I'm a mechanic in Canada, the video and the comments is leaving me with impression this tool is used just to see if an injector works and frankly if that's all the information you need just start the engine and listen to the injectors with a stethoscope. This tool becomes indispensable for an injector balance test where we take manual control the fuel pump running it up to max pressure then feeding a pulse train to a single injector and noting the fuel pressure at the end. We do this once with a short chain of long pulses and again with a long chain of short pulses and repeat for each injector. Any outlier has a different flow rate than it's companions and is suspect. For valid results the pulse chain has to be the same total on time for every test so build it or buy it you need a proper tool.

Several years ago I built a DIY engine controller called Microsquirt. Their documentation talks of low impedance Peak-and-Hold injectors that use 4A to open quickly and 1A to hold them open. I believe the lower current was both to reduce heat and, as already stated, let them close quicker.

Another interesting thing about injectors is that you can electrically test for a mechanically seized one by looking for the pintle hump or the lack thereof, as the pintle moves between the open and closed positions it changes the magnetic circuit length which changes the inductance of the coil and you can see it as a little hump in the coil current as it ramps up and back down. There are many videos about it by people such as ScannerDanner.

That drive scheme is called peak and hold and helps with time response while also limiting power dissipation. For lab testing NI makes hardware that lets you set multiple parameters to drive injectors.

I'm now working on a ecu project and could understand why they made this circuit that way. They used this kind of short pulse of higher voltage prior to the main pulse to be compatible and set a higher current on low resistance injectors found on older injection systems. Such injectors have resistance lower than 1ohm and will damage the mosfet and the injector itself if turned on for a long time. Its not a common case and the newer injectors (after 80s) have resistance about 14 ohms and they are drived without these pulses or series resistors as in these older systems. Its a smart solution but the limited current node may be monitored by the microcontroller to turn the mosfet off if a short circuit was dectected. On modern ecus all outputs are current limited and have self diagnostics.

That looks like a very typical injector curve, high power spike is to pop the injector open with the pressure on the inlet.

Have had over 30 years of fuel injection work. Yes some injectors are very low resistance and require current controlled switching, others just a reduced holding voltage once pulled in. The injector duty cycle which can be from very small to even almost 100% duty has a large range of power dissipation. Normally high duty factor only applies to full engine power and high RPM regions also thus high heat conditions. The 100% point is never really allowed, and to be avoided as fuel delivery is no longer controllable accurately by On time so by design the sizing of injector normally would be chosen to remain way below 100%, experience say under 60%. At 100% On, and near time duty regions, flow rate becomes non linear to duty cycle too, as mechanical travel time and dynamic flow factors create a dead time effect, offsetting flow by a small time factor so effective zero flow starts at some small On time factor, linear with On time, and duty cycle grows as RPM demands faster pulse rates, but as duty cycle forces time On reaches closer to 100% that time offset also causes deviation of flow from linearity. That upsets fuel to air ratio and engine performance and emissions. Of course as volatile fuel contains very light fractions, vaourising at low temperatures, and fuel goes through ithe injector, t is highly important that coil dissipation NEVER allows heat released to vapourise lighter fractions of the fuel to form micro bubbles that would seriously affect fuel delivery accuracy, thus also engine fuel to air ratio thus also performance and engine emissions. Now, yes the fuel flow cools the injector, but as the injector also experiences much external heat of the engine, especially on non cross flow engine designs with inlet and exhaust on same side of the engine, interleaving inlet and exhaust, that heat local to injector can be very high. So extra coil dissipation is quite potentially important, tipping to internal vaporisation issues. Much effort is made to keep injector coil dissipation low. Low resistance and inductance, allow initial high current faster mechanical action, but if left at full power on would be detrimental heat wise, so initial high voltage or current peak and current control or switched lower voltage becomes desirable. For this tester the lower voltage step has two possible reasons, firstly the dissipation is critical as likely it is often used with dry injector no fuel flow and thus no cooling, so the prevent coil overheating and possible damage to injector they limit power in On state. Second reason, it is desirable to verify that the injector can hold in when exposed to reduced supply once pulled in. Thus testing for adequate "Hold In" capability. Initial pulling voltage of injectors is often above 7v to 8v, so testing with limited 5v supply would prevent many, not all, injectors even switching on (pulling in). Thus they have this double supply level design to cover the wide range of objectives. Sadly to realistically test injectors this mechanical activity falls far short of injector evaluation, beyond ensuring it is not in a mechanically stuck state. Nothing verifies the accurate fuel delivery or spray pattern of the injector, or leaky nozzle, all of which are far more common problems than physically stuck state. I would regard this tester of minimal value, beyond very rudimentary injector test for dies it click when energised.

