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Full Version V6 12v Injector Servicing

Club XM Forum > Petrol Specific Issues
I want to remove and clean the injectors on my S2 V6 12v as, as far as I know, they have never been done and it has 212k km on it. Can anyone advise the brand and model of injector and if there is a part number for a service kit?

I have access to an ultrasonic cleaner so that will make life a little easier.

Hi Craig,

Ive replaced the nozzle part of my injectors on both my XM's. Of course they are diesel as opposed to petrol. I've never seen a petrol injector taken apart so I can't really comment. There's nothing much to it once you've seen it done once or twice. Jus make sure the components go back inside in the right order and the right way around. There is one point to be made though. After reassembling the diesel injectors my diesel specialist pressure tests them and checks for the correct spray pattern in a jig. Ocassionally they don't give the correct pattern so he tries to reseat them by banging them on the side with a hammer. 8 times out of 10 this works and the injector behaves properly. However for the other 2 times he has to dismantle the injector again, clean and reassemble. This usually cures the problem. Without the test jig to check them I'm not sure how you can be certain that they are working correctly before refitting.

Whenever he dismantles an injector he always replaces the fire ring for a new one. The fire ring is a rippled spring steel washer which sits just behind the nozzle casing and the nozzle. It helps prevent the worst of the heat transfer from the combustion chamber back up through the injector. I would guess that the petrol injector has the same thing.

Overall, when handling the innards of the injectors you have to be extremely clean. The tolerances are such that the smallest piece of dirt will cause the injector to malfunction.

Having seen the nozzles removed from my injectors they were very badly worn both the pin and the injector hole in the nozzle. I'm not sure that just cleaning them without replacing the nozzles will help in any way. As I say, all of my comments are made with diesel injectors in mind and may not be applicable to petrol.


noz cool.gif
Hi Noz,

At the risk of being a little blunt, having spent a number of years on marine diesel engineering, if you have a diesel 'specialist' who uses a hammer to set injectors, I can tell you without fear or favour, you need to find a new place to go. These are items made to some of the closest tolerances on the entire engine. Either the engineer should have the correct kit to refurbish the nozzles (if specified by the manufacturer), or should be fitting new, matched components. In neither case should any form of hammer be part of the equation. For varying reasons, manufacturers set different spring rates for injectors on different engines and for new or reused springs. It is a fair test of a diesel refurbishing centre to ask what rate they will be setting your injectors at (preferably already knowing yourself what it should be). If they can't give you an accurate answer from information they have to hand, then go elsewhere. --- They won't bother to check specially on your behalf.
With regard to the heat washer you mention, for anyone not used to changing injectors, always take care to establish that the old washer is removed from the aperture. It is not uncommon for this washer to be left in place for more than one removal of the injector and it can become so flattened that it appears to be the actual surface of the head. A pointed probe with a slight angle on the end is most useful for checking the washer is out, working from the centre hole. Properly speaking, both this washer and the copper washer should be replaced if the injector is removed. The steel heat washer should be replaced with the corrugated ring facing up to the injector. The injector should not be tightened beyond the specified figure, as overtightening may cause the injector to malfunction. As with any operation involving the injection side, cleanliness is most important, so always ensure the injector recess is free of any debris.
I'm not really qualified to comment on petrol injectors, other than to say given that the working pressures are very considerably less than on a diesel system and they inject, relatively, at a much less critical point, then a greater degree of wear or poor pattern is of less significance. Of the few petrol injection cars I've had, I have a feeling looking at the injectors they are not a serviceable item.

Enough gloom for one night !

Hi Mike,

since u have so relevant experience, your opinion would be interesting on if all these products that go into the petrol/diesel actually do any cleaning job on the injectors, and to what extent this is comparable/different to a "mechanical" cleaning as discussed above.

Hello George.

On newer or lower mileage engines, I think a periodic dose of the relevant injector cleaner does help things stay sweet. On older or higher mileage units, no amount of pour in wizardry will fully compensate for mechanical wear in an injector or pump. Bear in mind that a diesel injector works in a pretty hostile environment -- high pressure, high temperature, exposure to combustion products and huge frequencies of high pressure pulses and snapping shut. Given that a badly performing injector can cause serious damage to the piston and surrounding areas, it does make sense to have them overhauled. Purely off the cuff, I'd say around 50k miles, but certainly if you've got to the typical XM six figure mileage. The good news is that to overhaul the straightforward mechanical type really shouldn't be that expensive (particularly if you can remove and replace them yourself). The units with the electrical connections are a different matter I believe --- I have to say I've sold my 2.5s when the smoke has become embarrassing, rather than stump up. Cleanliness is what it's all about with diesel, so don't skimp on the filter changes and make sure no nasties find their way into the output when you do the filter.
I've not had much to do with petrol injectors --- generally they don't look to be serviceable items to me, so the best bet has to be to stay on top of the filter and pour in a periodic dose of cleaner. I'm certain there will be others on the forum vastly more knowledgeable than I am on the topic of petrol injection.

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