83 300sd fuel gauge

[tkocp07]

Hello,
I recently joined the MB diesel world when I bought an 83 300sd yesterday. the car runs well but it has some problems. Almost nothing work(ed) electronically except the heating/air. This morning I began to replace fuses and now the blinkers, and power seats are working. The back right window goes down but doesnt roll up (another story). The lights on the dash so light up (battery light, glow plug light etc) however the fuel gauge, speedometer etc. arent working. Any idea of what that could be or how to fix it? I was wondering if a fuse controls that or if their was another way to go about taking care of that. Any suggestions are greatly appreciated!

Thanks!

[Junkman]

Contacts in the fuse box frequently corrode. They need to be cleaned and tested via voltage drop to know that electricity is flowing correctly.

At least one glow plug is likely bad if the light doesn't work. dieselgiant has pics & process for diagnosing. Replace with Bosch only. Hook battery to plug to test. Again, see DG.

Speedo is mechanical. You probably need to replace the gears. I think spedometergear.com has them. I'd liike to figure the specs because the gears are only a dollar or 2, not $30 that they charge.

Window is fuse, switch wiring or motor. They are fused diagonally ie L front & R rear. FSM and also youtube has proper method for disassembling console to pull switch.

FSM has removal procedure for door trim & window regulator. Lift door card straight up. Pulling out will break the plastic tabs. If you pull the regulator, clean slide channels completely & lube. MB has proper lube. Perhaps so does this site.

You also likely have vacuum leaks but that is another thread. Lots of info if you look.

[tkocp07]

Thanks so much for the info! a lot of stuff to start looking at. I am going to finish replacing the fuses this weekend, and take it to an MB mechanic to check out the vacuum leak. When it comes to cleaning the fuse contacts, whats the best way to do it? Ive seen sandpaper some places. Any suggestions would be great.

[tyl604]

Don't waste your money having a MB mechanic check out the vac issues. They all have them and they are all easy to find and easy to fix. Just get a Mityvac and look up vac problems on the forum. Start with the lines under the carpet in the floor, passenger side front if your door locks do not work. You can block the lines off one by one and figure out how to get the door locks working. The tranny and engine shut off and brakes are on a separate system under the hood (door locks have a vac pump in the trunk - they are not, repeat not connected to the transmission or heat/ac or engine shut off). Also you can completely block off the lines to the EGR; absolutely not needed.

If the tranny shifts not quite right, check for a vac leak before fooling with the vac modulator on the transmission.

If you have power problems engine-wise, look up switchover valve problems here. Easy fix. And once the turbo powers up you will be relatively happy with the power and pickup - just remember it's a diesel.

If you have any smoke in the cabin, your return pipe on top of the breather has come loose or the return tube underneath did not get connected right the last time it was off.

There are dozens of questions to ask and someone will generally have an answer because they have been there before.

It's a lot of fun and quite rewarding if you view fixing the problems more like a treasure hunt than a chore. It's really a great car.

Also give us some pics; preferably before and after. And info - mileage, what works, what does not, etc. You will find a lot of interest and a lot of help on the forum.

[tkocp07]

Thanks for the advice! I am having some tranny issues, it shifts hard going from first to 2nd but is fine after that. The previous owner said that this could be a vacuum problem. Anywhere I could look for more info on how to diagnose/fix this? I can post pics later this week!

[hangit]

Look in the DIY section of the forum. You will find just about any system and topic. As mentioned, dieselgiant.com also has a lot of DIY info.

Good luck.

John

[rsterling]

I just bought my 83 300 SD …. fuel previous owner said fuel gauge is actually on reserve when it gets down to 1/2 tank, which is about right when I filled it. Any easy fix without replacing the whole gauge like the garage wants to?

[bmor_62]

you can pull out the fuel sending unit from the rear storage department and CAREFULLY clean it an re-install, this should give you accurate readings. I need to do this as well but haven't yet. Others may provide more detail if needed.

As for windows, cleaning the switches by the shifter is a good place to start after checking fuses, there's a DIY for this somewhere.

I love my '83, best car I've ever owned, and I ain't young.

[toomany MBZ]

Agreed, it's not the gauge, it's the sending unit.