This comment section has brought the gearheads and ele-chickens together. I love seeing such a wide variety of people commingle together on common ground.

That's so clever!! I've never considered using a zener diode to change the output of a regulator, much less modifying it on the fly with a transistor! Fascinating.

Back in the late 90s I built an injector tester rig. I only work on BMWS so that makes standardization easier. It’s setup to do 4 at once. I used a fuel rail off a 4 cylinder and have 4 graduated cylinders to measure output over time. A buddy of mine built the controller for it. It uses a pwm controller to vary the output and a timer integrated. It’s an old washing machine timer that controls the time it runs and the pwm signal goes to all 4 simultaneously. It has proper transistors controlling each injector and I have the factory fuel pressure regulator on the fuel rail and have a small resivour to keep the cleaner in. And of course a fuel pump. I have been using this contraption almost 25 years. I am able to measure the fuel output and observe the spray patterns. I don’t know of anything else that could be done to test injectors. I helped him fix something of his and a couple of weeks later he called me with the idea. We started talking and I got the parts together for my end and he got the electronics ready. We built it one weekend. Started on Saturday and Sunday about 2pm we were testing it. By 3:30 it was installed and we were enjoying a few beers.

Looking at the specs for a 78M05, I see a few interesting points that probably explains the maximum 8V output you were seeing. 1) The minimum dropout voltage is 2V at 500ma. So minimum input of 7V for 5V out. 2) The maximum output current is 730ma at a headroom of 5V. If the car is running (which it won't be) the battery voltage is nominally 14.4V. If the car is not running (which it will be) and if the battery is in good shape, it might be 13.2V. 3) The 6.8V zener + 5V regulator is nominally 12V, BUT only if the input voltage is 12+5 = 17V. Which it isn't. 4) With 13.2V in, the no-load output is 11.0V. With 12V in, it is likely to be 0V out, since the regulator will have dropped out. 5) With 800ma load at 25C you need about 5.2V headroom. So 13.2V-5V = 8.2V, about exactly what you are seeing. Over all, the 78M05 was a very poor choice for this regulator. A simple NPN pass transistor would have been a lot better choice.

Pinball machines have been using that drive scheme for decades. They provide full current for the flip, and (at least for older models) there was a travel limit switch that injected a current control resistor for holding. Same concept: Fast initial response, but don't burn it up during the hold.

Modern injector drivers will pulse the injector with higher voltage to quickly open the ejector, then let the coil current drop to a lower level and then pulse it to keep this lower level for the rest of the duration. This also makes closing the injector quicker with lower stored energy.

I like the scope. I have an appreciation of any tool that lets me see what is going on inside.

a tubeless valve stem fits over the end of the injector (with its O ring removed) and the other end is a decent fit on the straw of a spray can wrapped in tape. It's a pretty common trick to make an injector tester/cleaner to use with an aerosol can of cleaner spray.

😂so now the trick is to incorporate the fuel injector in to the SodaStream.

That clunky reset mechanism makes me wonder if they just had issues with something triggering the mode switch or MC reset line while in operation, and rather than work out how or why they just disabled the onboard reset with that capacitor and went with the dumbest brute-force reset instead.

Yeah, the peak-and-hold injectors almost bit me too. About 20-some years ago, when I was a real gearhead into drag- and street-racing, I wanted to "upgrade" from the factory 19-lb/hr injectors to something higher. I remember asking around about some 'new' style of injectors I'd seen, and found that they needed a peak-and-hold circuit, which would necessitate modifying my PCM with new transistors and other circuitry. In my mind, this was kind of a "one-way street," as far as the PCM, and I was still paying my way through community college, so I held off. I'm pretty glad I did, because IIRC I blew the transmission a short time later. :p

