So, I have my new fuel filters and I'm about to change them out this week and I have two dumb questions.

1) Everyone says that it would behoove me to fill my main filter with diesel to get as much air out as possible before I install it. I'm assuming I want to pour this unfiltered diesel from a gas can into the pre filtering part of the canister and not just over the whole canister. So, do i pour it into the center hole with the threads and fill it or do i pour it into the outside holes? I'm assuming the center hole.


2) It says to put some oil on the rubber gasket, what kind of oil is best?

1) I normally use something like Marvel Mystery oil because it is clean and I never have diesel in a can. Then you can fill it completely from all the holes.

Fill it up right before you screw it on.

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2006 E320 CDI
1992 300D - 5speed manual swapped

former members
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1978 300CD "El Toro"

I am curious to know: where did you read that?

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

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It's generally a good practice to lubricate seals before install with a compatible fluid. In this case most anything will work, including the very diesel being used. Or diesel purge or ATF or clean engine oil.

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In practice filling the Filter with unfilter Diesel Fuel causes no issues. Obviously your container of Diesel Fuel needs to be clean and don't shake it and stir stuff up.

I don't fill the Filter as I easily spill stuff so I get on the Hand Primer and pump till I hear a buzzing, squishing, squealing sound from the Fuel Pressure Relief Valve and than I pump some more.
That is supposed to clear the Air out of the Fuel Supply System

If I did no pump enough and got Air in the Fuel Injection Hard Lines I would have to loosen the Fuel Injection Hard Line Nuts at the Injectors and crank until the Air is out and then tighten

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84 300D, 82 Volvo 244Gl Diesel

I just fill the new filter from the old. I've dumped the old filter out ad never had much dirt. Search on "lubricity study". You may exclude things like transmission fluid and MMO from your list of acceptable products to burn in your engine.

I add 1oz of 2-stroke/gallon to the fuel. Oil is required more by the diesel ram with its expensive, failure prone injection pump then the lovely trouble free 617.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

In that case, why even replace the filter? That has to be one of the worst ideas I have heard in a while.

In my opinion, all this "filter filling" is much ado about nothing. The primer pump isn't there to serve as a decoration. Use it.

Same with "gasket oiling." The filter doesn't need to rotate, so why should it need lubrication?

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i agree

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83 300CD- sanden, dual p/f condensers, 160a alternator, ect
91 300TD- 722.6, #22 head, 3.5L IP, w140 manifolds, ect

I always fill the secondary filter. I think it is a matter of personal perference. Filling it is better as there is no wear and tear on the primer pump and much less effort. Smearing the rubber seal with diesel or oil is also a matter of personal perference. Most people do it. I would not fill the new filter with diesel the old. Would it do any harm, probably not.

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I read about oiling the seal from the directions on the filter, lol.

My question about filling the filter I think was misunderstood. Maybe because I'm totally over thinking it. On the top of the filter there is a hole in the center and then smaller holes on the outside. I would imagine that fuel goes in the center hole, filters and comes out the small holes. So, by nature of this, wouldn't i fill it with fresh diesel from the center hole? Or does it not matter and I just put it all over the top of the filter.

Yes, this is a time / labor saving suggestion.
I use clean diesel, 2-stroke oil, ATF, engine oil, Marvel Mystery oil, diesel911, hydraulic oil, virgin vegatable oil, etc, etc.
Never had any issues, unless the ambient was sub-zero.


2) It says to put some oil on the rubber gasket, what kind of oil is best?
ANSWER: This is a personal choice, I usually do it by reflex, but forget often enough to prove it is not critical.

.

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I usually take the opportunity to fill it with something that will help clean the IP and the injectors, usually something like Marvel Mystery Oil, or Diesel Purge or Sea Foam.

It doesn't matter which holes you use at this point, all you're doing is filling the filter with clean fuel or fuel additive. I personally pour it in the middle hole.

I either use some clean diesel to lube the gasket or some clean motor oil.

I realize you're just asking questions, but you are over-thinking this.

Packman

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83 240D - 4 speed manual - Manilla Beige
189K miles, Tachometer mod, cool wooden shift knob from PeachParts, CocoMats, Original factory paint, manual windows, manual sunroof. Starting to add AudioWrap to this car too!

I'll say what I do.

I use ATF to fill the filter most of the time. ATF SHOULD be the cleanest oil you can find since transmissions are so sensitive. Conventional ATF specifically since synthetic oils don't burn well.

I pour it in the outside holes. If it's like the prefilter, the oil goes from the outside holes through the media and into the center of the filter.

I usually get the ATF on the gasket anyway, so I spread it evenly around the gasket making sure no dirt is stuck to it.

Then I replace the bolt O-rings and lube those too. Reinstall, crank, and go.

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It should cut around 20 seconds off the priming process. If you can find some appropriate fluid, fill the new filter and clean up the mess in 19 seconds or less, you will have saved time.

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