All I know is there are several professional rebuilders out there who can't seem to get it right. Good luck.

This is an exquisitely designed (appears very simple,but is not) fuel distributor. Here is the problem--the unit has to feed each injector the identical fraction of the total fuel flow over the entire range of total fuel flow--from less than 1 gal/hr to over 50 GPH. To accomplish this, each 'metering assembly' has to achieve the same pressure drop as all the others over the flow range. (All this assuming each injector has the identical flow characteristics as well.)

This entails adjusting ALL the metering assemblies so the base pressure drop and the running pressure drops for each assembly all follow the same curve--flowing the identical amount of more fuel as the pressure increases. The CIS adjusts fuel flow with a 'mechanical/hydraulic' link bewteen air flow (the saucer plate in the intake horn senses air flow) that raises the fuel pressure to the fuel distributor as air flow increases. This requires that each piston and spring have the identical force vs displacement characteristic and that each piston have the same 'drag' in its bore,etc., etc.

Each and every part,component, and adjustment HAS to be perfect for this to work. They do-when new and clean. They do -not when they get trash and fuel gum in them or the O-rings are destroyed by ethanol or MTBE in th efuel or harsh 'injector cleaner' solvents. Also any fuel injector that is no longer on its original flow vs pressure curve will cause low or high fuel flow to that cylinder.

Theoretically, you CAN adjust each metering assembly to closely match the flow characteristics of each particular injector. Has to be done on a very expensive 'flow bench' and takes lots of time. Benefits are very marginal IF all thw injectors are within OEM specs. Since these injectors are cheap, (compared to electronic ones), its more cost effective to bench clean or buy new ones than try to adjust the fuel distributor.

Adjusting the fuel distributor is NOT a job for a DIY--even if you ARE highly skilled in other areas. Without the very precise,accurrate, and $$costly fuel flow test equipment, you have no possible way to adjust the fuel flow metering assemblies as required to achieve the balanced flows needed.

This is why everyone migrated to electronically controlled fuel injection--it simply was not possible to achieve the precisely identical fuel flows (fuel-air ratio)required for the 3-way oxidation catalyst systems to function properly.

I see your point.
Here are some remarks:
- The car had less than 100k miles in it when the timing chain (those cursed one-row chains) broke. The car was standing still for about 2.5 years at this guy I bought the car from. This obviously explains the sticky valve and the destroyed o-rings. The manifold gasket inside the distributor is in great condition - it is just the o-rings that do not bring it anymore. (nothing inside has wear marks either) - so I figured if I clean it - do not touch the flow control bolts (the allen bolts behind the allen bolts (as those o-rings seem to be intact)) but replace the rest of the seals then I should not modify any of the flow characteristics. I have found some places on the net that do offer a flow adjustment if you send in your fuel distributor.
I have a hard time buying a used one as it may have problems soon. I have a hard time buying a new and/or rebuilt one as I did not pay much more for the entire car . This was supposed to be a fun project - but now it is getting deep into my pockets. I measured the o-rings inside and now I will try to find fuel-resistant o-rings in those sizes.

If I understand you correctly, the only right way to adjust the fuel distributor is to adjust with its corresponding injectors - right?

Thanks!

Greg

Thanks all,

Greg

__________________
1983 560SL Megasquirted (originally 380SL)

My former Mercedes:
1985 300SD ~190k
1990 560SEL
2000 C220 CDI
1983 380SEC 102k dual-chain conversion
2000 C280 70k (sold)
1987 300DT (W124 - sold)
1972 220D (sold)
1971 220D (sold)

If the unit is not rusted inside, which would alter fuel delivery, I don't see any reason why you can't open it up and replace the o-rings. I know several people that have done this and they have been pleased with the results. Use acetone to clean all parts, and make sure you don't drop the plunger on the ground. Save your $$$. A rebuilt unit is probably close to $1000.00. Mechanics of yesteryear would fix things rather than replace. Buying a rebuilt unit means buying something that was fixed just enough to last through the warranty. Good luck.

You don't really need the flow bench to set up the CIS head. Most guys call this a "milking machine" because it looks like a cow miker. I have seen CIS cars set up run great with low emissions without any special tools other than the 3mm allen for adjusting fuel flow. True, each injector can be set up individually, but why bother? Try finding someone who has the tool and knows how to use it. You will spend quite a bit of money, for nothing. Being an engineer, you can do a better job than anyone else. It just takes patience. Someone once told me the mechanical injection pump on my 220SE was toast. The plungers were stuck. I took it apart and put it back together and the car runs great. I saved big $$$.