Running rich

[Loungestx]

Hi guys.
First post. I have had my 71. 280sl for many years and it has always had a rich running issue. I put in hotter plugs as a temporary fix to the plugs fouling but it is a issue. I am very mechanically able but the only thing I have ever worked on with mechanical injection in the past is diesels. I wonder if the pump is out of adjustment but I heard you can only adjust it while not running and that seems impossible unless you have done it before and know some shortcuts. Or possibly a bad relay or leaky cold start? Anyone know of a typical issue to start with? Also looking for a mechanic that knows these well,about 2 hours north of manhattan. Near Woodstock NY.
Thanks in advance.
Don

[kampala]

Don,

Welcome to forum. 

There are many reasons why these cars can run rich.  Start with the easy stuff.  I will allow those with more experience to provide further details, but here are a couple of things to check right away.

The CSV (cold start) as you mentioned is a big one.  These do leak sometimes.  You can read how to test in the tech manual and by running a search on the site.  You will find the details. Or you can disconnect the fuel line to it and plug the line temporarily.  This will remove the CSV from the equation.  Removing the electrical on the CSV will not stop it from leaking if it leaks.  The tech manual also shows how to repair once you validate if it's not working correctly.

Second, find the Warm Running Device (WRD). This is located on the injection pump.  When cold, you should hear air being sucked in from the small can filter on the WRD. As it warms, the air should stop being sucked in.  If Air continues to being sucked in, the WRD is stuck. This means it continues to keep the mixture rich for a cold start even after the engine is warm.  Again, Search WRD and look for it in the tech manual -- you will find more than you want to know. 

You can start with these two major culprits as they are easy to check.   Others with experience may offer other items to go after but these should get you started.  Good luck and let us know how it goes.

[ja17]

You will also need to check the engine linkages. If they are set up wrong you will never get the injection working correctly. "The Linkage Tour" will guide you through the process.  Next learn about the split linkage test so you can understand when the engine is running rich (hot, cold, low rpms, high rpms etc.).  We can help you through these steps. There is plenty of info to read about this on this site  to read about this also.

[jorge espinoza]

I just had the same issue as my mechanic was installing the 123 ignition . He was having major issues with the car running right . His diagnosis was a leaking CSV . I went to the shop and he showed me that even with the Valve disconnected it was still dripping fuel causing a big headache on the  proper  running of the engine .

[Tyler S]

I think a few have a hard time understanding why the CSV can leak even with it disconnected electrically. There are 2 systems incorporated into the housing. The electrical solenoid and the mechanical needle, seat and spring.
Think of it as your garage door. The garage door opener is the electrical solenoid, and the garage door is the mechanical valve.
You can close your garage door onto a broom handle (piece of dirt) and a gap will exist. You can then unplug your garage door opener and that gap will still exist.
The closing of the valve is determined by the mechanical spring, needle and seat. Not the electrical solenoid. It just opens the valve.
Tyler

[Kayvan]

Per the Classic Center, timing/dwell/points/CSV/WRD need to be checked at each service (12mos)...

These cars are not "set it & forget it"

I think many dont want to touch things and end up living with cars that naturally cycle off optimal settings

[ja17]

Actually, I believe that the original tuning  service interval, as per the owner's service book, was 12,000 miles.

[Dave H]

Watch Kent Bergsma describe why these engines run rich, very interesting.

https://www.youtube.com/watch?v=PLedjKWbU5w

https://www.youtube.com/watch?v=nmkiBz65Wjs