The peak and hold was normally used with low-Z injectors. One very early application that used it was the older throttle body injection systems from the 80's. Those had very low impedance coils with big, heavy pintles inside since they basically emulated the jets on a carburetor. My memory was that there were current sense resistors in at least one of the ECUs I had worked on that told it when to "fold back", but that one could also handle bank and batch saturated fire injectors as well since it was made for multiple truck models. Those old injectors did need it since the impedance was only a few ohms, and the heavy pintle had quite a lot of inertia. It was one reason I stopped using TBI back in the day and went to SFI, as the injectors could not fuel a motor at high RPMs due to them having to fire alternately with each ignition coil firing. To actually get it to even work at 6k RPM I had to run them at around 80 PSI, which was much higher than the 12 PSI they were designed for. I was always afraid either the O-rings or the regulator diaphragm would fail and burn the car to the ground. I think here the peak and hold is probably included to actually accommodate more types of injectors and safely power them. (Edit: Dissipation is also a potential concern as some types of injectors use the fuel for cooling as well. When running them dry it could be possible to overheat them. Same with a lot of older fuel pumps that literally had open-frame DC motors inside submerged in fuel that required the fuel filter for removing debris from brush and comm. wear.) Typical non-DFI motors that use conventional high-Z injectors usually run them in saturated mode. There are mosfets that just act as switches and simply complete the circuit for a desired duty cycle when they are commanded to fire. The newer DFI injectors are likely different in that they have to open under much higher pressures and have to fire over very short spans of time. With an SFI system, you have up to two full crank revolutions to complete an injector firing and I used to set up the calibrations in PCMs open them fairly early so the fuel could have time to vaporize in cold weather, but even warm I still allowed for about one full revolution in advance so it had time to fire. With DFI, it has to be done within the intake cycle, which is much shorter.

anyone else notice clive put the ground to right terminal and tap left terminal of the injector when showing just the injector = 0 clicks. then when showing us the the tester he connects the tester the opposite way around? and clicking happens?!! great video Clive, great little tester to see who is watching carefully!! haha, even the thumbnail didn't give it away by the looks of comments I seen

I work for a heritage railway as a volunteer and our fuel injector tester is a single fuel pump bolted down on a beach with a presser gauge and you connect the fuel injector to the pump tester and pull the handle down and if it working OK it should be a find spray at the right pressure with NO leaks. Some hope. I'm talking about diesel engine that are over 60 years old

Another facet of peak and hold injector drive is it helps minimise fuel heating. Thanks for your videos, they're always interesting to watch.

Very interesting this as you have got some very knowledgeable people commenting here too as well as your in depth test and schematic Injector Clive

I built one of these years ago with a 555 timer and transitor. It had a lot more control over the pulse width and just ran for as long as you held down the button.

Fantastic to see the comments from those knowledgeable on fuel injection. Well done all.

He gets me every time with the pictures of the PCB.s ... 🤣

clive your videos (and car wizard’s) made me comfortable enough to attempt diagnosis of a parasitic draw on my old german bucket o bolts. thanks for making electricity a bit less “mystery magic” and more fun

@Big Clive a running engine is not running at 12V, unless your Alternator is dead, a Running engine is at 13.8v to 14.8v to maintain a charge in the battery. the Alternator puts out more power, than 12V

A few companies manufacture what they call "hose tail adapters" for people who wish to use an alternate, newer style injector on an engine that was designed to use injectors that have a hose barb on them. They are not cheap, except when compared to having someone manufacture a custom fuel rail.

Your above mentioned voltages may be different, if you loop in the actual injector coil instead of a resistor. Because you mentioned the posh versions with metering funktion: No injector test is valid without fuel metering and comparing to specs. That's, where the countdown impulse mode comes into play. In this case here, without any luxury provided, you just use a separate metering device. You get similar devices for simple bench testing of common rail diesel injectors too, but the fuel delivery is a bit more challenging, since there is no easy electric pump solution. And then care has to be taken with the high pressures involved. The metering device has to be sufficiently strong glass, the jets are shooting right through plastic. But Diesel injectors don't open with the solenoid or piezo alone, they need fuel pressure applied as a preload at the valve needle.

This is hardly related to this video, however your pronunciation of Zener as Zee-ner has led me to question my assumption that this should be Zen-ner. I did some research and found the obituary of Dr. Clarence Zener, the inventor of the Zener diode. Here it clearly states that the pronunciation of his surname is Zee-ner. Therefore, I feel that is proof enough that I was wrong and you are right in your pronunciation, as the useful little diode was named after the man himself. Thank you, Clive!

