Pulling 3GM30F heat shield and precombustion chamber

[walmsleyc]

This question applies to all the GM and HM engines (and perhaps more that use the same style injectors).

I have removed my injectors so they can be cleaned, serviced and calibrated. If any of you have done this, it's pretty straight forward to remove these.

But, hiding under the main injector bodies are 6 separate pieces (large copper washer, insulating gasket, heat shield, copper washer, pre-combustion chamber, copper washer in order from top to bottom). The "heat shield" and the "pre combustion chamber" are substantial metal bits (as opposed to copper washers). According to my "Seloc" manual, all of these part should be removable without much more than a pick tool and some fiddling. Others have reported challenges removing these parts.

I have 2 of 3 "heat shields" out and none of the "pre-combustion chambers" out. The ones that did come out did so with only a little bit of fiddling and a firm pull with a pick. I think there is a little bit of corrosion around the one remaining "heat shield" and I suspect the "pre-combustion chambers" a sooted in place, and maybe one has a bit of corrosion as well.

Anyone who's worked with GM injectors probably knows the parts I'm talking about.
(See picture with red dots shows the items in question).

So, the Question is: Does any one have suggested approaches or suggested tools to help extract these pieces?

I could remove the head, flip it over, and push/tap these from the "inside" of the cylinder (obviously a much bigger job). I could leave the "pre-combustion chambers" in place and hope their associated copper washers are still good (not recommended by mechanic) and replace all bit the last(bottom) washer.

Appreciate any suggestions.

Chris

 

[DJAY]

You will not get the lower precombustion chamber out without cylinder head removal and probably a hydraulic press. Leave it alone if you can. If the engine started easily and ran well there is no problem down in there. The next copper washer and the upper portion of the pre-combustion chamber should come free with relative ease. Any sort of probe with a curled/bent tip should assist extracting it/them. The heat shield is under a very thin copper cover... I peeled it away with fingernails. The heat shield itself is a graphite infused metal core that will come out in pieces from a recess in the upper portion of the pre-combustion chamber. Simpler to do than explain here. The O ring (rubber compound) is there simply to keep water out of the injector pocket. When finished, bleed from primary fuel filter to engine fuel filter to injector pump. Then, bleed at fuel inlet line to injector, not at fuel return line.

 

[walmsleyc]

Thanks djay,

The #1 cylinder upper chamber is resisting because the o-ring on the injector was shot/split. A bit of water must have gotten down in there and created a bit of corrosion. The injector bore is definitely rougher that the other two.

As you suggest, I'm leaning toward leaving the lower chambers in place. My plan for removing the final stuck upper chamber is a blind bearing puller. I found one on amazon with a collet small enough for the hole in the upper chamber.

I've got the heat shields off the first two, and once you can get something under an edge, they do pop out.

Thanks for the advice.

Chris

 

[NYSail]

On my hm I replaced all washers and heat sheilds and left combustion chambers in place. Used a pick to get everything out but was careful not to get debris down into engine...... stuffed tissue in to block then vacuumed. Engine ran like I dream. I was told if you want them out without removing the head to put injectors in loosely and turn over engine and the compression with dislodge them. I didn’t have the coconuts to try and just let things be..... in the end all worked out well.

Good luck

 

[Whatfiero1]

Mine had one stuck too I left it and still did a compression check with compression tool from harbor freight. new injectors my 2gm20f starts right up now in cold weather

 

[walmsleyc]

I've heard that trick about using compression to pop out the chambers and also don't feel the need to try that. I think I will run with the idea that if the bottom chamber hasn't budged one iota, then the copper washer that I can't get at it is probably still doing it's job.

I just did a compression test and all cylinders read 340psi. As far as I can tell, that is factory spec. Anyone know for sure what the compression spec. is for a 3GM30F?

 

[walmsleyc]

Well I found a "Blind bearing puller" on amazon that had one collet with a range of 6mm-8mm, and this fit inside the hole of the upper chamber. Using the slide hammer it came with, and about 10 gentle slide/taps it came out. No damage to the top chamber at all. I think I will leave the lower chambers in place with the expectation that if they weren't disturbed, then the copper compression washers under them will still do their job.

 

[DJAY]

You should be good to go. Here’s a photo of a heat shield removed, perhaps with very little grace and finesse.

 

[walmsleyc]

Yup! .... That's what mine looked like. The insulating graphite/steel washer comes out, like yours, as a messy crumble of bits. Took a little bit of fiddling to pop it out then I used a combination of gentle scraping and a dremel with small wire wheel to clean it up. Mine look ready for another 30 years! Now just waiting to get the injectors back from the shop after inspection and calibration.