How to test used fuel injectors?

**wmorrison65** · 05-08-2015

I have a set of used injectors on the way, to replace one bad injector in my engine. Is there any way I can test the used ones, so I don't end up disassembling/reassembling the fuel rail multiple times?

I'd already checked resistance on my existing six, and all were similar, even the bad one, so I don't think that test will necessarily tell me which new ones are OK.

Can I test with a battery? How many volts should open them? I've seen people use a 1.5v AA cell but that didn't seem to work for these.

**J57ltr** · 05-08-2015

You would need at least a 12v battery, you can get it to click with a fresh 9v. I would backflush them with a solvent.

Jeff

**wmorrison65** · 05-08-2015

Took a chance, put in one, worked great. Doesn't take that long to get the fuel rail off/on now that I know how.

But, thanks for the advice. I had previously tried a 9v and it didn't work, but it was only putting out 7-8 volts per my multimeter. Maybe two 6v lantern batteries in series would do it.

**J57ltr** · 05-08-2015

It would for sure, or a 12VDC wall wart.

**ADrugDealer** · 05-10-2015

Or just plug them into the car? It takes like 30 seconds to get the rail off, injectors are not meant to just be given constant voltage, they are meant for PWM from the PCM... Just put them in the car

**J57ltr** · 05-10-2015

Unless they are low impedance (they are not) they will be fine.

Jeff

**coolone** · 05-10-2015

Originally Posted by ADecker

Or just plug them into the car? It takes like 30 seconds to get the rail off, injectors are not meant to just be given constant voltage, they are meant for PWM from the PCM... Just put them in the car

^^^this^^^

I was going to mention to make sure when checking them to only give voltage momentarily. Prolonged voltage could cause major problems ; )

There is a nice write up on rebuilding injectors on here too... Iirc it covers testing too.

**J57ltr** · 05-10-2015

Good lord you people. I have rebuilt injectors for more than 15 years. I have an injector test stand that i can backflow (which requires the injector to be opened for about 10 seconds), I can check the pattern and even check the balance and ultrasonic clean them. Do you guys have such a unit? Quit passing around trash information like you know what's going on.

edit: that "rebuild" only covers replacement of the basket and O rings, it doesn't test them at all.

Jeff

**ADrugDealer** · 05-10-2015

Cool

**ADrugDealer** · 05-10-2015

I really don't want to get into this argument, so let's just drop it here. From your perspective sure its fine, from the electrical engineering perspective it could be damaging. Usually things designed for PWM do not like to be ran static for long periods of time. Hence why things like transistors are current rated vs intermittence and a completely (usually much lower) number for static.

**J57ltr** · 05-10-2015

Ok, when you get your degrees in electronic engineering let me know. I have had mine since before you were born so you are talking out the side of your mouth. This is simply a ohms law question of how much power is drawn. NO ONE is going to test a fuel injector hook it up and walk away some people still have common sense. But then again that has been a problem for the past while.

Jeff

**ADrugDealer** · 05-10-2015

Which is exactly what I was saying. Maybe I wasn't clear, hook it up. Don't leave it hooked up.

Simply ohms law? where the hell did you get your degree from? Last I checked ohms law was not the only thing that governed a coils behavior under load... I didn't say "DONT DO IT IT WILL BLOWZ UPZ RITE AWAYSZZZ" I said, plug them into where they are meant to be because it takes 30 seconds.

**spazzz** · 05-10-2015

Does adding seafoam or any other hypothetical injector cleaner to your fuel, actually 'clean' them?
or does it just clean your wallet of $

**J57ltr** · 05-10-2015

When you hook it up it only becomes a simple ohms law equation. You don't take into account coil inrush or inductance, because it doesn't matter in the example we are talking about. It gets more complicate when you have to take into a count reactance but that's not the situation here. Don't try to over complicate things. Any coil that is powered continuously has no reactance and since the current is not changing the inductance doesn't matter either. Because it's static. When you drive a coil in a PWM mode THEN it comes into play, when you release power on the coil from the driving device (be it mosfet, transistor or simple contact) the coils field collapses and induces a voltage that is a ratio of the number of turns in the coil and material in the coil and usually generates several hundred volts. (Don't believe me, take a regular relay connect the coil to 12v while holding the terminals and release one lead and you will get a shock). This is way more complicated than you are trying to make this.

as far as seafoam, never used the stuff I always just remove them and clean them.

Jeff

**Booba5185** · 05-10-2015

Could heat be a factor they aren't bring up? Normally the injector has fuel running through it, maybe it's the same principle as the fuel pump? COuld it be the coil would overheat and break the connection at some point? Just sayin', not arguing or anything.

**coolone** · 05-10-2015

Originally Posted by J57ltr

Ok, when you get your degrees in electronic engineering let me know. I have had mine since before you were born so you are talking out the side of your mouth. This is simply a ohms law question of how much power is drawn. NO ONE is going to test a fuel injector hook it up and walk away some people still have common sense. But then again that has been a problem for the past while.

Jeff

And you were the one to post about people being negative? Really?

YOU have a Degree in Electrical Engineering?

Condescending remarks like talking out of the side of your mouths is real tough on a keyboard, and quite frankly, if you don't have anything good to say, something that's helpful, maybe it's best to just keep it to yourself.

For the record, it's not something as simple as ohms law, because hooking up the injectors to an external circuit or power source that has bypassed the circuitry and built in protections on the wiring harness in the vehicle 'CAN' damage the injectors. And yes, people DO do it, saying no one does it is counterintuitive. And then you contradict yourself by saying it is a problem in the past. So to surmise, your post in nothing more than diatribe... Lastly, please refrain from making assumptions about people and person characterizations that you know little of. Because you do what you do, or did, or want to do, does not make you the end all of knowledge. People come here for useful information, some are experienced, many not... so far I've seen more of you attacking posts than anything offered as useful. If you have a bench and experience why don't you just offer the info. On how to do it RIGHT!

So what does your ohms law tell you when the OP gave the injector 9v instead of 12? Hmmmmm... Meaningless right? Lol...

OP

heres the link I mentioned...
http://www.grandprixforums.net/threa...=Fuel+injector

have a nice day : )

**J57ltr** · 05-10-2015

It will burn up for sure your talking in the 12-16 watt range so something needs to dissipate that heat. Under normal use the power is less since the duty cycle is lower.

**Booba5185** · 05-10-2015

On the plus side, I have a new word of the day:

diatribe (pluraldiatribes)

An abusive, bitter, attack, or criticism: denunciation. [quotations ▼]
A prolonged discourse.
A speech or writing which bitterly denounces something.The senator was prone to diatribes which could go on for more than an hour.

**ADrugDealer** · 05-10-2015

Jeff, you are right in all that; however, you can't possibly sit there and deny the fact that running constant 12 Volts through a coil that is meant to be pulsed with fuel rushing thought it for an extended period of time just to "test" it is a good idea. I understand your experience and understand your view point; however, I disagree and think its a terrible idea.

Why not just take 4 bolts off that any monkey could get to, pull 6 sticky lookin things out and put the new sticky lookin things back where the others came from is any easier than trying to hook 12V from a battery to an injector. Its just stupid.