Fuel injectors are designed operate with fuel as a lubricant. Running them dry causes wear just like in the races of a solvent cleaned, ball/roller bearing, spun fast (for fun) by an air compressor.

That is called the peak & hold method of controlling an in injector with varying voltages: higher voltage initial start to pull open the pintle and then a lower voltage after that to hold it open, but creating less heat dissipation. Another way is opening the injector with a short solid pulse and then holding it open with pulse modulation at the same voltage. Saves all that voltage regulator and zener etc stuff. Third (very wierd) way its been done is on some 1980s Bosch ECUs in Beemers and Porsche 911/944 is that all injectors are wired in parallel and are controlled by 2 (!) transistors. Upon the initial opening pulse for the injectors transistor#1 gives a ground path for the injectors from 12v to slam the pintle open, but right after that Transistor#1 (to ground) is turned off and transistor#2 is turned on, now supplying 12v positive to the normally switched ground of the injectors, thus basically having the injectors supplied with 12v on both pins. The magnetic field in the injector coil now cannot collapse and thus the injector stays open for the rest of the intended pulse duration till the moment it is intended to close, and here transistor#2 stops conducting, and the inductive kickback of the now collapsing magnetic field in the injector coils gets discharged through a big zener, the injector closes and everything is set for the next pulse. Took me quite a while to reverse engineer that, I uploaded a video on YT some years ago where I explain one of these oldschool early Bosch Porsche ECUs Cheers from Germany

Fascinating, and cool to see one of those little scopes used (I have one somewhere) but I think for fueling I'll stick to my twin SUs!

I can't speak to cars, but I know in my pinball machine it does a similar (but totally different) trick. A pinball flipper is capable of dozens if not hundreds of watts. That trigger can only be for a few fractions of a second. If you hold the flipper down and hold power to it, within seconds it will try to let the magic smoke out. To combat this, mine in particular has 2 coils in parallel. One high power kick, and one holding coil. When the flipper reaches end of stroke, it breaks the connection to the high power solenoid so that only the holding coil remains. They're doing the same-ish here for the injector, just in voltage instead of hardware. Makes sense for coil longevity.

Nice to see a Holtek driver in there, I've just finished a project which used several. Tricky blighters to hand solder.

If you look for 'peak-hold' injectors, you may see why the voltage spikes then drops to a steady state. It allows the coil to be driven and then held without pulling more current than necessary. This is probably implemented to this device so that its compatible with all/most injector types.

Modern gasoline direct injection systems run on 60v to boost and 12v hold. I'm sure there are plenty of other configurations as well but I know GM does that.

I knew he'd have to use his best Chinesium scope for the task! No way in hell would he offend people by using one of those "snobby" Agilent scopes! :-)

On cars, the injectors are fused to B+ so it has what ever voltage is on the system. The negative is going to the ECM where it is switched by a mosfet. Nice the injector usually are running fuel through them in normal operation, I doubt any heat dissipation is done. I would have to connect my scope between the signal wire and ground and get the volt drop to see if there are any current limiting on the circuit

I have one that is very similar, but without the reset button. You can generate enough enough pressure with a plastic syringe to check the spray pattern. Just find one that fits snugly into the end of the injector. It's cheap, but it works okay for me. Thanks for the video Clive! 👋

It makes sense to drive a relay or solenoid actuator this way. It will also make sense to use such mode in an injector cleaning station in which there's a mode of just pumping the cleaning fluid through injectors for some time, so in a such way coils wouldn't overheat. In stations pulsing injectors in a regular manner continues the cleaning process and then test of injectors' volumetric capacity for different pulses duration/frequency follows, but using a lower holding current for short pulsing injector - no sense whatsoever.

just to add after the smarter people than me answered already: while not so much in gasoline engines, Diesel injectors still use this method actively as the pressures holding the nozzle shut are much higher, the coils require lower impedance and usually higher voltage (depends on manufacturer's driver ciruit as bosch, delphi and denso all differ in such details) to start the injection event and subsequent hold thanks to the fact that most if not all makers stopped using less than 3 events per cycle so at usually 600 µs for the whole duration and 18ms between injections (at 750rpm) they have to be kinda fast

You have low impedance and high impedance injectors Because you have bank and batch and individually fired injectors depending on the system .

