Calling all MFI gurus

[wkershaw993]

All MFI gurus,

After reading almost every MFI thread I am still slightly confused and looking for any insight from you.

I've downloaded and read CMA multiple times, read Lee Rice's procedure, CMA-2, etc...

after inspecting the car (71 S) it seems as though the pump lever is not resting on its stop. It seems to me the stops for the butterflys are holding it back. All 6 butterflys leave their stops at the same time.

If i disconnect the linkages that connect the crossbar to their respective sides the pump lever will fall back onto its stop. Am I correct in assuming this is incorrect and the pump lever should be resting against its stop when the throttle is at idle? (no preload on the pump lever if you will)

Thank you in advance,
Will

[wkershaw993]

Here are some pictures to help clarify what I mean

This is with all the linkages connected




This is with the linkages disconnected

[Richy]

All levers should be on their stops . The rod for the MFI lever should be 124 mm and the other rods adjusted accordingly as per the last technical bulletin . The pump will probably need adjusting after this change .

[Arne]

Edit - corrected the wrong spec I repeated from above. I would add that if the rod from the bell crank to the pump is already correct at 114mm, then the rod(s) from the bell crank to the throttle plates are wrong.

[jashford]

From Check Measure Adjust

"Adjust the rod between the pump regulator lever and the cross shaft precisely to the measurement of 114 +- 0.2 mm"

[2.5MFI]

114mm is correct. Not 124mm. Jashford is correct.

[wkershaw993]

So the pump lever is NOT in the correct resting point in this current set up, correct?

The link from pump to cross-shaft is at 114mm. I’m guessing the linkages from cross-shaft(bell crank? Same thing?) are set too long.

And changing the length of these in order to get the pump regulator lever on its stop is going to skew the whole “fueling table” lean.

Is it possible to set the part load mixture without having a set of protractors? If it is, how would one set the throttle at 7-degrees as stated in the CMA?

Thanks again guys, this forum has been irreplaceable

[gled49]

Start by removing 2 rods to each side of throttles, u said throttles close on stops. Remove pump rod, measurement is 114mm center to center, reinstall rod. Now loosen jam nuts on the 2 throttle rods and install with no preload. That is your starting point. I set mixture by driving and adjusting richness just above lean surging. Been doing this 40 years and have developed a feel for it. U will have to adjust mixture however, with or without help. Condition of engine, throttles and pump will determine next steps.

[jashford]

You are right. The pump lever is not in the correct resting point. If the pump rod is at 114 mm, ball center to ball center, then you need to adjust the other rods keeping the pump on its stop and the throttle plates at rest.
I've never used the protractors and everything seem to work well for me.

Best of luck, John

[Richy]

My memory was obviously incorrect , 114 is the dimension . Next time I will cheek before posting , and I think Porsche's last tech bulletin essentially eliminated the need for protractors .