How to test a fuel injector for flow problems (GM)

This vehicle has an intermittent misfire that we are trying to locate. Here we will be focusing on the injectors, making sure they do not have any flow problems (restrictions or leaks)
An external timer tool will be used to fire the injectors at exact intervals while watching fuel pressure drops on a pressure gauge.
Since we cannot get to the injector connectors directly, we will be using a main bulk connector to access the injector control wires. This same procedure can be applied to many different systems.
Engine Performance Diagnostics chapter 18 page 26
Symptoms
intermittent misfire
check engine light (P0300 fault code)
Fix
I don't remember but it wasn't the injectors :)
Tests shown
injector balance test using an external timer tool
Tools used
fuel pressure gauge/kit
electronic fuel injector tester
test light (LED or incandescent)
jumper wires
back-probing tools
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Playlist
(Chapters 17, 18 and 19) Fuel Injector Testing
Playlist
• (Chapters 17, 18 and 1...
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
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Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

[@mike-yp1uk]

Great video. Sometimes I put these videos on instead of music and as I listen I can work and still visualize that's how I know I fully understand the material. Great video.

[@ArthurJGuy]

I've never heard of this test before my car had it done today, but not only is it a great test you did a great job of explaining it.

[@MrFreddywise1]

Insightful information as always, what i like about your videos you really go into detail with what your teaching your students, an don't just show one way of how to test things, great work as always Paul cheers

[@ScannerDanner]

@Amopower Two things, first the cylinder balance test is just an RPM drop test. It will only isolate which cylinder but not the cause. It could still be spark, fuel or compression. So this test may still be necessary after verifying which cylinder has low contribution. Second, you are correct in your comment, this is a volume test. Check out my first video on a 2005 Neon with an injector problem. (that is if you can bear the poor video quality of my phone, it was my first video:)

[@PANOS9916]

Seems so logical process and yet many technicians mess it up

[@ScannerDanner]

@jdubb408 Yes, the control wire on the tool is a pulsed ground and you connect it to the injector control wire which is also a pulsed ground by the PCM. The tool substitutes the PCM in this test and fires each inj. for an exact amount of time. The pressure drops will indicate leaking or plugged injectors. Check out my 2005 Neon Injector Problem video (poor video quality,sorry) for a leaking injector using this test.

[@Amopower]

That's a pretty neat quantitative way to compare injectors. My 94Probe has EEC-IV which lets you do a cylinder balance test, and I think it does so by dropping power to each injector one at a time and checkign RPM differences. I like this way better, seems more accurate. So the idea here is that if you pulse each injector for x amount of seconds, then each of them should emit the same volume of gas, which in turn translates to a pressure drop.

[@timeless6964]

Just the video I Need!!...I Have a 91 Cavalier Z-24 Multiport 3.1, that has Completely Hidden Injectors!!...Only problem, I am Color Blind!!....But I will Do Every Pin, and take it from there!!....Thanks, I Needed This!!!

[@blackville3]

Hey Paul you are a great teacher!

[@ScannerDanner]

Thanks so much!

[@ScannerDanner]

@Amopower Some early 80s Chrysler and Mercedes Benz had power side switched injectors, but if you are connecting the tool to the injector itself and not into the harness as I did in this video, it wouldn't matter about the polarity of the tool. Always check a diagram to be sure if you are doing what I did in this video. Follow Section 3 in my book for solenoid identification using a voltmeter or wiring diagram.

[@huracan200173]

ScannerDanner you're the man, but the video end with "[Enter your name here]" made my day hahaha you rock! Your videos are awesome =)

[@ScannerDanner]

If the test light "bypass test" worked and the ECM fired the injectors. You have one of two problems. Either a bad module or a short to ground in the purple/white reference wire.

[@ScannerDanner]

it is also an ASE cert. It is the L1 Advanced Engine Performance patch

[@nickayivor8432]

Good Morning 🌄 KNOWLEDGEABLE Sir ScannerDanner Thank you very much helpful video Have a great day and take care PRODIGY Sir ScannerDanner From Nick Ayivor from London England UK 🇬🇧

[@martyisabeliever]

Noid light simply indicates power present at injector; Pulse tool allows control of injector on/off duration: Check cylinder balance by firing individual injectors at 1/2-second increments in three different ranges: 1 pulse of 500 milliseconds, 50 pulses of 10 milliseconds, 100 pulses of 5 milliseconds. Power and output lights indicate test activation. Includes wiring harness adapter and instructions.

