Here are some technical tips for the Wedge Family of cars:

Wheel bearings

Rear Suspension Pivot Pins

Adjusting the Bosch Fuel Injection

Wheel bearings:

Here are the Timken part numbers for 280i wheel bearings:

Front:
"Set8" for the inner front wheel bearing
"Set1" for the outer front wheel bearing

Rear:
Rear wheel bearings are SKF number GRW213.

All of these wheel bearings can be purchased from Motion Industries (formerly Berry Bearing), which is owned by the same holding company as NAPA/

Rear Suspension pivot pins:

The rear suspension consists of a semi-trailing arm that has a lateral (runs across the car) arm that mounts to the frame and to the upright. That is the bottom link. The top link is the half-shaft, which has U-joints in it, but no sliding splines like in the M-series half-shaft. There is a coil-over shock/spring unit also attached to the upright. But the front connection is what breaks. The front connection has a pin that is mounted in a rubber bushing on a boxed in section in the backbone part of the frame. This pin is a 14 mm diameter on one end and a 12 mm diameter on the other end. It has a step in the middle and the 14 mm part has some metal cut out for about a cm that makes it oval (like an oval race track actually -- with 2 short straightaways). That oval part slips into a large oval shaped plate that rests against the frame. The pin's 12 mm part goes through the frame and into a rubber bushing and has a bolt on the end. The pin / plate / bushing / washer / locking nut holds the pin to the frame. It can move (probably too much). Shims are put on the 14 mm part of the pin to set toe-in and the trailing arm slides over the 14 mm section of the pin and a locking nut with washer is put on and tightened to hold the semi-trailing arm on the pin.

When (not if) the pin breaks, it is because it is frozen up in torsion (twist). The problem is that unless the pin in the semi-trailing arm is kept lubricated, water and road gunk gets in and causes the pin to freeze up on the trailing arm. Once that happens it is only a short time until you hear a "plink" sound and the rear wheel is dragging against the rear wheelwell arch.

There doesn't appear to be a problem with the strength of the pin unless it freezes up. SO.... lubricate it once a year with anti-seize compound and there should be no problem.

Adjusting the Bosch Fuel Injection

One of the nice things about the 280i is that it has Bosch K-Jetronic fuel injection, which was an early computer-controled injection system. It uses continuous injection that has the volume of the fuel injected into the manifold by 6 injectors close to the intake valves controlled by a "closed loop" system, once the engine reaches operating temperature. There is an O2 sensor in the exhaust system that reads the amount of Oxygen in the exhaust. The computer reads that sensor and if it is too rich it opens a bypass valve (on the left front inner fender) to reduce the fuel pressure and return fuel to the tank. If the computer determines that mixture is too lean, it closes the bypass valve. It cycles many times a second and you can hear it humming as it does so. The fuel is continually returned to the left tank and run through the filter again, so the fuel is kept pertty clean. The fuel pump is behind the drivers' seat under the car. Since there are two, 7 gallon fuel tanks (one on each side), each tank drains to a "swirl tank" below the tanks that accumulates fuel and keeps a airless supply ready to be pumped by the fuel pump to the metering unit.

The computer is located above the passenger's legs in the passenger compartment in most 280is. A few 280is from around 1985 have the computer in the trunk behind the left fender trunk lining.

To run well, the computer must be plugged in, the O2 sensor must be hooked up and working (replace it every couple of years) and the bypass valve plugged in. If any of these things are not correct, the system will still run, but is in "limp home mode", which give awful fuel economy and fowls the plugs af ter a short time.

This system can be adjusted for mixture. Actually, it is rumored that the car can be leaned out to the point where it passes 1986 emission requirements without a converter, but it certainly shouldn't be driven that way!

You can adjust the mixture of the fuel by using a dwell meter. You need a long 3mm Allen Wrench also.

1. Hook up the dwell meter to the battey and the sensing lead to the "duty cycle" wire near the ignition coil It is blue and usually has a snap connector on the end to cover it. It should be labeled.
2. Set the meter to the 6 cylinder range
3. Run the car up to operating temperature
4. Insert the long 3 mm Allen wrench into the tube at the back of the metering unit. The tube is usually gold colored and may be plugged (but probably not, since these cars are old now). The tube is on the part of the metering unit that has injection tubing attached.
5. While the engine is running, gently turn the Allen wrench until the dwell meter reads about 30 to 32 degrees. Be careful and do not put pressure on the Allen wrench.
6. Rev the engine to 3000 repm and hold for 10 seconds or so. After it returns to Idle, readjust if it is not holding about 30 to 32 degrees.

That will set the mixture so it is at least close.

If you are still having problems, replace the O2 sensor first. If you have replaced the restrictive exhaust system, you can put an O2 sensor in either downtube and use just one.