FIP: BC vs WRD ( Fuel Injection Pump )

[awolff280sl]

There is a good amount of info on this site about how shimming the Ward Running Device (WRD) affects fuel delivery at the fuel injection pump. There is also info on how shims under the barometric compensator affect fuel delivery as well. It seems to be the general concensus that shimming or unshimming the WRD is the preferred(?) way to enrichen or lean the mixture at all RPMs.
I've been intermittently working on my CO% and checking the color of my plugs. I came accross an old article by Frank Mallory and Tom Sheppard entitled "Care & Feeding of Mechanical Injection Systems". They discuss using the shims under the BC to make the full range adjustment, and make no mention of the WRD. (They assume that the BC is no longer working, which I guess is true in many of our cars.)
My question is this: what is the relationship between the BC and WRD in regard to mixture---in orther words, do shims under the WRD (which enrichen the mixture) prevent the BC from leaning the mixture, and vice versa? For me, it's quicker to use the BC rather than the WRD when shimming.       

[230slhouston]

Jeff,
I am not an expert on this but can share my experience. My car was running extremely rich, when I did the richness test, it would go over 5000RPM with the linkages disconnected and air opened. I could not even set the idle correctly. Through information on the board on the WRD and BC, I removed the shims from the WRD first to no avail. The only way I could get the richness correct was adding a shim under the BC, actually a copper washer. This allowed me to set the idle within specs as well. The only minor glitch is when I start my car, I cannot give it full throttle, it tends to cuts off. If I let it warm up for a minute, no problems. Acceleration is not a problem and cruising at 80MPH is no stretch.

I have not done any CO test but my gas mileage is 16 to 17 MPG which is acceptable to me considering the age of the car.

Cheers,
Maistran

[paults1]

What is the BC?

[glenn]

Barometric compensator

[ja17]

Hello,

Adjustment at the BC is a lot more radical. A slight amount make a big difference.
Adjustment at the WRD is a little more controlable.  Add shims to lean at the BC. Remove shims to lean at the WRD.

Sounds like Maistan's car was very rich and the radical adjustment worked out.


The other alternative is adjusting the rack screw. It also adjusts all speed ranges at the same time.   Accessed through  a plug on the back of the IP.

Paul,
The WRC and the BC along with other inputs all interact together through a series of springs, levers and pivots inside the pump. It is the combination of inputs from the WRC, BC, centrifugal flyweights (engine rpm), and linkage position which combine and interact to regulate the fuel mixture.

[awolff280sl]

Joe,
Sorry, but now I'm really confused. According to Frank Mallory's article, he REMOVED shims under the BC (Barometric Compensator) to lean the mixture. (He goes into an explanation about how higher altitudes are supposed to make the pin in the BC protrude further which leans the mixture for rarefied air. He contends that the PES pumps tend to run rich over time with the BC not working. In fact, he found it common to have to remove all the shims including the thick one to get a good mixture!) He does add warnings about creating too lean of a mixture.
In my car, I started off a few months ago with CO at about 6% at an 800rpm idle and my plugs were black. There was one shim under my WRD that I removed, but this really had no noteable effect. There were 3 shims under my BC with a total thickness of 2.4mm. I exchanged these shims for a combination of .1mm and .2mm shims also totalling 2.4mm so that I could make gradual small adjustsments over time. I have gradually removed shims in .1mm increments and over time my CO has gone down to 4.5% and my plugs have lightened up. In fact, the plugs are now somewhat whitish and I'm thinking about adding back another .1 or .2mm. I'll have to watch this.
Joe, am I in left field?   

[ja17]

You may be correct Andy, I may be backward on my BC shimming! I very seldomeuse the BC shim adjustment.  In may be the rack screw which I recall as being opposit the idle mixture thmb screw!

Thanks,

Joe

[Dash808]

Are there pics anywhere of the shims under the WRD & BC?