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This past week, with having only owned it 8 days, and it being my first MB as well as my first diesel, I took my SD on a long trip...700 miles the one day and the return being 850 miles or so a few days later. Everything worked as it should with the exception of the clock, which seems to stop on occasion, on the outbound leg of the trip. The clock is not the problem...I own a watch.

The problem popped up as follows: At one point when leaving a restaurant, the Anti-Lock light came on. After arriving to my hotel, I turned the vehicle off and back on and the light went out. The next day, having stopped somewhere, when I got back in the car I'd lost air conditioning. Checked the fuses and none were blown, but the no. 11 fuse block had some discoloration on one blade...looked like it had gotten hot. Also, after I checked the fuses and actually changed the no. 11 one (belts and braces), I lost my tachometer as well. I swung into a place run by a friend and found that I had "dirty" power to the no. 11 fuse. It would not stabilize. I also saw one European car expert who pointed me to another shop specializing in older MBs, but due to communication device issues, we didn't really get to talk. As his business card didn't list an address I couldn't drop in and our phones kept cutting out...but he did suggest the OPR as the culprit. BTW...I had also checked the fuse in the OPR and found it was a 20a unit instead of the 10a I now know should be in there. Perhaps I should mention that this trip was on a couple of days of 90F + temperatures.

I decided to drive on through the night from Florida to Tennessee. The car worked wonderfully for the next 400 miles except for the AC and the tach, and the engine temp gage was reading incorrectly. At one point, being bored, I reset the clock and even it kept perfect time for the duration of the trip...a first. However, as I got into hilly and then mountainous areas, she lost all uphill power, to the point that coming up one of the gaps between Asheville and my home I was climbing at 35-40mph. Still, I got across the mountain and back to my home. I ordered MB original OPRs (one for replacement, one for the boot) yesterday.

This morning I went to move the car as I intend to do the ALDA (ADLA?) cleanup today. First thing I noticed was that the clock had gotten off again and then, upon startup, that the tach was working. I let her warm up a touch and then tried the AC....working a treat again! I have not taken the car out on the road yet to check her hill climbing function. I will also check that the throttle linkage is in good shape and doing what it should do, having read that they can cause issues with not getting full power, but I doubt this as a problem...car worked fine on the flats.

So that's the whole story.

As I said, I'm going to do the ALDA cleanup and will replace the OPR. I am also tempted to check the alternator regulator. I ask for any thoughts on my situation from the brain trust that is this forum, please.

Thanks all, Glenn
 

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Disconnect the battery, take out all the fuses, clean all the terminals in the fuse box with a brass brush. Replace all the fuses with fuses that have brass conductors. Bend all the tabs so they make solid contact with the fuses. Reconnect the battery and see if your problems are solved.

You could also have loose/corroded connections under the fuse box, too.

I hate TLA's; what's an OPR? (Operator?) Do you mean OVR?
 

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Generally, I hate them too, John. My apologies. Overload Protectrion Relay, although I’ve seen it as Over Voltage Relay as well.

Thanks for the tip...I’m going to do just that. This car belonged to a collector as a long distance driver. I have found today that the primary fuel filter has filled with crap in the 2500-3000 miles I’ve put on it. Also, the electrical issues. I think perhaps it had been much longer since being used than I believed. This is not to be confused with “led to believe” as I never really asked. Just a few minutes ago, coming back from some errands, the Becker Gran Prix, which previously only played through one front speaker, started working perfectly. Apparently she needs exercising!
 

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Unlike gassers, the diesel fuel filters DO need to be changed regularly - both the inline and the screw-on, big-daddy filter. I always carry several of the inline filters in my trunk and I "try" to keep a screw-on as well, for good measure. A tank of dirty diesel can ruin your day quickly. Not usually a problem, but if you are "in the back of beyond" and get some dirty fuel in your tank, the extra filters can be the difference between getting there, and not!

Rob
 

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Thanks, Rob.

Yesterday, checking on something else, I did find that my filter was very, very dirty. I am beginning to think that this car has sat for good while, I ordered 6 primary filter, one of which I installed today. Will keep some with me along with necessary tools and keep changing them until they stay moderately clean. The one which was in it when I bought it 2500 miles or so ago was perfectly clean at that time.

