Fuel Injector Tester build

#12

Joined Nov 30, 2010
18,223
I question D2
12V 1W zener
It doesn't need to be a zener at all.

I question D1
Is 1 amp really enough to run a fuel injector?
 

cmartinez

Joined Jan 17, 2007
7,749
... I question D1
Is 1 amp really enough to run a fuel injector?
It depends on its RMS current drain. Some injectors I've measured peak at 4A but then go down to less than 0.5A for the rest of their cycle, which is more than 12 times as long as the peak.
 
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#12

Joined Nov 30, 2010
18,223
Perhaps because that chip does not have any features about time limiting per button press or a pulses per second generator. Most of the circuitry in post #1 would still need to be attached to the chip in post #5
 

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shortbus

Joined Sep 30, 2009
9,441
Couldn't that be done easier with a 555 and lm393? Like Bill Marsden's pwm driver? Thing about the injector drivers is they have good mosfet gate drivers built in. And their made for the job.
 

#12

Joined Nov 30, 2010
18,223
Couldn't that be done easier with a 555 and lm393? Like Bill Marsden's pwm driver? Thing about the injector drivers is they have good mosfet gate drivers built in. And their made for the job.
You will have to consult with TS about discarding his example of a proven circuit that has the features he wants and converting to your design.
 

PackratKing

Joined Jul 13, 2008
847
Only in the last few years, have I been involved with fuel-injection, and the related computer systems supporting the functions...
Right off the bat, I attached leads, w/ alligators to a Rat-shack 8-AA Battery holder, just for a method of proving that a given injector works properly, and a means of holding one open to back-flush an injector with MEK, for a sludge / varnish cutter, which works wonders and restores proper spray profile...

The many sensors and controls, which have sway over how long an injector stays open while the engine runs, can be cobbled into an old "Sun " diagnostic machine, or your o'scope... one at a time...
What boggles here, is an injector, must be dispensing less than a drop of fuel at a pulse, since there are only 90,840 [give or take] drops in a gallon... considering how many charges are ignited per cylinder @ - 2000 rpm, and who maintains a constant 2K RPM anyway...
Which leads me to believe that there is a definite upper limit to the MPG of a small 4 cylinder engine...
 

shortbus

Joined Sep 30, 2009
9,441
The fuel injectors are rated in pounds per hour not drops.:) And your right there is a MPG limit but it hasn't been reached yet. Remember the stoichmetric ratio in an ICE is ~14.7 but so far they shoot for that but aren't getting it reliably.
 

JoeJester

Joined Apr 26, 2005
4,390
I take the TS is using this circuit as a basic test jig.

As a test jig, it will perform a functional test on the injector, whether it opens and closes properly, and allow the mechanic to see if there is flow or not flow .... and possibly the cleaning that was mentioned.

Improvements to the circuit would require a definitive listing of what one requires of their injector tester.
 

Thread Starter

Dr.killjoy

Joined Apr 28, 2013
1,196
Sorry the late posting but I am looking to test the injectors while they are still on the vehicle ..The purpose is to find a bad injector or find or other related issues ..
I was going to build the original project just to have a working model and then will work on building the LM393 and compare the two..

Couldn't that be done easier with a 555 and lm393? Like Bill Marsden's pwm driver? Thing about the injector drivers is they have good mosfet gate drivers built in. And their made for the job.
I will hve to check out the circuit and my require some help on the schematic..




Thanks for you help
Jay Sr
 

shortbus

Joined Sep 30, 2009
9,441
Can't imagine how you will do that with the injector installed in the vehicle? With an injector installed all that is visible is the wiring connector, how will you tell what is going on with the spray nozzle that is down inside the intake manifold? When testing an injector, they usually spray into a beaker or other container and measure the amount and spray pattern for a given time. To check in the engine if it is even working you just need to unplug and see if that cylinder stops firing no 'tester' needed.
 

Thread Starter

Dr.killjoy

Joined Apr 28, 2013
1,196
Can't imagine how you will do that with the injector installed in the vehicle? With an injector installed all that is visible is the wiring connector, how will you tell what is going on with the spray nozzle that is down inside the intake manifold? When testing an injector, they usually spray into a beaker or other container and measure the amount and spray pattern for a given time. To check in the engine if it is even working you just need to unplug and see if that cylinder stops firing no 'tester' needed.
Sorry I don't have all the really nice scanner right now but I am working with what I got so far .. If the build works out and I like the circuit I might have a couple pcb built and might do a give or something but not sure yet...


Oh sorry here is the full article
http://hackaweek.com/hacks/?p=1156
 

shortbus

Joined Sep 30, 2009
9,441
Still don't see how that would really tell you anything about the injector. A mechanics stethoscope on the injector body with the engine idling would do the same thing.
 

Brownout

Joined Jan 10, 2012
2,390
I would think either a 1S or 5S pulse would be way too long to test an injector for proper operation. Such a long duration would mask issues with turn on/turn off fuctionality.

To do it properly, you would need a tester that operated the injector in more realistic conditions. And for that, the circuit may not perform correctly.
 

debe

Joined Sep 21, 2010
1,295
Apart from pulling an injector out to see the spray pattern, ive just unplugged each injector plug until the faulty one is found. Usualy find that the faulty one is blocked. Some ive recovered by removing the internal filter basket & reverse flush.
 

#12

Joined Nov 30, 2010
18,223
I'm with shortbus on this one. Really sounds like you're making a big job out of this when it's really as simple as pulling a spark plug wire on a 1965 mustang. Unplug wire, no difference, bingo. That's the bad one.

The last one I did (2008 Chevy Van) was ratted out by the on-board computer. Look ma! No brains required!
 

Thread Starter

Dr.killjoy

Joined Apr 28, 2013
1,196
I would think either a 1S or 5S pulse would be way too long to test an injector for proper operation. Such a long duration would mask issues with turn on/turn off fuctionality.

To do it properly, you would need a tester that operated the injector in more realistic conditions. And for that, the circuit may not perform correctly.
Ok then what would you suggest..
 
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