Pull IP for repair?

[Ron]

Background: I'm still trying to sort problem at idle with my car.  It is a '66 230SL, 'had a R18 pump when purchased, and with rebuild last summer, I found and installed a proper R11 pump, purchased as a core.  The R11 was stuck when I purchased it, so it went to a west coast repair station, and was returned "cleaned and with new seals".  I'm pretty sure nothing else was done, as the oil in the governor was filthy, what was left of it.  It had no shims on the WRD or the BC, and a couple of poppet valves were stuck.

While the car ran ok, it hunted at idle, with about a 2 sec period.  Plugs were lily white.  I did hours of study on this web site, did the linkage tour, checked the dwell, timing, plugs, plug wires, but decided to start adjusting the shims on the BC.  That is, put some shims in.  At about 1.9mm, things were better, but the plugs were still white.  At 2.1 mm, plugs got a bit tan, but the engine was not as powerful as at 1.9mm.  

Today, I borrowed a SnapOn meter to measure CO.  The best I could do was the following, with 1.3mm shim:

RPM                 CO from BBB                 CO from meter

Idle                  4.5 to 1.0                   2.5 to 3.3, moving, with RPM change of 700 to 1000, 5 to 10 sec. period

1500                 4.0 to 1.0                   3.1

3000                 .3 to .2                       2.1 but varies up to 4.1 if idled then re-reved.

So I'm at a loss.  It seems much is not repeatable.  For example, I change shim to richer (or leaner), then start car.  Idle must be adjusted leaner (richer), with pump thumbscrew.  After about a minute, the engine will speed up and settle to new idle, requiring a new idle adjustment. I can cause it not to return to the set idle, by releasing the throttle very slowly.  It seems the IP has some internal friction the last degrees of travel for the linkage lever.  I did put a bit stiffer throttle spring on the butterfly, but that does not seem to help give a consistent idle. 

I have removed all shims from BC and still not at proper CO for 3,000 (only down to 2.0) and idle is horrible.

Should I pull the pump?  Who to send it to, where it will be carefully checked?

Thanks.  

Ron

PS  And thanks for all the help from this group of people.  I would have long ago pushed this car off a nearby cliff into the Pacific if it were not for you folks.

[stickandrudderman]

One of the first things I do when asked to investigate a car that won't respond well to the usual checks & adjustments is insist that the pump goes off to be calibrated. It's such a fundamental requirement for even running that I'm wasting my customer's money by doing anything else.

[Benz Dr.]

I would agree with you Collin.

In this case the pump is set too lean. Once the plugs started to turn tan or darker you were getting into the proper range. At that point, you propbably could add a couple of degrees of ignition timing, something you can't have when running too lean.


Having said all of that, maybe you need a proper rebuild.