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  #16  
Old 12-30-2005, 09:34 AM
Ta ra ra boom de ay
 
Join Date: Jun 2004
Location: Pittsburgh
Posts: 1,915
How far do you drive on average per trip?

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html
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  #17  
Old 12-30-2005, 05:30 PM
'90 300se, '95 c280
 
Join Date: Oct 2005
Location: Honolulu, Hawaii
Posts: 112
Hi Marty,

I average a whopping 7 miles from home to work , roughly 6 miles of which are on a highway with low congestion and around 60mph. Could the short distance have something to do with it? I'm pretty sure that there are some things that aren't being brought up to a high enough temperature, so I plan to take the occasional "scenic route" to get everything nice and hot (the car, that is). Thanks for your input!
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  #18  
Old 12-30-2005, 05:42 PM
Ta ra ra boom de ay
 
Join Date: Jun 2004
Location: Pittsburgh
Posts: 1,915
7 miles should be enough.
Is it getting up to full opperating temp's what does the gage read halfway through your trip? (above80?)
It seems unlikley in Hawaii that running cold would be a problem... but you never know.

Also have you checked the water temp sensor (top rear of the valve cover) for propper resistance range?
__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html
Reply With Quote
  #19  
Old 12-30-2005, 06:43 PM
'90 300se, '95 c280
 
Join Date: Oct 2005
Location: Honolulu, Hawaii
Posts: 112
Hi Marty,

Yes, the temperature goes above 80 and is usually closer to the next mark (90?). Ambient temperature here goes down to bone-chilling upper 60's at night!

I haven't checked the water temp sensor yet, but will do some searches on it and test it out with my meter, probably over the weekend. Thanks again for your help!
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  #20  
Old 01-01-2006, 01:00 AM
'90 300se, '95 c280
 
Join Date: Oct 2005
Location: Honolulu, Hawaii
Posts: 112
I got around to checking the water temperature sensor today with an analog meter so my results are not very accurate, but I'm pretty confident that the sensor is a goner based on my results. The sensor on my car is the (thankfully cheaper) 4-pin CIS type.

I checked the resistance on opposing pins on the temp sensor. With the engine "cold" and ambient temperature around 26 degrees centigrade, I got a reading of 4KOhms. With the water temperature gauge on the dash reading roughly 80 degrees centigrade, I got a reading of roughly 1.7KOhms.

If I've read past posts correctly, the fuel management system is basically being misled and is assuming that the car is running at roughly 30 degrees centigrade when it is actually around 80. I don't know at what temperature the system decides to stop running rich, but 30 is pretty cold for an engine so I think that might be my problem. Could someone please confirm that the water temp sensor used on my car should give readings as follows (copy/pasted from one of Marty's old posts):

Degrees KOhm
20...........................2.5
30...........................1.7
40...........................1.18
50...........................0.84
60...........................0.60
70...........................0.435
80...........................0.325
90...........................0.247
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  #21  
Old 01-01-2006, 01:17 AM
Ta ra ra boom de ay
 
Join Date: Jun 2004
Location: Pittsburgh
Posts: 1,915
I'm 99.9% sure you've got it. :-)
__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html
Reply With Quote
  #22  
Old 01-04-2006, 01:50 AM
'90 300se, '95 c280
 
Join Date: Oct 2005
Location: Honolulu, Hawaii
Posts: 112
Well, I picked up the sensor at the local MB shop today and checked out the resistance on the pins before removing the old unit. It turns out that they were the same and that my analog meter was at fault. I got my digital meter back from my buddy who was borrowing it, and found that the old sensor is within specs.

I'm going to take the sensor back tomorrow, but am not sure what else could be causing the poor fuel economy. I think the next logical step would be to check the EHA, fuel injectors for leakage, then the fuel pressure regulator and distributor. Is that "all" that can go wrong?
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  #23  
Old 01-09-2006, 07:36 AM
'90 300se, '95 c280
 
Join Date: Oct 2005
Location: Honolulu, Hawaii
Posts: 112
Just in case this might be useful to future searchers, the problem apparently turned out to be my OVP. I had previously removed it and found no rattling, so I assumed that it was ok. This time around, I opened it up and resoldered the few connections in there "just in case." Anyway, I took it around the island on Saturday and found that I got around 90 miles out of the tank while going from the 3/4 marker to the 1/2 full mark. The car still runs richer at 2500rpm when testing the duty cycle, but I can live with that for now.

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