3 stuck plungers on the MFI pump

[Shab]

So, I think I have 3 stuck plungers on the MFI pump on my M129. I have all the classic symptoms from what I have read here and on the Pagoda forum. Plus when I crank the engine, I don't see any movement. This relates to my thread "M129 unresponsive to tune up".

Question is, where to I check the rack for movement while trying to un-stick the plungers? (See pic) At the red or green arrow?

Many thanks.

[Arthur Dalton]

The rack turns the plunger to meter the fuel, but if the plungers are stuck in the top position, the trick is to remove the check valves on top of the plungers [ need a threaded fitting to do this] and then use a carb/gas cleaner to soak them from the top.. You can push them with a soft piece of wood [ I use a golf " T", seeing they don't work well for me on the golf course].
It is the pump cam that pushes the plungers up/down, not the rack..the rack rotates them a the number of degrees needed to meter the correct amount of fuel. Exercising the rack will help turn the plungers a bit , but if they are stuck up, you have to move them up/down to free them,and rotating them with the rack does not do as good a job as actually getting right to the plungers themselves...from the top

[Shab]

Thanks Arthur. I'm on the right track with the golf tee (going to see my neighbor to get one). I also want to get a sense of the rack movement so where do I grab hold of it?

Also, any idea on this "threaded fitting" I need to get at that last piece?

See pics...

Ps. Everything has had a good 2 + day soak with Aero Kroil, carb cleaner and a shot of Sea Foam "Deep Creep".

[Arthur Dalton]

The rack on that pump has a threaded hole in the end under that black plug..4MM thread [ although I have also seen 5mm] ..you thread a screw into the rack end about 40/50mm long and then you can exercise the rack [ foward/backwards], while you push the plunger down w/golf T ..You have to turn the pump over a few times so you know the cam that pushes the plungers is down as you push the plungers , or else you yo could just be pushing against the cam, ya know ??? Just try different posistions....
That should free everythng up ....let all the parts soak good and don't force ANYTHING....
That pump is an early one with cone check valves , so you do not have to remove the Ball checks like you do on the later pumps [ they connverted to ball valves right after that pump b/c the cone valves would leak back and the lines would drain, resulting a bad starts after sittng]
The newer Ball checks can be fitted to that pump, need be............

[Shab]

Just a note to report I'm getting nowhere with these plungers. May be time to throw in the towel and seek professional help. Nothing will budge.

Could they just as easily be stuck in the down position?

Any advise would be appreciated.

[bwostosh]

I have a bunch of spares for that pump and 4 good pumps too.
I've recently organized my piles and know where most parts are.
Brian O.

[Shab]

Thanks for the info. When I'm ready to throw in the towel, I'll get in touch.