PeachParts Mercedes-Benz Forum - Ideas as to huge MPG drop since overheating?

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Fuel pressures are dead on....

http://w124-zone.com/downloads/photo...2010/fpt-4.jpg
http://w124-zone.com/downloads/photo...2010/fpt-5.jpg

I hooked up my vacuum gauges for the heck of it....Anybody know the idle specs that I should be looking for at idle? Do mine look about right?

2 more tests done

1) Have 13.9v at the O2 sensor white wire.
QUESTION -- Only ONE of the wires showed voltage. The other did not give me a reading. Should BOTH white heater wires give voltage?

2) Probed EHA and it gave me a fluctuating reading between 8-10mv. What does this indicate?

Somebody recommended putting a sniffer on the exhaust. I have found a local shop that may be able to get a CO2 machine on the car for me...

Will that help me in any way figure anything out?

I think I will unscrew the O2 sensor and just physically feel if it heats up instead of guessing regarding the voltage on the wires.

Want to keep this thread together for future searchers.

My o2 sensor readings. Does it show anything? I can't seem to make heads or tails of it.

http://www.youtube.com/watch?v=QAmRXaGyW0w

bump...

Any other ideas?
I'm gonna swap in a spare fuel distributor I have cleaned up and see what happens.

What are the chances the injector tips could have gotten damaged during the overheating incident?

Anything is possible. If you can take them out have a look at them. Have them pop tested to make sure they open at the right pressure. Id also suggest looking at the exhaust system. If you have cat converters they may be partially obstructed. High egt's and engine heat can melt them a little and cause your engine to work a little harder

Alright dude, Lets try this systematically:

1) Federal or Cali Car?
2) Duty Cycle Read out (x11) at op temp idle and 2500rpm?
3) If constant %, then we got a fault.
4) If not constant %, we're gonna test all the CIS-E mixture related devices.
This is from a 560SEL, but most of the same stuff is in the 124 m103. The m103 126 didnt have a nice diagram like this...

http://i.imgur.com/MmPfTl.jpg

Make sure each component is working within normal parameters, then make sure the CIS-E computer is getting the data.

Wow, thanks for posting the flowchart! Now I have to figure out where the heck the EGR temp sensor and altitude sensor are on my 126 :)

O2 sensor and mixture are responding normally....

45-55% duty cycle, O2 sensor 0.1v-0.9v. If I try to lean out the mixture, the engine becomes very choppy.

Brand new EHA and O2 sensor...all ignition components are new. No vac leaks. New fuel filter. That is why I believe it could be fuel related.

California, but as an 87 just has the O2 sensor light.

Read an interesting post by Stevefbl....
http://www.peachparts.com/shopforum/tech-help/116704-fuel-distributor-test-accurate.html

Quote:

Originally Posted by stevebfl (Post 830043)

Actually unless you are below 59 deg the cold start valve doesn't work. This means that the combined enrichment of starting and starting cold allows fuel to flow at cranking speeds. The amount of fuel is that which runs the car 20 miles to the gallon or about twenty minutes to a gallon at road speed.

If you think about that, you will see that the amount of fuel used in each stroke is quite small. It won't spurt. Even if the airflow plate is held way down the flow will be small.

The mechanism I use for basic setting of mixture after the fuel distributer has been replaced is to bypass the fuel pump relay and adjut the mixture till fuel rises in the threads on a removed fuel line. Once flow is noticed the mixture is adjusted lean till it doesn't flow. Key on engine not spinning there should be no flow. Push the plate down and there should be even flow from all six chambers.

Might give it a shot when I swap distributors tomorrow. Should be interesting!
May also try a shot at fuel quantity measurement...Might be worth just pulling the injectors.

I'll give a shot at cleaning them first too. A visual inspection may give an idea to if the overheating caused any damage....

Check the fuel pressure regulator. When it starts to leak it will vent into the intake via a vacuum line.

Quote:

Originally Posted by hstuehmeyer2000 (Post 2643587)

Check the fuel pressure regulator. When it starts to leak it will vent into the intake via a vacuum line.

Regulator is good, no fuel going through vacuum line.

I received a new set of injectors + seals today. Gonna get them in tomorrow and fingers crossed that resolves it. I opted to check out my current insulators first before spending an unnecessary $35 on those suckers.

In any case, the car is long term so probably a good move anyway.

Did the injectors fix it?

Earlier on someone had underhood fumes issue diagnosed to a leaky EHA.
wonder if you had tell-tale smell of fumes .
mak

Finished up the injectors....
No difference unfortunately. The mixture went way off, so something changed for the better I hope.

It's just so confusing why this happened after the running hot incidents...
I keep wondering if compression or leakdown was affected, but I'm not burning any oil or anything.

Fuel filter is about 10k old...

Any thoughts on next?