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· Registered
1990 Mercedes 560SEL
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593 Posts
If your car does not accelerate very well, then it could be a bad fuel pressure regulator. But don't just rely on this symptom alone. This symptom can also occur if you have bad fuel pumps, bad timing, broken O2 sensor. You will have to do some tests to determine, wheter the fuel pressure regulator is bad.
 

· Moderator
1987 & 1991 C126
Joined
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6,923 Posts
Hey Louie,

Please post the symptoms which you are questioning.. IE: The car does such & such when I do this... etc.

You may strike paydirt early on..

Good Luck.. & Cheers.

M
 

· Registered
1986 560 SEC
Joined
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67 Posts
My symptoms were huge, embarrassing plumes of black, chunky smoke (especially when cold and when accelerating) and even worse gas mileage than normal. I'd already replaced the O2 sensor, plugs, plug wires, cap and rotor, and other things I'm not remembering. It still smokes a little when starting (more gray than black and I'm taking a break from troubleshooting for a while), but I averaged around 20 mpg on a road trip down I-5 after replacing the regulator. Usually I get around 15-16 driving around town, but got as low as 10 with the bad fuel pressure regulator. We do as many repairs as possible ourselves, but went to a German car specialist to test why all the black smoke. If I'm remembering correctly, it was spraying about 40 PSI more than it should have been. After replacing the regulator, I replaced the O2 sensor and plugs again because they were really gunked up from all the carbon going through the system. I'm guessing that the cats are probably full of crap as well, all the more reason for my son to build me a new exhaust system.

By the way, new plug wires made a big difference in the acceleration and overall smoothness when running.
 

· Registered
Mercedes 420 SEL 87'
Joined
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163 Posts
Discussion Starter · #5 ·
its cutting out mostly on acceleration most of the time just after filling up with fuel but also cuts out during the mid range sometimes. Replaced fuel pumps, accumulator, fuel filter, fuel pump relay, idle control valve, O2 sensor, plugs, wires, Distributor cap/rotor. Previous owner had the timing, guides and tensioners done not long ago. All i can think of now is maybe the AFM, fuel distributor or fuel pressure regulator?
 

· CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
Joined
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50,641 Posts
MBL87560SEC said:
Hey Louie,

Please post the symptoms which you are questioning.. IE: The car does such & such when I do this... etc.

You may strike paydirt early on..

Good Luck.. & Cheers.

M
Hi Malcolm, good to see you in the neighborhood.
BTW, the offer to find and re instate your DIY post still stands.
Cheers
 
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