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Old 11-17-2008, 08:27 AM
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vacuum leak or injectors? Or both...?

I run VERY rich. Black, wet smoke rich. Better once it gets warmed up, but still not great and, if I kick it down a gear, it comes with a black "puff"...

Further, occasionally when I first start cold (BTW, cold starts are easy) it sputters and coughs at under 500RPM. Once warmed, this does not become a problem again...

Vacuum gauge on the fuel economy is pegged left in P and N, but hovers at about 1/4 once in gear... Bought a vacuum gauge and tested by the brake booster--holding the gauge by hand--no perfect seal there--it read ~19.

Any ideas other than the mechanic's (which was to spend 10 hours of labor looking for the vacuum leak) would be appreciated.

I bought a bottle of techron to add to the fuel as well, with the thought that it may help clean the injectors if that is, indeed, the issue. Anyone have an opinion on that? Will the additive do more damage than good??

I'm still learning to feel my way around the car, so any ideas or advice are appreciated!


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Old 11-17-2008, 08:31 AM
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Location: Marysville, CA
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Welcome to the forum. First thing to know about getting help here is to give us some basic info about your vehicle: model, year, chassis.
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't
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Old 11-17-2008, 11:27 AM
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Join Date: Jan 2006
Location: Northeast Indiana
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Read the Techron bottle. It is basically a solvent which will become diluted in your fuel, I've NEVER had any fuel-injected vehicle respond to adding Chevron Techron to the fuel.

It does sour the oil however, which is why it is recommended that you change the oil after using it.

RedLine Oil makes a good quality detergent-based product, I believe it is called "complete fuel system cleaner" or something like that, which in my experience has mproved the spray pattern of fuel injectors.

However, it sounds like your problem is beyond simple cleaning of injectors, better to find the source first, and model/year information will help.

Gone to the dark side

- Jeff
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Old 11-17-2008, 11:34 AM
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Location: Charleston, SC
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Try unplugging the connnector to the cold start injector it may be dumping fuel all the time. Happended to me on a 300E once. I unplugged connector and car ran fine.
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Old 11-17-2008, 01:11 PM
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I'm sorry.
It's a 1983 380SL with about 97K on the clock...
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Old 11-17-2008, 01:18 PM
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Join Date: Sep 2008
Posts: 7
A bit more information...
The car was running fine (more or less), but with a slightly high idle. Shop replaced the Idle Control Valve (after, they said they took out the Idle Control Unit, tested a new one, saw no improvement, and replaced my original one...) SLIGHT improvement to the idle but within a week, serious other matters at hand. Car basically sputtered and coughed and depressing accelerator was met with little to no forward motion...!

Limped back to the shop (only a mile or so from home...) They replaced the fuel pump and filter (for FREE--wonder what they really did to my car under the hood!!) Car ran again, but now I have the aforementioned rich-running problem...

So, here I am now, with a beautiful car, spitting out less than beautiful smoke!

Ron in SC, where would I find the cold start injector?

Thanks all.
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Old 11-17-2008, 01:37 PM
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Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
The first thing you should do is find a new mechanic. Then ask the new mechanic to check system and control pressures for you. This should be about an hour's labor and is basic to a mixture problem.

Take a look at the vacuum line where it comes off the rear of the intake manifold by the firewall and follow it over to where it branches on the driver's side by the rear corner of the hood. IIRC, the line from the engine branches to:

- reserve tank under RF fender
- door locks (yellow)
- heat/ac (green)

Go buy some rubber fittings and a plastic "T". Try "T-ing" your vacuum gauge into the main line from the back of the intake manifold. Then unplug each of the lines above, and cap it on the vacuum side. See if the in-gear vacuum improves.

Also carefully inspect all the lines, fittings and rubber connectors for cracks loose connections.
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
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Old 11-17-2008, 03:42 PM
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I don't know if it's your problem, but I had a BMW about that year with the Bosch L-Jetronic, the fuel pressure regulator developed a pinhole in the diaphragm and was dumping fuel into the intake via the vacuum line.

Gone to the dark side

- Jeff
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Old 11-17-2008, 04:17 PM
Benz Mercedes's Avatar
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Join Date: Nov 2006
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A faulty Warm up regulator can cause these symptoms.


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