My 1973 280se 4.5 is running rich. Only had it a couple of months Is their something I can do to clean the injectors and check for vacuum leaks. the plugs seem to be dark dry charcoal color.
any ideas.

If you don't want to actually pull injectors to soak them in carb cleaner, then just run a bottle of Techron in the next 2 consecutive tanks. Otherwise, if you eliminate vacuum leaks, you can turn your MAP screw with a 4mm allen wrench about 1/4 turn clockwise and see if it helps. The MAP sensor is on the firewall behind the engine.

__________________
Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

Make sure you have good gas in the tank! A high proportion of old dead gas will cause very poor combustion, so it looks like it's running rich -- uses tons of fuel, too, since you don't produce much power. Run it nearly dry, add a bottle of Techron or Redline, and fill it up with nice clean premium and it will run much better.

Look for vac leaks two ways -- with a hand vac pump by attaching the vac line after you remove it from the manifold or with a can of carb cleaner -- spray on suspected leakage area, and if the idle changes, you have a vac leak.

Places to check are the door lock line (yellow plastic, goes into the firewall by the brake booster), large vac line to the MAP -- it's usually rock hard and leaking, the seals around the injectors, the seals between the upper and lower intake manifold halves, and the brake booster and transmission modulator.

I'd also check the wires to the air temp sensor in the air filter horn -- these get a lot of flex due to their rather exposed position, and if they are bad, the ECU will run the engine very rich, often to the point of blowing black smoke. Check the sensor, too, it must have some resistance. A short, or worse, an open sensor will dump the fuel to it.

A bad pressure regulator will do this too, as the amout of fuel injected is a funtion of pressure and time open. Pressure must be 28.2 psi.

And, sadly, a bad anaeriod bellows in the MAP will cause very rich running. No way to detect this except by replacing it with a good one, an expensive experiment.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks guys, I will check those problems this weekend.
should I put 87 89 92 octane fuel which one on regular basis.

73 280se 4.5

Boy, you HAVE to run 92 in that car -- vintage MBs do not run on anything less (and it's not a "preference", it's a requirement as I understand it). My car runs like doo doo on anything less than 92 and that's pretty much standard from what I gather from this forum.

Catrinus
73 280C

Yup. If you still have your owner's manual, I believe it says 91 actually. But most of us, being aggressive, set the timing a little more advanced, thus need a little higher than that. If you run 89 or 87, you WILL kill your engine. Might as well run it with rubbing alcohol! Figuring for age which has added a bit of carbon (thus raising compression), you should use 92 or 93. If you have less than that in it now, DRAIN IT OUT and use it in your lawnmower or something! Put some 93 in that bad boy and add octane boost!

__________________
Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

Premium only, at least 93 octane! Mine rattles some on that.

It runs beautifully on 89 octane, have even better performance, but knocks terribly hot in traffic with the factory timing spec...

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!