The next thing I need to do is to adjust the throttle linkage...there is 3/8ths of an inch or more travel left in the linkage when the pedal is on the floor. This is a 1985 300SD and I’m having trouble finding a manual. I sure hate to spend the kind of money people are wanting for them on eBay, etc.

Glenn
 

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Thanks, Rob.

Yesterday, checking on something else, I did find that my filter was very, very dirty. I am beginning to think that this car has sat for good while, I ordered 6 primary filter, one of which I installed today. Will keep some with me along with necessary tools and keep changing them until they stay moderately clean. The one which was in it when I bought it 2500 miles or so ago was perfectly clean at that time.

The next thing I need to do is to adjust the throttle linkage...there is 3/8ths of an inch or more travel left in the linkage when the pedal is on the floor. This is a 1985 300SD and I’m having trouble finding a manual. I sure hate to spend the kind of money people are wanting for them on eBay, etc.

Glenn
You might consider putting a biocide additive into the tank, just in case there is some algae growth going on. Optimally, a tank drain and/or cleaning, but that's a LOT More work. My car sat for about 2 years with fuel in it. After putting the new engine in, I was concerned, but had no issues whatsoever. Diesel lasts a LOT longer than gasoline before it causes problems.
 

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You've been given excellent advice so far. My stinker sat for a while too and the first 1000 miles uncovered many bugaboos.

As mentioned, plan on carrying (and installing) more filters until you get the crap out of the tank. EASY to pull the sending unit tube and peer down into the tank with a strong flashlight to determine what's going on in there. The algicide step may be the whole key, but you have to get that crap out one way or another.

Prob a great idea to run a can of diesel purge through it since that crud will wind up in the pump, the injectors, the lines, etc. Made a world of difference on my 617.

Google "diesel purge". There are lots of YouTube vids, tutorials, etc. Easy, effective and cheap.
 

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You might consider putting a biocide additive into the tank, just in case there is some algae growth going on. Optimally, a tank drain and/or cleaning, but that's a LOT More work. My car sat for about 2 years with fuel in it. After putting the new engine in, I was concerned, but had no issues whatsoever. Diesel lasts a LOT longer than gasoline before it causes problems.
That's true now because of ethanol. Gone are the days when you might start a petrol car (eventually) after ten years sitting. Petrol has a short shelf life now unfortunately.

Diesel, does it not depend on climate a bit? The algae thing is a real problem sometimes. Water in the tank getting pulled through, etc?
 

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Thanks to all on the biocide and old diesel remarks. I have some biocide doming in shortly. I believe algae is likely the culprit here.

I couldn’t agree more on the old fuel thing...I have a significant collection of older vehicles and even though I tend to run ethanol free fuels I still (try to) drain those I am mothballing for a while.

All that said, diesel is a brand new world for me. I had no idea algae could grow in the fuel until speaking with my cousin the other day,

Anyway, I’m on it.

Since I seem to be getting great advice here, I will ask one more thing about manuals for these cars. I have seen CD manuals which say they cover all years, etc. etc. my SD, being a 1985 model, seems to have a number of differences to earlier years. For this reason, i wonder if the “all years” manuals actually cover these differences. My ignorance promotes fear, and I do intend to check out the online manual today if I can get my Mac to work with the flash files, but eventually I would like a more user friendly accessibility. On my Land Rovers (early ‘60s models), I keep a manual on my iPad and phone...love that...but I still prefer paper in the shop.

Thanks again, all. This is a great forum and I appreciate it!

Glenn
 

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Actually, the algae cannot grow unless there is water in the tank. It grows at the interface between the fuel and the water, in the water.

Change the pre-filter if it looks bad and the main filter if you have a drop in performance. You'll be fine. If you continue to have issues, run the tank down then drain it.
 

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Good info, John! Thanks for MORE of that!


Actually, the algae cannot grow unless there is water in the tank. It grows at the interface between the fuel and the water, in the water.

Change the pre-filter if it looks bad and the main filter if you have a drop in performance. You'll be fine. If you continue to have issues, run the tank down then drain it.
 
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