My plugs indicate that my car ( 74 450 SE) may be running rich.
Which way do you turn the bolts on the fuel injection
pressure regulators to lean it out a little.
I know that probably takes sophisticated diagnostic
equipment, but I was going to carefully count the
amount I turn the bolts so I can reset it to where they
are now if needed.

A pressure guage that reads 30psi should set you back 10$, plus the 5/16" plumbing to connect it. I prefer to tee mine into the cold start plumbing, since I can leave the gauge there and drive the car.

Of those two metal cans on the manifold plumbed into the gas lines, the one with three hoses is the pressure regulator. Loosen the screw to drop the pressure. DON'T do that w/o first hooking up the pressure guage. The other one (two fuel lines) is a vibration damper. I am not aware of it being adjustable.

Once you have the pressure right, AND your ignition system is working to spec (no, not simply "close enough"), you can working on getting it to idle right. There are exactly two adjustments, the big screw at the front for idle air and the thumb wheel on the brain box. Ideally, you want to do this with a tailpipe sniffer in place, you are looking for the lowest level of CO% emission while it idles at 800rpm. Make sure the electrical connector on the air cleaner is in place when doing the adjustment.

Most shops have the necessary hardware (in the US) to measure CO%.

-CTH

__________________
- cth350@gmail.com
http://www.111lakeside.com/

you don't want to adjust the pressire to leamn the mixture, on the fuel injection controller there is a wheel that you can turn to richen or lean the mixture, i don't recommend adjusting it with out the aid of an exhaust analizer connected.

I needed to measure CO on my '84 280SL.

At least in Northern Virginia, it is getting hard to find shops with a tailpipe analyzer. I bought a Gastester CO analyzer on eBay for about $175, and was unhappy with its results - it would constantly go out of calibration, so I was never sure of the reading that I was getting.

My next solution was to have a hole drilled and tapped in the header pipe for a Bosch single wire O2 sensor. The sensor is calibrated to produce .45 volts at the "perfect" air to fuel ratio of 14.7:1. Higher voltage is richer, lower is leaner. So you can get the engine good and hot and put your DMM between the sensor wire and ground and get a pretty accurate reading of your mixture.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe