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  • Power supply question
  • Premier Icon teasel
    Free Member

    Hoping one of you lovely chaps or lasses will be able to help clarify something for me.

    I want to assemble something similar to this…

    https://www.dirtbikexpress.co.uk/workshop__and__tools/motocross_tools/motocross_hand_tools/motion_pro_hv2_fuel_injector_cleaner_kit?gclid=CMKr_J3n1M4CFWUo0wodRdYDYg

    …for exactly the same job. If I use, say, something like this…

    http://uk.rs-online.com/web/p/plug-in-power-supply/6158919/

    …via a momentary push button, would that be okay to power the injector without buggering anything?

    The device I linked to is powered by a 9v battery and apparently most injectors will fire with that voltage but some need 12v to work so I was simply playing safe by opting for the higher volts.

    Happy to be advised of something better for the job but would prefer mains as opposed to battery if possible. I was going to wrap up the whole thing in a nice tidy project box, obviously.

    Premier Icon teasel
    Free Member

    Anyone…?

    TL;DR – Will a 12v mains power supply fire up a car fuel injector without problems?

    Premier Icon richmars
    Full Member

    It’s current that you need to know.
    If the cleaner works with a 9v battery I think there’s a good chance the power supply will work as well.

    Premier Icon Junkyard
    Free Member

    The main issue is finding out how much power – WATTS the cleaner requires
    For example imagine its 9 volts and 3 amps[ 27 watt]
    Your supply only does 1 amp so it will blow a fuse on the power supply or will work very poorly.
    Probably need to get that info from the manufacturers as it is not on that link

    Watts = amps x volts
    find the watts and divide by 9 to get the amps

    Bit pricey to just try though but its the power supply that will MOST likely, though not certain, go not the injector

    ALso assumes that there is an easy way of attaching it t the unit and i suspect you will need to wire battery end caps for those 9 volt
    like this?

    I would assume its very low power if a battery can power it- unless you want to run it for very long periods why do you need an external power source?

    Premier Icon richmars
    Full Member

    What Junkyard says is correct, but the cleaner runs from a 9V battery. If (and it’s a big if) they mean a PP3 type battery, a quick google say they can deliver a few 100’s of mA at 9V, so the power supply will be fine. Why not just use a battery (rechargeable)?

    Premier Icon Junkyard
    Free Member

    yes I thought the same due to the scale/size of it in a hand it must be a pretty small battery and therefore low power – I put that in an edit whilst you replied

    Premier Icon teasel
    Free Member

    Really not my field in the slightest so appreciate the help, guys.

    a quick google say they can deliver a few 100’s of mA at 9V, so the power supply will be fine.

    Was just Googling exactly that myself and then looked back at the power supply and as Junkyard writes, it might just die and not really do anything.

    Why not just use a battery (rechargeable)?

    Was my original thought before I saw the pre-fashioned thing to which I linked. I started looking at a 12v rechargeable lithium ion – that the sort of thing you mean or did you mean rechargeable 9v?

    unless you want to run it for very long periods

    The reason I went with the mains power was simply convenience of use and duration; I don’t know quite how long it’ll take me to flush four injector units as it’ll be the first time and with that in mind I thought a continuous supply might be better.

    ALso assumes that there is an easy way of attaching it t the unit and i suspect you will need to wire battery end caps for those 9 volt
    like this?

    If you mean the pre-made thing, I think it’s in the unit itself so will probably already have that type of connector as part of the wiring.

    I had an idea to just stuff it in a project box via a momentary switch and off to a proprietary connector to take the charge to the injector. Nothing real fancy, just a bit nicer than loose wires all over the shop, if you get my drift – just one in, one out with a protective sheath.

    Premier Icon teasel
    Free Member

    How would I find more info on the injector or would I be better off contacting the sellers of that weird box?

    I got my original idea from watching this redneck…

    [video]https://www.youtube.com/watch?v=rUUgR94drxg[/video]

    Premier Icon raymeridians
    Free Member

    Googling suggests that in normal operation fuel injectors are pushed with a fairly hefty current (c. 4A) for a brief (few ms) pulse.

