348 miles to a tankful of diesel... - Page 4 - PeachParts Mercedes-Benz Forum

suginami · #46 03-21-2004, 01:52 PM

I find the idiot lights are way off.

I think my owner's manual says that when the idiot light comes on, you should have 2 gallons left.

When I fill up when the light comes on, there is still 4-5 gallons in the tank.

84300DT · #47 03-21-2004, 08:17 PM

i've had mine stuck on 'R' for what seems like an eternity and not had the light go on.

psdsteve · #48 03-22-2004, 12:00 AM

I've had mine come on twice in the last month and it took 16.5 and 17 gallons respectivly. My OM says it's a 20 gallon tank so mine seems to be pretty close.

Stephen

Plantman · #49 03-22-2004, 07:11 AM

Ok the results are in.

I rode the idiot light for about 40 miles to finish with a grand total of 438 before I filled up. Didn't want to risk running out and using my spar veggie oil needlessly.

Filled up with 21 gallons.

THe end result is with new inj. and timing adjustment, I got another 100 miles and my average went up to appox 22mpg for mostly city driving.

bigchingan1 · #50 03-22-2004, 10:09 AM

from what I understand, the gov mandated changes in diesel fuel to make it cleaner some years back (late 80s early 90s?). One of the additives used made it more "sticky" and harder for the old style w126 gauges (and I imagine any other older gauge) to read acurately

#51 03-22-2004, 01:46 PM

My fuel gauge seems to work just fine. The owner's manual says that the idiot light comes on when there are 3.8 gallons of diesel left in the tank. The idiot light comes on when the gauge touches the "R" mark. Last time I filled up, I put 21 gallons in, and the idiot light had just come on... 430 miles on that tank.

wolf_walker · #52 03-22-2004, 03:54 PM

Seen the same things with my fuel gauge, w123. I pulled the sending unit, cleaned it, verified it's readings as all the FSM gives is a full ohm reading, an empty ohm reading, and tells you the light should be on when it's empty.

Previously in stock configuration, my idiot light came on, and the gauge needle bottemed out, when it was just on the R. I had the sender out and recalibrated mine by moveing the needle such that full is dead on the thick line, and the light on/empty is at the lower side of the R. Good as it's going to get for twenty year old stuff. My wireing has little to know resistance in it, the sender is within an ohm of spec, I don't know what else to do with it as I can't find any specs to check the gauge with.

As a note, when the light is on solidly, the gauge will not go any further down as the sender bottems out to make the light circuit, so don't expect the gauge to drop after the light is sollidly lit.
W123 and probibly w126 info there, can't speak for later models.

And my light comes on when I have roughly five gallons left, but I don't have the guts to drive the poor thing dry, so I almost always put in 15-16 gallons from the 21 or so it's suposed to have, around 400 miles or so.

driad_98 · #53 03-22-2004, 05:01 PM

Where on the instrument cluster is the low fuel light? I ran dry not long ago and didn't see a warning light. '80 300D. Thanks.

Ash

84300DT · #54 03-22-2004, 06:08 PM

Quote:

Originally posted by driad_98
Where on the instrument cluster is the low fuel light? I ran dry not long ago and didn't see a warning light. '80 300D. Thanks.

Ash

at least on an '84 the light is right near the fuel gauge.
when you turn the key on to glow, it should light up as a 'test' that it works.

agree it's not a good idea to run the tank low. i always chicken out when the trip odometer goes over 400 mi.

but then again i don't usually carry any spare fuel. never had to call mercedes roadside assistance either... yet...

turbodiesel · #55 03-22-2004, 06:37 PM

I ran the 300SDL out of fuel on I-78 once.. I knew it was very low and I was pushing the limits. Called MB roadside assistance, they came out with 3 gallons of diesel and I was on my way in less than an hour. Next day I changed both fuel filters.

wolf_walker · #56 03-22-2004, 07:55 PM

Quote:

Originally posted by driad_98
Where on the instrument cluster is the low fuel light? I ran dry not long ago and didn't see a warning light. '80 300D. Thanks.

Ash

I'm not positive but I want to say the 80 model does NOT have the self test function in that the low fuel light comes on when you have the key in the glow position. I could be wrong though, but I read something about this and it starting in 82.. Anybody remember?

The light is a small ornage triangle to the above left of the fuel gauge, you can see it if you look close even if it's on lit up.

CSchmidt · #57 03-22-2004, 09:16 PM

Folks,

I just filled up - pretty empty. 22 gallons, 550 miles. 75% highway at around 70, 25% stop and slow on the highway. The temps in NC have been moderate, 40's-70's, no A/C and no real cold starts.

I was a bit surprized at how empty it was. My reserve light just came on 10 miles before I filled up. I had gone to reserve before and only been able to add about 20+/- gallons. This particular fillup pump tips the car slightly to the driver's side, so it must eliminate all air gaps. The gage was as full as I've ever seen it as well. I guess I won't push reserver too far!

Chuck

86560SEL · #58 03-22-2004, 10:26 PM

You think that is bad? I ONLY get about 200 miles per tank in my 1992 Buick Park Avenue, with a 3800 V6. Despite it being a large car by today's standards, it should do a lot better than this- despite that I run often at half or 3/4 throttle when accelerating from a stop when I am typically running a few minutes late for work.

I remember when I got it- I at least got about 350 miles per tank and even that seems low. I think it has about an 18 gallon tank. Perhaps it is due for a major tune-up, despite the fact that it still runs great. Even my 1990 Lexus LS400 (V8) seems to do much better than this. I think that it has about a 22 gallon tank. I can get anywhere between 300-450 per tank in that car, depending upon city/highway driving and how fast I run it. 300 if stop and go city driving and around 400 if mixed highway-city. Also- being in eastern Tennessee- there are some hills around- which effects economy. I have never had this car on a "highway only" tank of fuel, as I have never taken it on a trip yet. I may get 450-500 if I did that, if the roads were flat.
The LOW MPG of the Buick is one reason I am selling it and buying a diesel 300SD Mercedes. I still want a large car, but with good economy.

About how many miles per tank are the owners of the 81-85 300SD getting?

Plantman · #59 03-23-2004, 07:38 AM

If you read some of the earlier posts, one member reported some 500 plus miles per tank on an SD.

My car on the hwy will get between 600-650 miles per tank.

psdsteve · #60 03-23-2004, 11:36 AM

86560SEL

About 450 - 500 miles per tank mostly highway miles. Reading the threads there is quite a bit of variability. I'm pretty easy on the throttle.

Stephen