MFI Inj pump stroke

[apexerino]

I am currently in the engine phase of a rebuild of a 69 911 E targa. I have the injection pump off and am doing some cleaning of the metering injectors. I'm not sure if that is the proper terminology, but the parts that I'm talking about sit just under the fuel line connections on top of the injection pump.
These parts are cam driven...BUT... they don't all move the same amount... the stroke is MUCH different from one to the other..in fact..#4 only moves a miniscule amount. They are all free and unstuck.
My question: Should these units move the same amount? Are they hydraulic or something..so they need oil pressure to work correctly? I have read the technical articles and am using the Bosch instructions as I clean..but they don't mention this. By the way, the engine was running fine when shut down... 8 years ago.
Sorry so long, but thanks in advance.

Jeff

[Wayne 962]

Here's a tip - I recommend for fun, that anyone buy a junk MFI pump and take it apart to see what is on the inside. In many ways, they are more complicated internally than the entire engine. It really is like a Swiss watch inside these things...

I am not an expert on these pumps.

That said, I believe that all of the small pistons should rise and fall the same amount. It makes no sense to do otherwise. The fuel flow is controled by the rotation of the pistons (the corkscrew effect) which allows more fuel to be pushed through the lines. Theoretically, they should all go up and down the same amount, and should also turn the same amount too.

If you haven't seen it already, our Mechanical Fuel Injection Tech Section has just about all the info ever published:

http://www.pelicanparts.com/techarticles/911_MFI/TipMFI.htm

-Wayne

[power]

I post this as a warning to others not to back the MFI part load adjustment all the way out. I have seen this happen more than once. I have found the small spring from the part load adjusting mechanism (one of the parts that makes the "clicking" sound when adjusting) jammed in the injector piston spring you are talking about. This happend when someone had backed the adjuster right off the end. The other parts (adjusting crown and detent) were jammed in other parts of the pump!!!!! I am always weary of MFI injection pumps, when I cannot feel or hear the "clicking" noise when adjusting the part load adjuster. I know this is an old post and you probably have fixed your problem by now, just wanted to post possible warning.

[Wayne 962]

Good tip - also never make an adjustment while the engine is turning...

-Wayne