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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,267
I have one and I was told the 6 metering slits in the steel cylinder the control plunger is inside of are CNC enlarged. That lets more fuel through to the top side of the differential valves for any given throttle position a little above idle speed.

The lambda frequency or pulse valve is also removed and the banjo bolt that connected it to the lower side of the differential valve chambers gets a threaded plug. That fitting is just to the right of the large flare fitting fuel inlet line. The black cast iron euro, rest of world, and pre 1980 USA fuel heads do no have that threaded port.
The other end of the pulse valve was banjo bolted in tandem with the return line from the warm up/control pressure regulator and when the pulse valve is removed that port gets a shorter banjo bolt so only the return line from the WUR is connected to that return line port.

Lastly there are 3mm spring tension adjusters under the 6 - 4mm button head plugs on the top side of the fuel head next to the fuel injector line banjo bolts. These 3mm adjusters adjust the spring tension on the top side of the differential pressure valves.
They act as small fuel pressure regulators, one for each fuel injector so you can fine tune the amount of fuel going to each injector. Turning the 3mm screw clockwise increases the spring tension on the top side of that valve and that lets a little more fuel flow through that differential valve and on to the fuel injector.

The modified fuel heads have a dab of green or brown paint on each of the 6 - 4mm button head plugs showing that that 3mm differential valve flow adjustment under it has been changed or checked.

It's impossible to figure out how the CIS fuel heads work without seeing cross sectional diagrams showing all the internal passageways, valves, metering slits, and flow restrictors with arrows showing fuel flow direction.
Old 04-18-2009, 08:52 AM
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