    So I’d be tempted to put a capacitor across that power supply (or battery) to give the extra heft. Some barely remembered A-level physics equations make me think that 1,000uF should be enough. I’d also chuck in a back EMF protection diode (don’t know if there’s much inductance in an injector but it doesn’t hurt).

    Premier Icon Junkyard
    Free Member

    Its certainly doable but you will require more info from the manufacturer re power which will be low

    those standard Duracell batteries are 700ma so it really cannot be much power – ie that charger above can deliver more power than that battery has so I would be pretty surprised if it does not work but it is impossible to be certain.

    IF it were me
    E-mail manufacturers and get some info on the power it uses they must know this and then work from there
    You could buy it and measure yourself and then do it if they are crap at helping.

    What you plan to do is doable if you supply enough amps at 9 v to power it – until we know that requirement we can only guess at what you need

    you can also get much bigger [4500 iirc] 9 v cells as well so that may be another suitable alternative for longer use – not ideal though as you then need a charger for it.

    Premier Icon teasel
    Free Member

    So I’d be tempted to put a capacitor across that power supply (or battery) to give the extra heft. Some barely remembered A-level physics equations make me think that 1,000uF should be enough. I’d also chuck in a back EMF protection diode (don’t know if there’s much inductance in an injector but it doesn’t hurt).

    Okay, some of that makes sense from way back when I made a Velleman timer and fired off a relay via a capacitor and other things I can’t remember now. Thanks for that.

    I might have to go and do some homework before assembling this thing…

    E-mail manufacturers and get some info on the power

    Yep, I think you’re right. I might even see if the local motorbike place has one I can play with.

    Premier Icon teasel
    Free Member

    Thanks once again, guys.

    For once I appreciate your posts being rather lengthy, Junkyard. 🙂

    Premier Icon Junkyard
    Free Member

    EDITY: yes but not for the first time i got the wrong end of the stick and got all confused 😉

    ah scrap all that its to open the injector innit DOH i thought it was pumping the cleaner at high pressure

    Dont pay that price for it then do what Rich hall did
    IMHO a battery should work fine as its only used for a few seconds at a time
    I imagine its circa 6-10 mins of constant on from the battery- guess though

    Premier Icon twisty
    Full Member

    It really depends on what kind of injector you have.

    If you have high impedance injectors then you can hook up just about anything, a 9V battery, or some kind of regulated power brick 9-12V shouldn’t be too hard to find a spare one somewhere from an old printer, camera, scanner , modem, router, etc etc. I would be inclined to stick around 10V – as the injector is being held open rather than being pulsed pushing too much current through could cause it to heat up and burn out.

    If you have low impedance injectors then things are a lot tricker, as you really risk burning them out if you just connect those directly to a supply without using control circuitry to limit the current.

    The injector you linked to is probably using a little 9V battery because they can’t deliver more than about half an amp so won’t burn out low-impedence injectors.

    Premier Icon richmars
    Full Member

    twisty makes a very good point. We all assumed the suggested power supply may not have enough current available, but didn’t think that there may be too much! (Which may explain why they use a small 9v battery which doesn’t have much.)

    Premier Icon teasel
    Free Member

    Okay, so it’s looking like it might be wise to find out a little about the injectors before continuing.

    I’ll be back…

    Premier Icon twisty
    Full Member

    Oh and another thing I forgot to mention: if it is a one off job for a set of injectors then maybe consider posting it off to one of those places that cleans and flow tests them for a few quid. I did this and they reported back that they were not balanced even after cleaning, so a couple of the injectors were switched with 2nd hand ones to get all injectors flowing the same, and after that the engine was running quite a bit smoother and making more power.

    Premier Icon teasel
    Free Member

    That’s not a bad idea, though I did think about doing a bit of amateur spray analysis when they were being cleaned. I might investigate if any local firms do that sort of thing.

    One off job? Probably not, though it would only be about every 30,000. I recently read a service bulletin claiming it was an issue with this particular engine, though it suggested cleaning in-situ with some rather expensive air line driven equipment. The symptoms they list in the bulletin match what I’ve been getting – a slight flat spot around 2300 – and they suggest it’s this or/and the intake valves. That’s the next job once the injectors have been cleaned.

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