Stuck injector removal

[Mechanos]

Trying to get the injectors out of the engine in my 955. The service manual suggests using a fitting nut from "an old fuel line" to make a puller to use with a slide hammer. Well, as luck would have it, I'm fresh out of "old fuel lines" laying around. Anyone happen to know what the thread size and pitch are on this fitting nut? If I can source something locally that will thread onto the injector, I can fab up a puller.

[rswyan]

I'm not familiar with that engine in particular, but I just had to pull the injectors on the Mercedes 5 cylinder diesel in my van recently. They are secured in the head by hold-down bolts that run down thru a clamp that is shaped like a "V" lying horizontal that surrounds the injector.

The way I got them out was to warm the engine up real good, shut the engine off ... and then loosen the injector hold-down bolts, so that there was a full turn or two of slack after the bolt head rose above the V clamp ... maybe 1/16" of play or so between the bolt head and clamp. Then start the engine back up and run it a bit (including driving the vehicle in our driveway) until the compression of the engine pushed the injectors up in their bores.

Worked like a charm

[Mechanos]

I did try to use the engine compression to pop it out by turning the engine over with the starter, but I did not try to run the engine with the injector hold down loosened.

[rswyan]

I did try to use the engine compression to pop it out by turning the engine over with the starter, but I did not try to run the engine with the injector hold down loosened.

On the engine in my van, two of the injectors "popped" shortly after starting it up after loosening the bolts.

The next two didn't pop until I took the van up to the straight portion of the driveway and made like I was at the strip doing the quarter mile from a standing start.

The fifth injector never did pop - even after a 54 mile roundtrip most of which was on the expressway. I checked the injector right after that though and I was able to easily turn it in it's bore. After working it back and forth a little, it lifted out easily.

I have a wrench/ratchet/socket ready to tighten the hold-down bolts if you do this ....

[Mechanos]

Decided to take one of the injector line off and head into town to try and match up a fastener to determine the thread size on the injector. 1/2" is too big, 7/16" is too small... as I figured, it probably metric. An M12 x 1.75 bolts seemed to thread into the nut on the fuel line perfectly, so I bought an M12 x 1.75 nut and an M10 bolt that fits into my slide hammer and planned to weld to the two together to make a puller. When I got home, I tried to thread the nut onto the injector to verify it fits and it doesn't. It will start and turn about a 1/2 turn and stops... gets very tight like thread bind. Got out the calipers and measured the thread diameter on the injector and came up just a hair under 12.5mm. So it looks like it's some odd ball thread and no "off the shelf" fasteners are going to work. Looks like I might have to break down and buy the Yanmar tool since I don't have any extra fuel line nuts.

[dminer]

Have you tried some of the flare nut and compression nut fittings? Also, is there a chance that it is 3/8 pipe straight thread?

[Mechanos]

Haven't tried any flare nuts or compressions nuts. Don't think it's 3/8 pipe as the thread diameter for that is 0.675" which greater than the 12.5mm I measured. Also, 3/8 pipe is 18tpi... a metric 1.75 pitch appears to thread correctly. I believe metric 1.75 pitch comes out to something like 14.5tpi.

[Mechanos]

The Yanmar tool available through a Yanmar distributor is $30. I feel like I've already spent that much in my time jacking around trying to figure out what thread this is. Kinda feel like I'm spending a dollar to save a dime. At this point, I'm just going to order the tool and be done with it. I'm not loosing any time by waiting on the tool to be shipped as I found out today that the compression tester adapter I order is on back order and will not ship out for about a week. In the meantime, I'm going to removed the hold down plates, clean any crud out of the groove around top of the injector bore and the injector body. Then hose the injectors down with some penetrating oil so then can be soaking and loosening up...hopefully.