Fuel injector woes

[Mike]

Has anyone experienced this? The plastic tip of the fuel injector "fell off" into the cylinder. I heard a rattle, then bad noises. Went to investigate and noted a fuel leak at the base of the #3 injector (TWM set up). Pulled it, and lo and behold, no tip, just the o-ring and plastic 'separator?' hanging loose. Looked into the cylinder with a borescope. Walls and piston top look fine (what I could see of it). The valve area (exhaust) looked like it had black bubbly froth (hardened) around it. (compression test = 0 psi)
a) I can't believe this
b) trying to brainstorm my options, hoping to avoid pulling the head.

One thought is to remove the rocker so the valve and stem are free, let the valve slide down a little into the cylinder, then spray it through the plug hole with some kind of solvent that will dissolve the plastic/bubbly stuff. Twirling the valve stem might rub the valve against the valve seat and help scrape/rub off the crud if it's dissolved?????

Does anyone in this august body have any suggestions? Any chemical engineers know of a solution that will eat plastic and not steel and aluminum?

I reeeealy don't want to pull the heads...

Thanks,
Mike

 

[Ron Earp]

Whew, that is a new one. Never heard of a injector heading down into the intake port, and cylinder, but I suppose there is a first time for everything.

I don't think you are going to have any other recourse other than going for a head pull. I would suspect that valve is bent and the damage is done at this point, but your description of some black stuff in the exhaust area could indicate something stuck there and holding it open.

Unfortunately, the injectors by their nature being built to spray gasoline will be resistant to most chemicals I'd feel comfortable recommending to you. And, localized heating up of the area hot enough to slag that stuff off, even if you could do it, I bet would result in some head/valve damage.

Seems like there should be a way though and I bet someone might come up with a solution. If it were my baby I'd pull the heads, but this past year I think I've done four V8 head pulling and installing operations, so what is one more. I feel your pain and will continue to think on this one.

Ron

 

[Jac Mac]

Was told of it happening on Toyota MR2 recently. The piston came off 2nd best on that one. Sorry dont know of any magic solvents that would work. I know if it was a motor that I owned or was expected to warranty in any form I would not be happy until at least the heads were removed & checked. When this sort of thing happens on a hot engine the exhaust valve can be bent slightly, but the spring combo may be strong enough to seat the valve, however a few miles/months down the track the head of the valve drops off with $$$$$$ expensive noises.

Jac Mac

 

[Randy V]

Mike - I've not heard of the injector cap falling in like that before. The cap is usually bigger than the port due to it's rim. Sort of looks like a Derby-Hat.
Anyways - a couple of things.
If it happened on one, it may well happen on the others.

Your idea of lowering the valve might work better by removing the spring, then carefully lowering it and if you can see it from the spark-plug hole, you might be able to get in there with a micro-tip butane torche to burn the plastic into ashes..

 

[Chris Duncan]

"" noted a fuel leak at the base of the #3 injector (TWM set up). Pulled it, and lo and behold, no tip, just the o-ring and plastic 'separator?' hanging loose. ""

What brand of injectors?. You need to pull one of the other injectors, compare and determine what exactly fell off. Metal, plastic or both. A fuel leak indicates a "broken/bad" injector. I'd examine what may have caused this one to break, and maybe replacing them all with another brand.

""The valve area (exhaust) looked like it had black bubbly froth (hardened) around it. ""

normal soft carbon can look like black froth, you need to be running Chevron or any fuel with cleaner if you have build up.

""(compression test = 0 psi)""

that's not good, a leak down test will tell you which valve it is, more accurate than a comp test.

If a valves bent heads will have to come off. You could remove spring and spin valve while observing with borescope for runnout. There's also a possibility although not likely that plastic from the injector has melted onto the valve seat causing loss of seal.

The fact you heard noise isn't good and says "metal debris" to me.

""Does anyone in this august body have any suggestions? Any chemical engineers know of a solution that will eat plastic and not steel and aluminum?""

The plastic on most injectors is nylon. Don't know what melts that and not aluminum but there's probably something. The idea of a small propane torch might work also.

 

[Paul Thompson 'Hooligan']

Hmmm -

The pintle cover is exactly that as I understand it, a cover to protect the pintle valve tip from damage (most likely during handling or fitting)...

The loss of the cover would not adversely affect the use of the injector I think, however as other say, its consumption within the cylinder head / valve area is not good and I would also recommend pulling the head... especially as you are recording zero compression on the cylinder in question. A few hours now may well save a lot more (+ expense $$$$) later....

I have had one plastic cover 'pop-off' as I pulled an injector out of a Kinsler tb once, but fortunately the manifold was not on the head at the time and was probably caused by me not getting the pull exactly square to the injector locating hole and because the injector was somewhat 'stuck' from years of non-cleaning... (lubricate upon refitting)....

A leak showing externally on an injector will generally only come from the top (i.e. hp feed) end of the unit, where it fits into the fuel rail and remember, it is under pressure, maybe 45 to 75 psi so the slightest missfit, or damage to the seal may cause it to leak/weep. I have known some give a 'couple of drips' in total upon first pressurising a rail, but if they don't seal within a few seconds, then somethings not right! Always check as a leak of fuel at high pressure is definately to be avoided!

The fact that you have zero compression could be the reason the injector shows fuel at its base, as the base injector seal would normally only expect to see below atmospheric pressures on a n/a motor and only minimal pressures on a blown motor. If there is compression getting back past the inlet valve, with the throttle choke closed, there would be wide swings in pressure on the lower seal too, but still possibly not enough to force fuel past... Bottom line, if there's fuel showing, something ain't fitting right....

Let us know how you get on...

(ps attached a few pics showing the plastic bit (yellow) I think you are refering to, a typical pintle injector internals and a close up of the pintle itself - which is normally ground to tolerances of 1 micron and lifts about 0.06mm when open)....

 

[Mike]

Thanks for your ideas, gentlemen. It seems that although this is rare, it HAS happened.
Paul, the yellow cap in your pictures is exactly what came off.
I'm still fooiling with the %$#*& thing. When I get it resolved, I'll pass on what I learned for posterity.
Mike

 

[Joe T]

Mmmm, I think a head strip may be needed,

Does it still run?
How about taking the clearance out the offending exhaust valve, then a little bit more. Turn it over to make sure you still have piston clearance, then run it

Stick some redex through it, maybe the compression stroke and some cleaner might shift it or burn it off. Though to be honest I would have thought if it was only plastic it would have burnt off or gone soft enough for the valve to close properly anyway.

You do need to be up on your piston clearances, not for the faint hearted though.

Interesting