[@ScannerDanner]

did you replace the module? The parts store test only checks the transistor function, not the RPM signal output.

[@ScannerDanner]

Sorry man, did the best I could. Hard to do this over the computer. Also once you start changing other parts, you start adding problems. If you replaced the module and now have no spark then it is not the coil. You may have disturbed the pick-up coil leads and wiring one too many times. If you now have no spark, you have either a pick-up coil or module problem or a main power or ground problem to the module.

[@mdanny445]

Great video, but i just wanted to say, would of been good to include a reminder to start the vehicle afterwards so as not to flood Engine. But still great!

[@jacobbarth1862]

I was just doing this today at work but bi directional.. Biggest pressure difference was 3 psi but mitchel/shop key said that was in spec.. slight slight random rough idle used some fuel injector cleaner and sent him on his way. If he comes back I’ll feel more comfortable attacking that sell I just couldn’t rationalize a 600$ repair on such a slight problem. Let it worsen a bit if it even does.

[@seshachary5580]

very educative thank you

[@Engineerboy100]

I would just remove the 12 nuts and remove the intake manifold, ... better yet I would NEVER buy a car designed like that OMG! smh Cool tests though and mad crazy trouble shooting skills! Best part of the video is your helpers name "Clint" that's my name too lol

[@ScannerDanner]

lol I didn't even know that was there. I guess I have to edit that don't I. thanks for the heads up

[@ScannerDanner]

Power to the injectors is supplied by a fuse on this model. When you checked for power how did you do it? Test light? Voltmeter? Or by the injectors not spraying fuel you are assuming you have no power? Let me know, I can help further, but be patient with my reply

[@ScannerDanner]

ok cool, sorry to panic there in my response. I was concerned about the test you did. All is well, change the ignition module and let me know what happens. Oh, very important question though. You said you did have spark right? Because if you do not there is another test we must do first before module replacement.

[@fd9431]

Pretty slick.

[@juanyboo12345]

THANK YOU SR FOR UR TIME AND GRAT VIDS GOD BLESS YOU

[@ScannerDanner]

I wouldn't use it for an ignition coil. There is too much amperage from a coil. You could pulse other low current solenoids though.

[@train4905]

Superb sir.steve from uk

[@TRcustomengineering]

Another Great video. Thanks very much.

[@Element_lifestyle]

Can u please give information how it will look with a bad injector . Performing this test! Thanks

[@ScannerDanner]

I never told you to replace the coil. I said the ignition module or there was a problem with the reference wire.. Also we were dealing with a GOOD SPARK, NO INJECTOR PULSE problem. Now you tell me you have a spark problem?

[@wilsontran1943]

Thanks Can you show me how I can test wire misfire 4. Toyota runner v6 4 liter please

[@webslinger724]

I am currently going through this right now on a 3.6 impala

[@chevyboss97]

Hey paul do you know if the 97 3.1's have that fuel pump test connectors? I know my car pretty well but i havent seen a connector like that. Thanks. Great videos.

[@sivucit]

hi, i assume we can use this tool to bench test ignition coil by connecting positivewire ignition poistive and control wire of this tool to ignition negative. Please advise. I also assume this tool can be used for any pulsed ground circuit, like EVAP solenoid, etc.

[@CPUTests]

An injector is not much than a coil, so you DON'T need to see what polarity the test tool have. You can put it reverse and the injector will pulverize equal way and same quantity of fuel. So you don't need to see what is the control and the ground. You are only energizing the coil inside the injector so as long as you don't exceed voltage of the injector, you can put it any way, I mean control on 1st pin and GND on 2nd, and vice-versa is THE SAME THING.

[@ScannerDanner]

@00G000 Thank you!

[@Amopower]

Are all/most injectors pulsed ground, or does one have to research their car first before getting this tool? I also looked for this tool in the meantime, and cannot find it, but I think it's new replacement is the 3398.

[@amilvilleda]

Good job

[@ScannerDanner]

Wrong connector, the one you are looking for has a purple/white, white, black/red, and a tan/black wire on it.