Thank you! I have not exercised the part of dyslexia I actually enjoy in quite a while! Reading upside down and backwards as if it were normal...damn, do love doing that, then noticing... 😎

The ECM will also vary the on time to regulate the amount of fuel injected. That is referred to as pulse width.

automated whoofler ?

I'm more of a carbs guy myself (who mentioned my waistline?!? 😅) but as time has gone on, I've had to start to learn the more primitive EFI systems. A little tester like this would be useful for a DIY'er, you could check operation, measure delivery and get a reasonable idea on spray pattern. Not the same as a pro job but better than not doing anything, especially if you're chasing a fault. One thing that I've also seen in passing, in certain factory/dealer manuals they show oscilloscope waveforms for various components including injectors. The earlyman diagnostic computers had oscilloscopes built in so you could test throttle position sensors, idle air control valves, stepper motors, MAF sensors etc etc and get your various voltage and resistance readings from them to compare against your book figures. Some companies such as Austin Rover had standalone test units for each system, they were called FastCheck. You plug it in and it told you how much your British Leyland product was inevitably broken 😅 (I know, I've had them, loved them and still own some). Niche vehicle diagnostic stuff is really interesting kit, often cheap to buy too.

Injectors are typically switched directly to ground.

I have the exact same tester it has come in handy with checking injector

Great to see BigClive using an scope..

A lot of manufactures of the newer style "direct injection" will vary the power to the injectors and then switch the negative for whatever pwm is needed for fuel management. The new petro cars of today processors are getting up to 1GHz speeds but are typically limited going faster due to temperature and environmental stability for automotive specs, so individually controlling power and pwm to each injector can be intensive for v6 and v8 engines...

Clive, put that injector in a vice then file it lengthwise to expose, by layer, the inner workings of it. I’ve done it, it doesn’t take long, and it blew my mind. I’m stunned the things actually work but they do. It would make for a great video.

Nice review video

Electronic fuel injection systems on automobiles vary the pulse width to the injectors depending on throttle position, temp., air flow ( in some cases manifold vacuum ) etc. There is usually a load resistor in series with with each injector. A timing pulse from the Control module give the injector a start time and cut off time and depending on the aforementioned cues the control module receives from it's various sensors and it will vary the pulse width within the start and stop time allotted to each injector. Some early injection systems would fire all or pairs of the injectors at the same time. At least Bosch systems are like that. Interesting little tester but most mechanics just disconnect the injectors one at a time with the engine running to determine a faulty one, or read the codes.

The LM1949 is designed for minimizing heat dissipation, as well as being able to drive both low impedance and high impedance injectors, the lm1949 will drive the injector at full power until a preset current is reached (or a specified r/c time) and then drop into current limiting mode which I think is 1/4 of the setpoint current. This does a few things other than minimizing heat.. for one, a high impedance injector will never reach that current, so it gets driven as if the LM1949 wasn't there, secondly, it provides fast opening and closing times since the current through a low impedance injector will be much lower and you don't need to wait as long for the magnetic field to decay. The LM1949 is typically used with a BJT and something like a 0.1ohm shunt resistor I discovered it when I took my Holley commander 950 injector controller box apart.. not a cheap chip at about $5, but it works very well

I’m guessing that the higher voltage required is probably due to the intended use of the vehicle battery as a power supply. Excellent investigation as usual.

@Big Clive - the Automotive Industry - has the C.A.N -Buss bi-voltage controller aspect to it .

Most mechanically propelled vehicles diesel or petrol, whilst running will have a return voltage from the alternator to the battery of 13.5v, you may need to consider this.

In your opinion are these injector testers worth purchasing? I love your videos and I've learned quite a bit from them and I look forward to seeing the latest ones.

Speeduino is an open source ecu. You can check theboard and atmega based code.

