[Bulti]

I just found out that a very good reason would be that, after about 23 years, the green plastic caps desintegrate when you pull the fuel rail off of the engine. The plastic bits have disappeared into the abyss. I got some of them out, but I'm not sure every piece is accounted for.



Let me guess, pull the intake manifold? Or leave them be?



What say you, oh mighty forum members?

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[Lear35A]

I'll give it a go.

I don't think little bits of plastic that may have fallen into the intake manifold could cause any problem. They'd either sit at the bottom of the intake manifold and do nothing or be sucked into the combustion chamber to be vaporized.

Look at it this way. If you'd have a shop change the injectors, even a very reputable one, do you honestly think they'd pull the intake manifold at their expense?

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[Bulti]

I was hoping somebody would say my car would be able to 'digest' the plastic, lol.



What the shop is concerned: if it would be harmfull and if they would risk such a thing I guess they would be insured for stuff like that. I on the other hand would be very much screwed.



Anyway, the 'vaporizing' bit is kinda reassuring :-)



I wonder if my mini-MagLite that I dropped in there would also vaporize? Mmm...

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[flash]

maybe. maybe not. not so sure that plastic will burn. it might just melt and become very hard little balls. after all, it is designed to hold up to high temps and fuel.



i don't think it's going to sit and stay in the manifold. after all, the manifold is designed to get everything out of there.



another concern would be getting stuck in a valve and bending the valve.



i'd pull the manifold. it's only a couple of hours off and on, and sure would bring some piece of mind.

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[Bulti]

You just ruïned a perfectly good evening Flash. Now I have to stop being lazy again. Damn you piece of mind, lol.

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[flash]

lol - i know the feeling. i just had to do this not long ago on a car i was working on. the danged o-ring broke and pieces fell into the manifold. i had no way to get them out. pain in the butt, especially considering i had just finished the supercharger installation, and then had to remove it in order to get the manifold off.



maybe the pieces would have been ok. maybe they wouldn't. i just didn't want to risk it.

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[Lear35A]

OK, so I'm only a chemical engineer USC '70. But it's pretty hard to imagine a polymer not decomposing in an oxidized environment with a flame front temp in the 3800degF range. Your bit of plastic (should it get anywhere near the combustion chamber in the first place) may reside in a molten state for milliseconds, but it's also hard to imagine that transitional state bending a valve. OTOH I can imagine many scenarios of problems created doing an R&R of our ungainly intake manifolds!

So pick your piece of mind where you want it and have a good evening.

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[parptarf]

Flash, the "ruiner of evenings". Oh pity us who have you and your infinite wisdom. <img src="/forum/images/smilies/968/wink.png" class="smilie" alt="" />



Thanks for the tip Bulti! (And Flash)

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[flash]

lol - i'm just not sure. i don't like making assumptions. i've seen crap hiding in there before. i've bent valves on other engines from valve seals coming apart and getting into places they shouldn't. since these items are specifically designed to withstand their conditions, it stands to reason that they would be pretty tough.



as for combusting, i don't think they would instantly vaporize. if they do burn up, it should take a little bit, depending on the size of the piece. given that our engine is an interference engine, it would only take one stroke of the piston to bend something or do damage.



i'm not saying lear is wrong. he could very easily be right. i'm just not sure i'd want to risk it.



as for complications, R&R is pretty easy. not much to go wrong, though i suppose anything can happen. you could drop a bolt, strip a hole, yada yada.



sorry i don't have a definitive answer. i just tend to err on the side of caution. lol - guys like lear, who have the facility to do it, may like taking his motor apart just for giggles, but i don't.

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[Lear35A]

We do it, but we don't like it.

OTOH, I haven't touched anything in 18 months/5,800 miles except 2 SC belt pulleys. And it runs GREAT. <img src="/forum/images/smilies/968/clap.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/clap.gif" class="smilie" alt="" />

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[Cloud9...68]

I would think that by contacting either Bosch, or even possibly a reputable fuel injector service company, you could find the type of plastic that was used for the plastic caps, and then look up this plastic's properties. If its melting point is well below the combustion temperature of gasoline, your're probably safe, because even if they wouldn't vaporize, they would probably get soft quickly enough to not do any damage. But of course, even this isn't a guarantee.

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[paulzebo]

How about a close up of the injector tip? I would pop the cap off another and compare the tips before a tear down. If it has a carbon build up, the cap probably left some time ago. You should replace all of them anyway at this stage.

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[Bulti]

Sorry Paul, they are already being serviced. My guess is though, that the cap fell off while pulling the rail (I think the tip was still white). The o-ring was stuck into the manifold too. But that's only a guess.



To be honest, after some reading up, I'm not that keen on pulling the manifold anymore. There is maybe a risk involved, but I also need to fix the leaky balance shaft seal and I'm kinda ready to drive the thing for a change.



My plan of action: taping a small diameter flexible hose to our vacuum cleaner and try to remove any left behind pieces. This way I can at least minimise the risk.



As the plastic's heat resistance is concerned, does the intake manifold handle the same high temps as the inside of the cylinders?

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[paulzebo]

"As the plastic's heat resistance is concerned, does the intake manifold handle the same high temps as the inside of the cylinders?"



[color="#282828"]Not even close. If I recall correctly, the temperature during combustion is around 3000 degrees F. I like your plan, but should you hear a rattle noise on startup, it's time to reconsider.[/color]

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[Bulti]

The first startup will be pretty exciting, that's for sure :-)

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[Lear35A]

[quote name='Bulti' timestamp='1409074126' post='161615']

The first startup will be pretty exciting, that's for sure :-)

[/quote]

Nah. My prediction is a complete non-event. <img src="/forum/images/smilies/968/laugh.png" class="smilie" alt="" />

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[Bulti]

I like non-events. A lot! Lol

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[MCL968]

What about pressurizing the cyl and blowing the pieces back through the intake manifold? All you would have to do is arrange the crank to open the intake valve.

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[Bulti]

I'm not sure I'm following you. The pieces should be still inside the manifold? Please enlighten me, before I ask a whole bunch of stupid questions (probably too late).

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[MLB]

Well, I just removed my injectors tonite, "while I'm in there" for inspection of the cam chain and pads (just under 90K on the ODO).

Here's a picture of the tips of 2 injectors. The other 2 looked much the same, sorry to say. Whoa.



So, those of you who have dared to look into the abyss of a dirty injector before:

would you classify this as "OMG, does your car even run!?" or is this a "normal but ugly level of dirt", and will I experience a new level of low-end grunt, after I have them cleaned and flow tested by RC Engineering?



   

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