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Hello, Benz friends.

I'd like to try my hand at replacing my own fuel filter on my '81 240D and was wondering if any of you would be willing to walk me through it, or if there is a tutorial I haven't yet found. Any help you could offer would be much appreciated!

-Danielle
 

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It's a spin-on over on the passenger-side fender. Have to hold the nut on the top with wrench when removing/installing. There's a little one on the driver side down on side on engine, too.

Your car is a W123, and more people will see your questions if posted in that specific forum.
 

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Yes, there are two filters, the primary, usually a clear inline affair and the screw on one. When installing the new spin on filter, secondary, fill it with fuel, this will negate the need to prime the system after.
You may have a crush washer just under that big (24mm) bolt in the center of the housing, the one I have my finger on. I use a composite washer I got from the hardware store, works fine. If you don't have a washer there now, don't put one on. You will have one or two "O" ring washers on that bolt, a banjo bolt. Depending on their condition, you may want to replace them, your local auto parts store should have them. Or these folks have 'em.
https://www.autohausaz.com/search/product.aspx?sid=mqqie055kwmqfx45rowxi455&[email protected]&[email protected]&year=1981&[email protected] & Air System&[email protected] Filter Seal
Happy wrenching.
 

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I'd recommend getting the parts beforehand so you know what to look for. Be sure to ask for primary and secondary filters.

Before you open the fuel system, disconnect the negative terminal from the battery.
The large cylinder filter does screw right off and on again, I use a wrench on the through bolt (the head of which is visible above the filter) to loosen it a little before unscrewing, and then to tighten it again after putting the new one in. The old filter will be full of diesel, which you can pour right back in the tank.
The smaller plastic filter is just behind the large one, next to the injector lines. It is attached to the fuel line with a screw clamp on each side, just loosen the screws and swamp em out.
Bleed the fuel system by unscrewing the plastic knob near the little fuel filter and giving it a little pumping.
Then reconnect your battery and crank her up.

Unless you think the old filters are a lost cause, you might find it worthwhile to hang on to them just in case. I haven't experienced it, but i've heard tell of sudden losses of power due to a bad batch of diesel or something clogging filters on the road.

Welcome to the forum!
 

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You may have a crush washer just under that big (24mm) bolt in the center of the housing, the one I have my finger on.
Mine is a 22mm. :confused:
 

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Hello, Benz friends.

I'd like to try my hand at replacing my own fuel filter on my '81 240D and was wondering if any of you would be willing to walk me through it, or if there is a tutorial I haven't yet found. Any help you could offer would be much appreciated!

-Danielle
Hi Danielle!
This is a very easy job except for finding a large 24mm wrench for the screw-on filter! I did not own a wrench that large when I started doing my own filters. I change the screw-on filter every 10,000 miles. I change the little clear plastic filter every 3000 miles same time I do an oil change.

Have fun, filters are easy!
 

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Service manual calls for replacing the fuel filter every 30,000 miles and checking the pre-filter every 30,000 miles. When I drove my 240D a lot, I serviced it on the severe service schedule which meant replacing them every 15,000 miles. Now that I drive it less than 1000 miles a year, I'll probably do it every five years or so. We all have our own ways of wasting money in other people's eyes, so you certainly won't be doing any harm by changing it more often, but it's pretty major overkill unless you've got a bunch of crap in your tank.
 

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I've done the job with an adjustable wrench because I didn't have a 24MM wrench at the time. It shouldn't be too hard to loosen, so the adjustable wrench works just fine.
 

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Service manual calls for replacing the fuel filter every 30,000 miles and checking the pre-filter every 30,000 miles.
I couldn't imagine leaving the little plastic pre-filter on for 30,000 miles. Mine gets dirty every time I drive on a low tank. Yes, I assume I have crud in my tank! So I change my filters on the regular. They are relatively inexpensive.
 

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Unless you think the old filters are a lost cause, you might find it worthwhile to hang on to them just in case. I haven't experienced it, but i've heard tell of sudden losses of power due to a bad batch of diesel or something clogging filters on the road.
Funny story-- I don't know whether to call it a jinx or good luck, but the first time I drove today after commenting on this thread, my engine started shaking badly at idle and accelerating sluggishly. Swapped in the spare filters and 5 minutes later I was happily back on the road. What a coincidence!
 

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I certainly would not carry around my used filters, but I always do carry a set of new ones with me just in case. However, since I have owned the car for 27 years, I have never had a bad fuel problem and have never needed my emergency filters that I carry around with me.
 

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I carry a set of new filters and a small tool box just in case.
 

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I probably should carry some spare filters and belts etc. I ALWAYS keep a jug of oil in the back just in case however. Seeing as how oil is the lifeblood of these engines I never leave home, or anywhere for that matter, without it.
 

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Seeing as how oil is the lifeblood of these engines I never leave home, or anywhere for that matter, without it.
Good call Matt!
 

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I ALWAYS keep a jug of oil in the back just in case however. Seeing as how oil is the lifeblood of these engines I never leave home, or anywhere for that matter, without it.
I can see carrying a quart or two of oil, but carrying around a jug of oil at all times just seems like extra weight to me. A jug's what, 5-6 quarts? I don't see the need to carry that much at all times unless you're burning or leaking a quart every 1,000 miles or less.
 

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^^I don't roll around with it full. I just keep enough in there just in case there's ever a need for it. It's half filled at most. The car doesn't burn that much oil but I keep some with me just in case. Again, it's for peace of mind.
 
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