Usually the ecu for the vehicle will vary the pwm going to the injectors, also called injector timing to give more or less fuel based on how much air is entering the engine and how much the throttle/butterfly valve is opened. With what you were saying about the voltage across the injector it sees the full battery and alternator voltage so 12-14v. If you have any questions id be happy to answer them. Thamks for the info

"12V" vehicle batteries is a misnomer based on rounding the 2.1V per lead acid cell down to 2V. In fact, a 6 cell lead acid battery is 12.7V at full charge and at less than 50% charge at 12V, which is about as low as it can go without damage. The system voltage needs to be in the 14-15V range when the engine is running in order to charge the battery (current flows from higher voltage to lower) but parts required for the engine to run (like the injectors) need to operate at a bit less than the battery's normal 12.6V during starting. Taking all of this into account I am not surprised that the injector needs slightly above 12V to work.

nothing like coming out of a dissociative state to a big clive video.

Great as always

Did you check for the initial spike on the single shot ? Maybe it's more to protect the circuit when pulsing, specially in mode 4

There is two fuel injector styles. .peak and hold or saturation. On average peak and hold use 4 amp opening current then clamped by pwm to around 1 amp at 14v. Saturation injector has a resistance of between 12 and 16 ohms. There latency or dead time Is slower but overall life is greater.

these are pretty handy for use in pressure drop testing for automotive diagnostics, just measure how much the pressure drops in the fuel rail for each injector and you can find the bad boy

In datasheet the HT46R47 is called as 8-bit OTP Battery Charger Controller

I've assembled an Arduino based EFI intended for driving two low impedance injectors in parallel. It doesn't feature peak and hold because I think Throttle Body Injection doesn't need it, since the injectors don't spray directly into the combustion chambers (but you could add it if you know Arduino programming).

I'm sure you could make a jank fluid inlet with a length of hose and a hose clamp. I would answer your question the the pulse deal but I see plenty others have already done it.

In the engine ECU in cars have a mosfet for every injector. I have brought many ecus back from the dead by replacing the injector drivers which are just mosfit transistors.

That'd be a peak an hold type. There's 2 ish types of injectors. High and low impedance injectors. High spike at the beginning helps open the injector fast, then lower voltage only holds it open.

PRECISE VOLUME OVER TIME. This is used to COMPARE to other injectors. This is to MAKE SURE the volume of fuel passed, is the SAME on all injectors. This test MUST be coupled with a fuel line PRESSURE sensor. THIS NOT FOR TESTING A FUEL INJECTOR THAT HAS BEEN REMOVED! THIS IS FOR TESTING FUEL FLOW VOLUME!

Remember, just because something doesn't make sense or seems wrong to you (not anyone in particular), doesn't mean it wasn't done that way for reasons you didn't think about. Happens all the time.

I built one like 20 years ago still works today if you want to see the schematic let me know

The scope image answer: Thats a Petrol injector for starters and that is a good pattern on the scope. as you said the spike to pull the coil hard against the fuel rail pressure and open it, the lower voltage after is the pulse width so how much fuel is injected, longer for cold engines short for hot but also longer for accelerating and short for idle. The injector will cut off very briefly on deceleration but not all of the time as an engine does like a little fuel over its valves. Great Video and that looks like a good tool for the toolbox, but may not work on diesels? Thanks Clive

Great for building your own petrol based testing units. But it's the diesel ones which go wrong more and the high pressure is a bit sketchy to work with 🙂

Hey Clive, did you build a kit or buy the oscilloscope finished? I have one just like it, I built as a kit. I never would have done it if it weren't for you and your videos. You taught me that soldering isn't that hard and nothing to be afraid of.

Perfect while submerging the injector in brake cleaner

Clive you can use silicone tube in the inlet of the injector to fit it on a butane refill can to make a cool flame puffer

I'm weirded out that it wasn't using 14.4V as reference, an "alternated" voltage, but 13.8 seems like a bare minimum with bad alternator almost broke scenario they may shoot for

Why did I start laughing when you pulled it out of the box and I saw the Chinese instructions. Lol

Ok will get my scope out and have a look. I know they guys that use the machines talk about micro pulses also? I have put off due to being busy and a covid to go back to this customer and look at the old Bosch injection machine which is pure TTL and analogue. The faults I have fixed before have always been psu or input damage so now it is more interesting to look at output.

Also remember for better efficiency,you want cold fuel (cold air is denser, therefore contains more oxygen), so injector heat from the solenoid is a consideration ,i wouldn't be surprised if car controllers are doing the same, high volts injector pulse to low volts holding pulse.

