectors can often be cleaned and fitted with new inlet filters.

This unit causes them to fire so that you can either hear them click, or observe the quality of the fuel spray. The full size garage units have the injectors in a chamber so they can be observed operating, and the really posh units monitor the fuel throughput too.

I do plan on taking the injector apart too, but it is both welded and crimped shut, so that's going to be a dremel job.


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