Ultrasonic cleaning of injectors - what solution?

[zcacogp]

Chaps,

Not sure whether this should live in GG, Homes Gardens and DIY or here ... so it has ended up here!

I have an ultrasonic cleaning bath. I have a car with injectors that have done 150k miles without attention.

I'd like to clean the injectors in the bath.

What solution should I use? And can anyone suggest a way to produce a 50hz(ish), 12v, square wave (ish) signal to pulse them while they are being cleaned?


Oli.

[GreenV8S]

Unrectified output taken from a mains->12V transformer, maybe? Or make/borrow/steal an oscillator and use that to control a relay.

[hidetheelephants]

I don't really see the point if there's nothing being forced through them; most cheap DC socket mounted powersupplies produce a fairly lumpy output, or you could get one that just puts out lovo AC. A slightly more sophisticated way to do it would be to get a signal generator off fleabay and create a driver current with a simple transistor amplifier/driver circuit. Are injectors safe with a reversed polarity? If it damages them, then putting a diode + resistor in parallel with the injector will provide protection.

ETA most of these cleaners seem to use nothing more aggressive than soapy water; you could try meths or paraffin, as I don't fancy getting water in injectors. Have a fire extinguisher handy.

Edited by hidetheelephants on Thursday 8th October 23:55

[TheEnd]

I'd have thought carb cleaner would be ideal.

[zcacogp]

GreenV8s, yes, I was thinking about the output from a cheap car battery charger; I bet that is a 240v -> 12v transformer, with a rectifier stage bolted on the end. If you could take the output pre-rectifier then that would do nicely. Alternatively an oscillator driving a relay would be a good idea - I hadn't thought about that.

HTE's - Thanks. Yes, I was wondering about rigging up a small pump, recirculating the cleaning fluid from the bath through the injectors while they are being cleaned. You'd need a filter in there as well, otherwise you would quite probably pick up some crud from the bath and ruin the injector completely by forcing it through, but that wouldn't be hard. If you had a pump you could then flow-test them afterwards, inspecting the spray pattern and measuring the rate of output (time to run 100ml through them for example, and compare them all with each other.) That would get quite sophisticated ... what sort of pressure do injectors run at? Couple of bar. I don't know about the reverse polarity question, but I know a man who probably would know ... Snag is that the cost of this caper needs to be less than the cost of having them professionally cleaned - and preferably a LOT less. The cleaning bath was free (it was broken) and currently I don't have much cash.

TheEnd - yes, I was thinking about carb cleaner. I'm with HTE's on not wanting to push water through them. Apparently putting flammable fluids in a ultrasonic bath isn't a good idea, but it is OK to put them in a (glass) jar which is then placed in the bath, with water around the jar as an acoustic coupler. I was contemplating acetone, but that's perhaps a bit too flammable (explosive vapour). Paraffin would be another suggestion; it's a good solvent but doesn't burn that easily. One to do outside I think.


Oli.

[fergus]

zcacogp said:

what sort of pressure do injectors run at? Couple of bar. Snag is that the cost of this caper needs to be less than the cost of having them professionally cleaned - and preferably a LOT less.

Can run between 2 and 5 bar, depending upon the type and flow capacity

The problem with doing this yourself is that you have no easy way of rectify flow issues, whether that be flow pattern, flow rate, etc, unless you have spare pintles, nozzles, seals, etc?

I don't think it's that expensive to get them cleaned and flow matched professionally? Give Dave Walker at Emerald a call for a price as he's pretty good and has an ANSU machine to do the job!

[GreenV8S]

I found it quite easy to test the spray patterns and measure the flow rates just by taking the fuel rail off (injectors still in place), powering the pump and switching the injector on with a separate supply. It only needs a simple jam jar to catch the petrol. Just be aware that this produces a noticeable amount of petrol vapour so make sure the electrics don't produce a spark anywhere near them - use proper connectors and switches etc not just something bodged together. And make sure the area is well ventilated while you do it.

Alternatively, you could quite easily set up a separate system off the car with a fuel supply, pump, tee piece feeding the injector[s], and a regulator back to the tank. It's a simple DIY and would only need a few quid in parts, plus the pump & regulator.

If I was going to the trouble of cleaning them in a sonic bath I think I'd set the flow tes up and then just immerse the injector in the bath. But I'd want to measure the flow and test the spray pattern first to see whether there was any problem in the first place, and make sure the cleaning has fixed it. It seems a bit silly to go to all that trouble otherwise. Also consider getting an injector service kit and replacing the O rings, pintle caps and basket filters while you have them out, the parts don't cost much.

[zcacogp]

GreenV8S said:

Alternatively, you could quite easily set up a separate system off the car with a fuel supply, pump, tee piece feeding the injector[s], and a regulator back to the tank. It's a simple DIY and would only need a few quid in parts, plus the pump & regulator.

If I was going to the trouble of cleaning them in a sonic bath I think I'd set the flow tes up and then just immerse the injector in the bath. But I'd want to measure the flow and test the spray pattern first to see whether there was any problem in the first place, and make sure the cleaning has fixed it. It seems a bit silly to go to all that trouble otherwise. Also consider getting an injector service kit and replacing the O rings, pintle caps and basket filters while you have them out, the parts don't cost much.

You're thinking along exactly the same lines as I am. Where can I get an injector service kit?

2-5 bar? Thanks Fergus. I suspect that the best pump is going to be a second-hand automotive one anyway, which will probably produce the right pressure.


Oli.

[GreenV8S]

zcacogp said:

I suspect that the best pump is going to be a second-hand automotive one anyway, which will probably produce the right pressure.

You won't need much flow so any EFI pump from the parts bin will do, but you do need a pressure regulator too. I'd suggest going for the same pressure the car runs at (i.e. the nominal pressure without a manifold reference).