I'm sure we want to dremel the fuel injector open :blushing smiley face:

I used an audio amplifier and a tone generator program on my computer. set it to square wave and adjust the volume until your injectors start pulsing. Rig them up to squirt in graduated cylinders and you can do a balance/flow test

Like others have said peak and hold injector setup, I was cheap I needed one made with an Arduino works ok.

As a retired design of Engine Controllers, when driving an injector with a coil resistance in that area we drive it at battery voltage with a MOSFET for a few 1/10 of a second, no idea why they would drop the level back to some lower voltage. Now for direct injection types we pulse them initially with a series of 80V pulses and then lower it to battery but those injectors have a could resistance of 2-3 ohms.

oh the obsolete internal combustion technology. Fascinating.

Now that would make an interesting Whoofler...

It's nice to see they've added the reset button, although it would be nicer just to be able to change modes without the need to reset at all. I have an older model, that didn't include a reset button, it requires the input supply to be disconnected and reconnected every time you want to change the mode, so a P.I.T.A. So, after using it a few times and getting annoyed, I simply added a momentary N/O push button, and a 5 pin mini relay, both mounted nicely inside the unit. I connected the N/C 30/87a terminals of the relay to make/break the positive input supply line, and the push button triggers the relay to N/O momentarily to reset. I occasionally find my unit loses output pulse, although the green 'working' LED flashes as it should and everything appears to be working, there's no output pulse to the injector. I've visually inspected the board thoroughly, and wiggled the output wires while doing a continuity check and no breaks in wires etc that I can tell. Not sure if it's a problem with a component on the board, or something dicky/intermittent with the output cables...hopefully your explanation of the circuit will help me track down the issue, but we all know how much fun intermittent problems can be🤣🤣👍🇦🇺

It seems there is still some EMI that is getting picked up on the audio circuits of the camera. Not surprising since its fast switching into that inductive load. I wonder if they had problems with the uProcessor locking up?

WOOOOO New BigClive!

Thunderf00t used one of these (and the box of tricks) in some of the testing for his Sodium fuel project testing, interesting to see inside of it :)

I’ve seen ones with little enclosures for some sort of fluid (or did they legit use fuel?) Either way you would mount them in there and not only test them electrically, but also look into Spray Patterns or even get fancy sensors on the case etc.

So, most gasoline (petrol) fuel injectors use between 3.3 and 5 volts. They use a "driver" from within the PCM (Powertrain Control Module). Some of those testers are a bit sketchy. For reference, I have been a Mechanic for 35+ years now. Feel free to ask me any info you need on this subject. Have a great day, Sir! o7

Clive, did you get the idea for this from watching Thunderfoot? 🤔 It actually makes sense that it would take closer to 13v. That's more in line with the running voltage of an engine. It's easy to forget that while the battery is 12v the engine runs off the alternator with tends to more like 14v.

A Full Charge "12v" lead battery puts out 12.6 to 13 volts so this thing may see 12 volt as a "Dead" Battery and won't test. Car computers can see same and cause other issues, set error codes, etc. even tho engine may start with battery at 12V or less.

Interestingly, the engine management in a typical gasoline/petrol port injection vehicle would not function this way. On a high impedance injector (like the one you have) it would just get fed straight “12V” (more like 14V) on the power side and be ground-side switched with the full ground. So, nothing special. Some cars use “peak and hold” injectors that are lower resistance (usually 2-4ohm). For those, they still get fed full battery voltage, but the ground is where the magic happens. They get the full ground to open them, but then the ground voltage gets elevated to maybe 4-6V by the injector driver, current limiting the injector. The injector is closed only by the spring in the injector and the fuel rail pressure acting against it, not electronically. Peak and hold injectors are not common on “modern” port fuel injection systems and were mainly used in early PFI systems or throttle body injection systems or “central” fuel injection systems (where they used 1 or 2 big fuel injectors to supply the entire engine). However, peak and hold injectors have started to make a return in modern direct injection systems because they need the extra power to open against thousands of psi of pressure in gas systems or tens of thousands in diesel systems (sometimes paired with higher voltage). This tester is likely designed to work with all types of injectors, the peak and hold function that it seems to do by default is only necessary for low impedance injectors. What wasn’t pictured in the waveform you showed (since it was just hooked to a resistor, not a coil) is the inductive spike that would happen when the injector is turned off. Typically I’d see between 50-100V spikes from the injectors turning off.