How much movement from injection pump plungers?

[euroshark]

Hello all, I am fairly new to this forum and am just starting to dig into my 230SL that I purchased last fall.

The car sat for quite a while but luckily the previous owner had the foresight to drain the fuel tank. I have gotten the electric pump working and now I am starting to look at the injection pump. I started by removing the plate on the side of the IP and I could feel that three of the six of the plunger assemblies had a bit of vertical play but the other three weren't moving. I figured maybe the plungers that had some play were off of their "lobe" and the others might be at various points of lift. After rotating the engine by hand and wiggling each plunger they all started to free up just a bit but I feel like I'm getting maybe 0.5mm to 1mm of vertical movement out of them at the most. I've read a bunch here on freeing up stuck plungers but I can't seem to find any information on how much total stroke the plungers should have. I'm guessing that this little bit of movement is not even close so I probably have some work to do getting things un-stuck. Any information would be much appreciated.

[ja17]

Check the rack. If it does not move freely then you have stuck piston or pistons. Yes, pistons (plungers) move quite a bit more than you indicate. My guess would be around 8mm plus or minus. Find out which cylinders are moving. You can remove the injection lines at the pump. Remove spark plugs and depress throttle to full and crank the engine to see which cylinders of the IP are producing fuel. The fittings in the top of the pump must be torqued to 18 ft/lbs. before fuel will pass the check valves. If you find some are not pumping fuel remove the fitting and the check valve to see the stuck piston. Soak and free up until the rack moves freely and all cylinders producing fuel.

[euroshark]

Thanks Joe. I got all six plungers moving now using a combination of B12 Chemtool and Kroil and tapping the plungers down with a golf tee. The rack moves fore and aft now and I can watch all six plungers come up and back down as I rotate the engine by hand. The rack takes some effort to move, maybe similar to dragging a spoon through a jar of honey, and I suspect that this is probably too much effort.

Do you think i's reasonable to expect the rack and plungers to loosen up further once I pump some fuel through the IP? So far all of this work has been done without pumping anything through the IP. I've just been adding solvent and penetrating oil to the tops of the plungers.

[euroshark]

Update: Acetone did the trick. Flushing each cylinder out with fresh acetone, rotating the engine 90°, move the rack back and forth through it's full range a dozen or so times, and repeat. Took roughly 45 minutes. Now the rack moves easily and returns to center on it's own when starting from either extreme. Next step will be installing a temporary fuel pump, replacing soft fuel lines, changing the oil and replacing the filters. This car has been sitting for a very long time but the engine turns over nicely and I can feel and hear compression with each revolution so I am pretty confident it'll be running soon.

Note to anyone going through this process, there are multiple references on this site to the threaded hole in the end of the rack as being M4. My car is a 1966 230SL with an R11 pump and the hole is M5x0.8 which is interchangeable with #10-32.