Fuel Inject Pump Throttle Lever to Rack

[JohnnyC]

Hi,  I have the side cover to the FIP removed to expose the rack and plungers.

Question..., when I move the throttle lever off the idle stop, the rack to the plungers does not move aft. By hand I can rotate the linkages (CW) and the rack freely move aft, (plungers do not move up/down) and the rack returns to forward position. 

Is this a normal condition? 
Is the throttle lever on the FIP directly connected to the rack?
Does the counterweight move the rack?
Are the plungers supposed to move up or down as the rack moves fwd/aft?

I have also been reading the Tech Manual (published here) and the BBB.

This FIP is installed in a '70 280SL.

Thank you, Cheers and God Bless,
JohnnyC

[ja17]

The rack is not a direct connection. It may move more or less depending on RPM, engine coolant temperature, barometric pressure and throttle position. However it should move a small amount, with the engine not running with full movement of the linkage lever.

[wwheeler]

That is a complicated area to be sure. I do not believe there is a direct connect to the rack from the throttle lever and the connection goes through the governor. Engine speed plays a part on how much the plungers rotate given input from the throttle lever. With greater engine speed, the more effect the throttle lever has on the rack and the more they rotate to let more fuel in. So it is entirely possible that the rack will not move when the engine is not rotating although I would think it should move some. Never seen to be sure though.

Conversely, the starting solenoid does have a direct connection to the rack. So when it moves and rotates the plungers to make the mixture more rich during starting, it is direct. 

[JohnnyC]

Thank you so much JA17 and WWheeler, much appreciated.

Cheers and God Bless,
JohnnyC

[Fonzi]

I am working on my first mechanical injection car and for this same question joined this sl113.prg group even though I don’t have a w113.  My rack does move a little with the first part of motion of the throttle, but stops moving after just a bit of motion.  The rack moves freely and I have no reason to believe anything is wrong, but I had a very hard time verifying that.  It is not yet verified.  I bolted it back on the car and have yet to get the car running, but need pressure from the fuel pump I think, plus I had fried points. 

[ja17]

Sounds like your rack is ok. If you had the fittings on top the pump loose, (the ones the injector lines connect to) they must be torqued to the correct value or pressure will not develop. Allow plenty of cranking to fill the empty injector lines, since only tiny amounts of fuel are pumped with each stroke of the pump. I remove all spark plugs, so cranking the engine is easier and faster, until the injection lines are primed.