[@ScannerDanner]

Ok so you do have power. Is this a V-6? Do you have spark? If you do, do this test. Turn the key on, connect a test light to battery positive and touch on/off the purple/white wire coming out of the distributor connector. The injectors should fire every time you do this. Tell me the result of the test

[@CameronDC-Grimes]

What are the ways to test injectors without metered tools or scopes or scan tools? Like some simple trick like swapping coils. Or how most of the time I'm never getting a injector code. I used two jumper wires with alligator clips with a 9V battery to test the injectors being stuck or not by seeing if they click, then use the wires + battery to clean em with carb spray after tapping the side to unstick the electromagnetic solenoid Valve/switch to open/close the flow of fuel. Are there other teicks SD knows so everyone can do more tests. Think of it like your stuck with your friends, intermittent Crank No Start + stall on turns with a keg 😂 Broke down on side of road, no tools, no phone

[@ScannerDanner]

The only other non meter injector tests I've ever used was to use a long screwdriver as a stethoscope to listen for clicking 🙂🍻

[@ScannerDanner]

First of all I never told you to run a jumper from battery positive to that wire. I said to use a test light. And I certainly didn't say to leave it there. If this is what you have done you may have cooked the engine computer. However, you still may be ok. What this test told you is you need an ignition module. I know you have spark, but trust me you still need a module. It is the module's responsibility to send the ECM an RPM signal on that purple/white wire. It simply is not.

[@CPUTests]

I'm sure that some tools have the control on one side and other tools have the control on other side (because it doesen't matter in case of injectors. They are only a coil) and will work equal way with control inverted or not.

[@ScannerDanner]

That would be true if I was testing the injectors directly. What you're failing to realize is I was using the system voltage to power the injectors (NOT the tool) so I needed to ground the control wires with the tool only. What would have happened if I used the wrong side of the tool? I would have been supplying direct battery voltage into the control side of the injector, so the injector would not have pulsed AND this I could potentially cook the PCM driver!

[@armandonika]

+ScannerDanner hey Paul, im wondering how can you cook the driver?? (That driver should be off right)

[@little739]

So, you are saying since the car is not running, the pcm is not pulsing the injector; how can you potentially cook the pcm driver.Great question. But, If Paul Danner says it, we have to believe him.

[@johnny0454]

@@little739 ....by supplying voltage backwards into the ground side of the driver circuit. It wouldn't matter if it's on or not, voltage on a computer circuit where there is only supposed to be ground is not a good thing. It might be ok, it might not, better to not take the chance and find out.

[@arctican7483]

GOLD!

[@tbz02]

thank you! :)

[@tbz02]

what is that little patch on your sleeve below the ase one?

[@Engineerboy100]

Fuel pressure regulator ;) Mimics bad injector because they don't always get the pressure they need but sometimes they do. Very trick sometimes this one.

[@juanjolivares3291]

How is pulse tool different from the way noid lights work besides the different settings?

[@ScannerDanner]

watch my very first video on a 2005 neon with an injector problem. it is a poor quality video but still has great content.

[@abimariavargas7086]

Will 3 lbs smaller injectors cause issues or can ecu compensate

[@ScannerDanner]

Absolutely will cause issues!

[@ScannerDanner]

no, totally different amperage and on-time

[@pantelis241]

What about GDI engines ? Does this test apply to GDI engines or not ?

[@ScannerDanner]

No

[@brandonwebb2100]

How do you use scales and set triggers on scan tools without knowing Voltages

[@ScannerDanner]

Curious as to why you'd ask this question here. I don't believe I used a scope or scanner on this one. Also, are you referring to scan data parameters or are you talking about a lab scope? Thanks!

[@brandonwebb2100]

ScannerDanner the one u and Eric did when he said u need to know how to set up a trigger is the big take away on using a scanner I’m just trying to learn I love learning about cars

[@brandonwebb2100]

I’ve worked on cars I just have never used a scanner and wanted to learn how

[@chethanrajraj533]

My car was the problem it's only can take little trottel of un plugged map sensor, with connect its not running misfire too

[@cr112784]

Would this car happen to have the _fuel injector_ *spider* poppets

[@ScannerDanner]

no sir, that was the GM Vortec 4.3 and 5.7 engines only that had those

[@ateola]

Can clogged injectors cause a P2272 o2 sensor signal mulfunction?

[@jrdeel6474]

my 94s10 is running good but about 30miles later in traffic it die sometimes back fire I have changed just about everything help

[@bradjohnson5748]

Jr Deel Spider assembly...fpr

[@salvadorparada3284]

cool

[@onecleangrill6644]

how can i bring my car to you i believe you are in pa me ct

[@ScannerDanner]

@frosty9595 Yes

[@EgoShredder]

Vee-hickle :D

[@danielwarren6845]

clifton559 Why are you shouting, your comment isn't even true. In the event of a severe misfire the computer driver may shut off intentionally meaning that if you disconnect the injector it will make no change to the engine yet the injector is not at fault.