So ;

Remove the sender, connect it and tip it back and forth ~ the gauge should follow and the low fuel lamp come on right about when the needle reaches the 'R' .

This should tell you if the sender or gauge or wiring is bad .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

85 300d turbo diesel. fuel gauge was working. I replaced multi purpose relay & gauge quit working. Switch relay back to original relay & gauge still not working. Could the relay cause gauge to stop working like that? Does anyone have electrical diagram for this car?

Begin by testing the fuses in the fuse box with a test light not a meter .

If you look at them and says 'they all look fine to me' stop, you're never going to fix it unless you do the actual work those crazy Mechanics want $50 / hour to do .

IMO, I'd automatically replace any silver or gray colored strip fuses because they're essentially worthless due to age .

It takes time to find the correct copper strip fuses but they're out there .

You shouldn't need a wiring diagram .

Yes, I have the factory diagrams but they're HUGE and are circuit diagrams, not overly helpful in figuring out what's what on the actual car .

I have no idea how to scan these and will soon be selling off or throwing out my large collection of factory shop manuals, I only need a few to cover my later production cars .

No one wants to buy them any where at any price and no, I'm not going to give then away for $20 each when I paid hundreds after searching for years to get them .

If there's any technical book store in the L.A. basin area , tell me and I'll sell them as one big lot along with many other brands manuals part & service, owner's booklets etc. but NO DIRECT SALES .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Found this thread and working on similar problem. Filled up last week and the gauge stopped at half. As I've been driving the gauge falls as if the half mark is the max mark if that makes sense. I short the level indicator pin to ground and it only goes to half. Since the gauge is moving it makes me think the sender is working but something is up with the gauge in the cluster. Any ideas? Thanks in advance.

WELCOME ADAM !

Read post # 31 and do that to test .

You'll need a #2 Phillips screw driver and a 46MM socket .

Or, use the biggest pair of Water Pump Pliers you can find .

I prefer to use the correct socket but the sender isn't tightly fixed .

It's underneath the first aid kit .

No need to $pend $ at the shop for this .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thanks for the welcome. I've been a long time lurker here and found a lot of good information.



I'll give the sender / float a look see and a test this weekend and see what that shows. i just found it a bit odd that when I pulled the connector off the sender and grounded the pin for the gauge it jumped to half, not full. We'll see what the weekend brings.


Thanks again

__________________
Central IL
1977 450SL - Orange Julius

1982 300D - Blue Steel

2014 E350 Coupe
1992 Ford Ranger

Okay ;

Let us know how it works out .

I have a spare sender that works but the needle flickers below 1/3 tank ~ it's always accurate near R though .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Pulled the sender, cleaned it up. There wasn't much to clean, just a thin black film. Pushing the float by hand the gauge moved along with it, but not terribly accurately. Float at the top of the sender put the needle between 3/4ths and full. Float about a quarter of the way up from the bottom the needle was at the R hash mark. Float at bottom turned on the reserve light and the needle was pretty far below the R (The Seinfeld episode where Kramer is seeing how far he can go below E on a test drive came to mind) Not perfect, but now that I know the quirk I can manage it. I still find it strange though that when i jump the ground pin and the needle pin on the plug it only brings the needle to the 1/2 mark on the gauge, did it again today. oh well. On to the lumpy cold idle.....


Thanks for the help.


Adam

__________________
Central IL
1977 450SL - Orange Julius

1982 300D - Blue Steel

2014 E350 Coupe
1992 Ford Ranger

It's not terribly difficult, just maddeningly time consuming .

I recently got a used W123 sender that "I cleaned it !" , it worked slightly better than the one in my car until it stopped last week .

I took it out and apart today, it wasn't cleaned and never had been , lots of the coffee grounds looking crud inside the bottom and the delicate thin wires were dead black so I guess it's one more I'll have to do my own self .

FWIW, the low fuel lamp isn't supposed to illuminate until the needle is blow the "R" mark, then you should get at least 100 miles more before running dry .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thanks again for the info. I misspoke above, the needle topped out at between half and 3/4. Just confirmed that again by filling up. Side note calculated my MPG to be about 20. That's seems low, although there has been plenty of idling and reving and driving around town in S while I futz with the cold idle.

At this point I'd remove the sender (yes, it's a messy job, you'll need to fold a towel up to catch all the Diesel fuel drips, I like to raise up the sender in it's hole _almost_ all the way and gently stick a flat blade screw driver between it and the hole to allow it to drain before fully removing) and plug it in and turn the key on and tip it up to test it ~ if the gauge reads full when you hear the float slide to the top and stop, then tip it the other way and watch the gauge as the float slides down again, if you tip it vertical the gauge should read below 'R' and the low fuel lamp should illuminate .

Proper testing is always important .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

That's basically what I did except when I had it plugged in I just pushed it from bottom to top and watched the gauge. It maxed the gauge maxed out at between half and 3/4 with the float at the top. Filling it up this afternoon produced the same result.

__________________
Central IL
1977 450SL - Orange Julius

1982 300D - Blue Steel

2014 E350 Coupe
1992 Ford Ranger

Maybe it's time for a new gauge head ? .

I may be closing in on this too, my gauge stopped coming to life when I switch on the ignition, I have to drive a few blocks or further before it springs to life .

Interestingly, the low fuel lamp comes on but the needle proper sits dead, I tried banging the dash in case of loose wire but no joy .

I then rolled all the copper fuses to make sure I had good power, still no joy .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I think I'm just gonna live with it for the time being. Next time I have a need to get back into the cluster (or the first time I run out of fuel LOL) I'll investigate further.

__________________
Central IL
1977 450SL - Orange Julius

1982 300D - Blue Steel

2014 E350 Coupe
1992 Ford Ranger

When I purchased my E300D, 12 years ago, the fuel gauge was erratic.

After a few hundred miles and a can of Sea Foam in the fuel tank, the gauge has never been erratic again. I use Sea Foam, 2 cycle marine oil, Power Service Diesel Kleen, and Stanadyne mixed together to make my own diesel additive. Typically add about 16 oz to a 20 gallon fillup. Could probably do a better mix but seems to work for me.