A problem with my 72 280 again. - Mercedes-Benz Forum

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post #1 of 4 (permalink) Old 08-01-2008, 11:40 AM Thread Starter
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A problem with my 72 280 again.

My 72 280 sel 4.5L auto. has been running rich. Recent tune up and everything has been done. My mechanic leaned out the fuel ratio for me but suggested that I need the two fuel pressure regulators which are $100 dollars each. These also need to to be installed and adjusted (labor?). Is this what is wrong? Is that all that needs to be done? Any input would be greatly appreciated.............................I get better advice about my automobile from this forum than I do from my mechanic or anyone else around here.....thanks
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post #2 of 4 (permalink) Old 08-01-2008, 02:58 PM
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Vehicle: 2004 W220 (S430) ; 2001 R129 (SL500) Sport
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Have you googled to see if there is a "Mercedes W108" forum somewhere? It's a shame there isn't one on this site, but I guess they are relatively uncommon. I've been nosing around thinking about buying another one myself, and there is a lot of stuff on the web about the car.

Also, I'd get hold of a repair manual for your car ASAP. I don't even know if the W108 has fuel pressure regulators, much less two of them. If you have a repair manual, you'll know what they are, where they are, and whether you can put them in yourself.

It sounds like you're getting nibbled to death by ducks. If I could replace any part on my W220 for $100, I'd be thrilled, but yours is a lot simpler. The regulators are probably mechanical, and there may be one for each cylinder bank. I wouldn't think there would be much labor--bolt off bolt on, fuel line in fuel line out.

"Don't pick a fight with an old man. If he is too old to fight, he'll just kill you."--John Steinbeck
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post #3 of 4 (permalink) Old 08-01-2008, 09:55 PM
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I can help

I just stumbled upon this subject.
And can help.
I have never had to replace the fuel regulators ever.
If leak, replace, if no leak, adjust per spec. Lifetime parts.
Check fuel pressure after replacing fuel filter.
Put W9DC plugs in check cylinder compression pressure.
If it passes and runs fine except fuel richness, take an Allen wrench to the MAP sensor (pop off the black (do not touch) cap) and crank it out (unscrew) 1/8 turn per run.
After turning map sensor idle may change too.
You will gradually lean out the overall fuel sensing system.
We took a 4.5 on a 1,500 mile run and gained mileage
from a rich 11.5mpg to a 16.4mpg and it has run perfect for 3 yrs since.
Also the ATF in the fuel tank at Qt / tank ratio was performed on this same run.

Of course, there are a few more little things which will affect the richness / overall running.
Superb motors.

Brian O
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post #4 of 4 (permalink) Old 08-02-2008, 10:08 AM Thread Starter
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Thanks for the input. A mechanic that has been working on my car said that the regulators needed to be replaced. I thought that they only needed to be adjusted too.
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