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testing Injectors before connecting to Megasquirt


landybehr
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Hi,

I am about to put the fuel rail back onto the engine. I have a set of 4.6l V8 - type injectors that are new (ebay) but I´d obviously like to see them spray before I bolt them in.

I might try to do the following things - and write here to give you a chance to stop me before I do sth. silly .. ;)

Ok, I want to take one of these portable containers with which you distribute herbizides etc. in the garden. This is filled with Ethanol (white spirit you call it?) and connected to the fuel rail and then put under pressure (might use the air compressor to help). If I think about it I could even take a length of hose, connect it to one injector at a time, fill in some ml´s of fluid and then connect the hose to the compressor (being set to 3.5bar) - sounds easy, doesn´t it ?

Then I connect the injectors to a 12V battery for a few short bursts and look what happens.

I presume that the Bosch injectors I am talking about are high-impedance onces and hence can be given a real 12V supply !!???

(I have collected all the necessary data i.e. flow rate etc. via google. So I can provide MS with everything it needs to know about the injectors. Just need to see that each of them is working. I could re-use the old 3.9type injectors but would have to clean them (no problem) and still want to check them any way. I do not have MS set up to use it´s injector test mode, but feel that it wouldn´t give much of an advantage over the above procedure ..).

What do you think ???

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from my college days I remember Injector testing being one of those things a specialist piece of equipment was for

like a space helmet in plexi glass so the spray pattern could be seen.

the foot note being the injector spray could pass into the bloodstream through your skin, so a back garden test may have some worrying side effects.

try ad rig something the fuel can spray into so as to minimize any risk to yourself.

a cola bottle or similar can withstand 150psi apparently.

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yeah thanks,

the danger of skin penetration probably applies to diesel-injectors. They have much much higher pressures.

I think the 200/300 tdi injectors work at 220bar ??? (IIRC). Modern common rails 5-8times of that.

The fuel pressure in the V8-fuel supply line is kept at around 3.5 bar.

The 3.5 bar is a pressure that´s lower than the pressure in the cold/hot water supply in our house.

Disclaimer ;) => I think main danger is generation very flammable fumes. I am aware of that and will do it outsides.

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Yes, you can test them………… fuel rail pressure is 37psi (I think 2.4 bar)

You will need to use the regulator on the fuel rail to regulate the pressure …………. The vacuum connection is only needed to lower the pressure at idle and over run.

Its only early 3.5L flapper injectors that were low resistance ………….. all hotwire and later injectors are 12V…………..

I usually apply 12V to a cold injector to and listen for a click (solenoid noise) ………. That usually tells me they are OK.

If you think about the way in which the injection system works (alternate banked)................. 2 banks of 4........... then the spray pattern is not that important and fuel is dumped into the inlet manifold and left there to atomize until required ;) .......................... a good spray pattern is much more important for sequential injection.

:)

Ian

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a cola bottle or similar can withstand 150psi apparently.

For interest, yes that's true, tried and tested with a gauge.

They seem to suffer from fatigue though, after about 5 cycles it popped at less than the 160ish i originally had it at.

Made quite a bang when it went......

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Hi,

good news about the 12V,

I am not so sure about what you wrote about the inlet manifold.

I am aware that the injectors are triggered bank-wise, but each injector will spray into an individual port of the inlet manifold as close as possible to the inlet valve. If one injector is clogged I doubt other injectors will substitute that, think of the strong flow of air being sucked in by a piston at high RPM´s. I fear that one partly clogged injector leads to a lean mixture in the corresponding cylinder. Well, even though there may be some strange flow of air in inlet manifolds - I´ve been told by a friend that he once accidentally dropped a small spring washer into an inlet manifold of a V8 without noticing. After a few miles after first startup the engine made noise. When the engine was disassembled again the washer had been smashed into several pieces and 4 pistons showed signes of damage by parts of the washers. Amazing that things that once get into a cylinder manage to return into the inlet manifold and then reach other cylinders .. !

Cheers,

Hendrik

Yes, you can test them………… fuel rail pressure is 37psi (I think 2.4 bar)

You will need to use the regulator on the fuel rail to regulate the pressure …………. The vacuum connection is only needed to lower the pressure at idle and over run.

Its only early 3.5L flapper injectors that were low resistance ………….. all hotwire and later injectors are 12V…………..

I usually apply 12V to a cold injector to and listen for a click (solenoid noise) ………. That usually tells me they are OK.

If you think about the way in which the injection system works (alternate banked)................. 2 banks of 4........... then the spray pattern is not that important and fuel is dumped into the inlet manifold and left there to atomize until required ;) .......................... a good spray pattern is much more important for sequential injection.

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BTW:

The more I think about it: May be it´s just as easy to buy a color-tune spark plug. I guess the flame picture will be different if a injector is faulty. That can be checked at certain inspection intervals.

But first I will do the 12V - listen for click - method as suggested by BullBarCowboy !! And then re-think if all the hassle with hoses and pressure-testing of injectors is worth the effort.

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