Yesterday I noticed the tell-tale anemic response of the car (the 91), very suddenly and noticeably, alerting me to the fact that I need to replace my fuel filters...which I will do this afternoon. However, later in the day and this morning, the responsiveness of the car seemed to have improved somewhat.

Question 1: When a clogged fuel filter affects performance, can things get a little better for a while, or do they only get worse? I've only experienced clogged filters one other time, so I don't have a lot of experience.

Question 2: What other problems, other than a vacuum leak of some sort, could produce symptoms similar to a clogged fuel filter? I'm especially wondering what it "feels like" when a fuel pump is about to go.

Thanks.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 160k miles
06 E320 CDI "Rutherford", Black on Tan, 180k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 79k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

When problem goes away after shutdown,its more like the tank screen.Buy startron for diesel engines and use as directed.Or better yet,drain tank and clean screen.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

Yes, sometimes the filter will tend to clear a bit when the engine is shut off, but quickly re-clogs during driving.

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Gone to the dark side

- Jeff

As babymog said; if your Fuel has become contamineted by something growing in it or just bad fuel from the Pump a Filter can clog again quickly.

You often see in Posts something like; I just change my filter last week and now I have the same problem. What is wrong?

To see if it an issue with the Fuel Tank Screen you can swap positions of the Fuel Return Hose and the Fuel Inlet Hose. However, if you do they the Fuel will be drawn from a higher position inside of the Fuel Tank and you need to keep the Tank above 1/2 full so you do not run out of Fuel. Just do it to test.

To see if it is a restricted Fuel Tank Vent try driving without the Fuel Fill Cap on; but, do not do that on a full Tank of Fuel. Don't want Fuel blowing out on the paint job.

If you still have the Old Filter you could cut it apart and take a look at what is inside.

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84 300D, 82 Volvo 244Gl Diesel

In your tank and problem goes away!
Fungus,Fungus,Fungus!

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'84 300SD sold
124.128

I assume something like Bio Kleen works just as well?

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 160k miles
06 E320 CDI "Rutherford", Black on Tan, 180k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 79k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Dump half of it in your tank,(You Cannot "OverDose") ,right now.
[Save the other half for ongoing treatment]
drive around for a couple of days.

It'll clean the Tank Strainer and and your Fuel System without clogging the filters.

Too Easy!

Call them they'll ship direct.
Or find a West Marine.

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'84 300SD sold
124.128

In your car, the ECU manages boost through a vacuum actuator. If the ECU doesn't want you to have boost, it will hold back. By all means change the filters but if the problem persists, check for a vacuum signal to the wastegate actuator when the engine's under load.

Sixto
87 300D

Hey everyone!!

This is my first post, as I'm probably (since I registered 2 minutes ago) the newest member on here... but this site has saved my doopah plenty of times since I acquired my 300D a few weeks ago. Thank you for all your info!

Anyways, I'm about to run a "Hail Mary" test of Startron on my 83 300D. I trailered it home a couple weeks ago, and have been dumping massive amounts of time and work into it, as it's my daily driver. It's a car that's sat for a MINIMUM of 6 months, but possibly over a year easily, due to a couple owners who have little/no diesel or MB knowledge.

I've went through a bit of fuel system repairs.. added the MISSING primary filter (Eek!) and ended up replacing the steel lines as well as the infamous rubber feed line too.

Needless to say, the first primary filter plugged up within 15 miles. Yeah.

I've went through about a dozen primary filters in 4-500 miles.. each one getting clogged up with the icky~sticky blackish gray sludge...

I had to flip-flip the feed/return lines due to the strainer on this past Friday, (Only for a few miles tho) and that filter FILLED with.. um... Jello?

I don't want to pull the tank if I really don't have to, and read a lot of reviews about Startron on here, other MB boards, as well as diesel auto and boat boards... and everyone seems to rave on it's ability to clear the gunk.

So, I went to BP on the corner with it pretty low (1/4 tank) and added 1 8oz bottle of Startron Diesel Enzyme Additive, and filled it up... drove it 1 mile home and it's parked and sitting... I'll leave it for 24 hours, throw a fresh filter on (I'm using cheap KN clear bodied fiber filters for inspection) and see what happens. I'm hoping that I have good news to report within the next few days!

(PS, even tho primaries are easy to change, its not fun doing it in the rain with a 102 fever and a confirmed case of H1N1..... hmm.. maybe I should drink some Startron too..)

If your filters are clogging that quickly, drain the tank and clean the strainer. Removing the tank for a thorough cleaning is ideal but you you can get most of the icky stuff out by draining and whatever rinsing you can do with the tank in place and strainer removed. Think of this way, do you really want your fuel system processing muck dissolved in chemicals?

Sixto
87 300D

i am running into the same problem. i have a 1979 240d with a 5 cyl that someone transplanted in it. lost power, pre-filter black and yucky. changed it and runs like a champ except that the pump doesn't seem to be keeping up. only fills filter ( clear ) 1/3 to 1/2 full. i recently started running some veggie oil blend ( 50% or less ) mixed with reg. diesel. i am sure that has stirred the gunk in the tank. had 3,000 miles on it with no problems until adding the mix. where do i find the two hoses to reverse to flush the strainers? i don't have a history on the car but the odometer stopped at 275k. what would fuel pump symptoms be and is it inside or outside the tank?

thanks in advance

Sixto DOES have a valid point in regards to just pulling the strainer... but if I'm correct, there's an O-Ring that needs to be replaced. I'll call Sparomobile in Downers Grove and get one. I'm not one for re-using any seals..

Now, to back~flush the strainer... it's easy but temporary.. the gunk is still in there. If you pop your hood, you'll see a fuel line going from a steel line to your primary filter, which is in line to the pump. That's the feed line. Now, there's another rubber line going to a steel tube next to that one.. it's swollen, and is referred to as the "cigar tube", and it goes to an oil filter lookin' sorta filter.. that's your secondary filter... that the return line. It's as simple as flip~flopping those two rubber lines where they clamp onto the steel lines! It's a 2 minute job with minimal mess.. then go get it up to a nice cruising speed for a few miles. I do that, but prefer to switch the lines back withing 10 miles, since I'm running without a strainer.. I'd hate to suck up a chunk of rust or a forgein object in the tank and plug my nice new steel lines!

WARNING!!!!!

The return line sits MUCH higher in the tank than the supply line, so MAKE SURE you have OVER half a tank, or you could theoretically run out of gas while the gauge shows you're still fine!!!

I noticed that when I initially decided to flip~flop the hoses for the 1st time.. my spidey senses were tingling and telling me that the strainer was plugged. When I did that, drove for a bit, and flipped the lines and changed filers (see my previous post) I noticed that I was able to fill the filter up via the primer to where it should be.. mine IS full of air again tho... so I can't assure you that it's based on my theory of the IP creating a lil vacuum effect due to a restricted strainer, causing less fuel volume in the filter....

Sixto.. the tank vent is basically a one~way valve on a rubber line under the car, center rear, up by the tank, right??

That's going to depend on what 123 you have, please put that in your avatar or signature. That will help those that are trying to help you.
That will also depend on early or late model 123's, #51 or #73 or #73a.

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83 SD

84 CD

i will try sixto's test of the fuel filler cap and reverse the lines to try and clear the strainer temporarily. how do i get to the strainer? so you replace them or just clean them? should i still put some startron in if i do all of the above? or will the chemicals from blended fuel do the trick?

the learning curve is steep but i am wearing my hiking boots!!!