Science fair project help, with used car parts


I have a question that I hope to get some feedback on about injectors etc… I have no real experience with fuel injectors and need some feed back before I go off half cocked and waste my time. What I want to do is a science fair demonstration. Where I demonstrate the performance or operation of a fuel injector visually. This will demonstrate how the car’s computer by controlling the signal to the injector it can meter the precise amount of fuel needed and any given speed by controlling the on time. What I want to do is get a cheap used injector and fuel pump a from a junk yard. Mount the injector on top, facing down and inside a enclosed transparent box, in air, 8 inches above a fuel reservoir. In the bottom of the box there will be a fuel pump submerged in my “fuel”. A colored liquid that is non flammable for safety reasons. I’ll use a 12dcv plug in power supply, for power to the fuel pump and injector. I will connect the fuel pump to the injector with copper tubing and with a simple button switch control the on time and showing the injector spraying fuel. Will this work as you see it? Any suggestions on safe fuel, is dyed water ok? What distance does the injector spray? Thank you for your help.


You might want to include the pressure regulator portion of the injection system so as to get an accurate spray pattern. This might also require a return line to the supply. If you know that the injectors get the full system volts (approx 14 volts dc) to operate them, then it would be a simple matter to set up your pushbutton to operate the injector on demand. Unless a repair manual or other source could confirm this voltage for you, the only way I would know to measure the voltage due to the short time duration is with an oscilloscope. Otherwise, just go for it and run the injector on 14 volts; it might be ok.

I don’t know how aggressive a gasoline injector is but probably not as aggressive as a diesel injector. Diesel injection pressure is high enough to penetrate flesh. The only cure is to amputate to get rid of the diesel fuel.

Sorry, can’t answer your other questions.


I think I understand what you want to do. But you’re going to need at least 45 psi of fuel pressure or more you’ll want the fuel pressure regulator, and you’ll have to set up the return line also. So you’re looking at a lot of work. Also water may give you problems, most pumps and injector don’t like water. Oh don’t forget the tool to remove the tubing from the injector.

If what you want to show is just the fine spray inside the box, I’d just use the spray end off a spray bottle, (you can dress it up to look like an injector) I would use a pressurized bottle for a fuel tank (I’d be willing to bet it’ll take less than 5 psi to make a nice fine mist) and a solenoid with a small battery. Once set up you just press the button and you should get a nice spray.

Hope it helps.

My opinions are subject to change with new facts.


You can start searching for a injector tester for “CIS injectors”. This little rig most likely will be found packaged up with the address of an automotive museum on it. These testers were non-electrical and you could see the spray pattern of the injector and there was a gague that let you see how much pressure it took to set them off.These rigs were indespensible for fuel injection testing in the late 70’s through the 80’s.A new injector tester had to cost 500.00 back in 1980 (I never had to pay for one, just estimating)


I think your idea is an excellent one. And yes, colored water will work perfectly. Just be sure your power supply can provide the current necessary to run the pump. You don;t need to use an automotive pump.

If you choose to, you could even expand on your project to show why fuel injection provides a superior burn over a carburator. You could use a venturi made from hard plastic tubing and a plastic “fuel bowl” with a tube from the bottom of the bowl to an orafice in the venturi. You can show how the veturi will pull the colored water from the bowl, but disperse it into much larger droplets than the fuel injection. You could then explain the relationship between surface area per volume of the fuel and how it affects combustion of the fuel. With a clear plastic injector setup and a clear plastic faux carburator setup the differenec in dispersion should be obvious.


Colored water is not going to work, it has too much surface tension. I would recommend kerosene. Kerosene is combustible but not flammable. The difference is that gasoline gives off vapors at room temperature which can be ignited by any spark, even static electricity from someone’s clothing. Kerosene must be heated to over 700°F before it gives off vapors that can be ignited. It is safe at room temperature.


Interesting point about the surface tension, but if it doesn’t work I’d be more inclined to suggest adding a simple surfactant. Perhaps the stuff sold at the WalMart to prevent the rinsewater from spotting would do the trick.

I perssonally don’t think vaporizing kerosene in a science fair setting is a great idea unless the goal is to deminstrate combustability. The most powerfull law in all the universe is Murphy’s Law.


A fuel injector will not vaporize the kerosene, it will atomize it, not the same thing. But your idea of using a dishwasher rinse aid sounds good to me, I didn’t think about that one.