fuel filter change - Page 2 - PeachParts Mercedes-Benz Forum

d.delano · #16 01-13-2005, 02:43 PM

ah ha. OK. sorry.

but- are you saying you disagree with the others' statements about not noticing ANYTHING till the filter plugs up?

deeph8 · #17 01-13-2005, 03:29 PM

I replaced my fuel filters about a week ago. I filled the new one with diesel purge product rather than old fuel. Anyway, I now have a significant amount of air at the top of the clear plastic inline filter. Is this bad? I am hesitant to use the primer because this caused me a lot of grief on my 1981 diesel. I tried loosening the bolt at the top of the main filter while the engine was running but the air did not go away (and I made a real mess).

franklyspeaking · #18 01-13-2005, 06:34 PM

Air in the pre-filter will not cause a problem. There is a replacement primer available for about $10 that will correct your problem with the old primer and give you the ability to prime the system after filter changes. About the best investment that I have made in my 10 years of 240D ownership.

Old300D · #19 01-13-2005, 06:34 PM

Quote:

Originally Posted by deeph8

I replaced my fuel filters about a week ago. I filled the new one with diesel purge product rather than old fuel. Anyway, I now have a significant amount of air at the top of the clear plastic inline filter. Is this bad? I am hesitant to use the primer because this caused me a lot of grief on my 1981 diesel. I tried loosening the bolt at the top of the main filter while the engine was running but the air did not go away (and I made a real mess).

Visible air in the primary filter is no big deal. It always has an air pocket in it. The primer is specifically for repriming the system after a filter change -- just drop the spin-on, fill it with fresh fuel, diesel purge, or nothing, then prime it. After it stops hissing, it should be primed and ready to start.

I just changed a filter this weekend because my performance seemed to be dropping off -- I started noticing this 2 weeks before. I had some particles in the primary filter, so I replaced both. Performance restored.

deeph8 · #20 01-13-2005, 06:37 PM

do you pump the primer before or after tightening the bolt on top of the fuel filter?

Old300D · #21 01-13-2005, 07:12 PM

Quote:

Originally Posted by deeph8

do you pump the primer before or after tightening the bolt on top of the fuel filter?

Tighten the filter completely, then prime. Air is purged out the cigar hose to the tank.

franklyspeaking · #22 01-13-2005, 07:21 PM

The Haynes manual that I have says to loosen the filter bolt and pump the primer until no air bubbles can be seen coming out around the bolt. That's the way I have always primed the system. Anybody know what the FSM manual prescribes?

deeph8 · #23 01-13-2005, 07:31 PM

I read that also and tried it without luck. How can anyone see bubbles there?

P.E.Haiges · #24 01-13-2005, 07:53 PM

84300DT,

It not a matter of time or mileage but how much dirt is in the fuel you get or if you get fuel contaminated by Fungus that determines how long it will take you fuel filters to plug.

You can't tell when the primary (inline) filter is about to plug by looking at it, even if it is a clear filter. If the engine has full power, that determines if the filters are not plugged. If you notice any power loss, especially on a hill, one of the filters is starting to get plugged. So remove the inline filter and blow backwards thru it. It will be easy to determine if its plugged: barely any fuel will come out of it.

So if the inline filter appears plugged, replace it. If not, put the same filter back in because its the secondary filter that is plugged. There isn't any easy test for this filter, so you probably have to replace it.

Now if you still have a loss of engine power, its probably the strainer in the fuel tank that is plugged with Fungus. You can test for that by removing the rubber fuel line coming from the fuel tank where to connects to the steel fuel line. If barely any fuel runs out, the strainer is plugged and must be cleaned, not replaced.

P E H

franklyspeaking · #25 01-13-2005, 08:01 PM

If you just see fuel with no bubbles, you are primed. It usually doesn't take a lot of pumping if the filter is already full of fuel.

deeph8 · #26 01-13-2005, 09:29 PM

just for grins I tried the primer out b4 driving home (in heated parking garage). I unscrewed the top (as with anything that screws in with this car it was torqued to the max bcz I bought it from frankenstein). Anyway fuel gushed out of the top of the primer, so I quickly screwed it back in. Looks like another project for when warm weather returns (-15F tonight).

Old300D · #27 01-14-2005, 02:44 AM

Quote:

Originally Posted by franklyspeaking

The Haynes manual that I have says to loosen the filter bolt and pump the primer until no air bubbles can be seen coming out around the bolt. That's the way I have always primed the system. Anybody know what the FSM manual prescribes?

I tried it that way the first time I did it. It makes a mess and makes no sense. The cigar hose will pass the air displaced by the primer pump action.

Hit Man X · #28 01-14-2005, 04:02 AM

Changing them is easy, cheap PM... like draining the trans pan w/ converter. It's silly not to do it often.

I do fuel filters every 10K mi, oil every 5K, and drain + fill the trans every 10K mi (AT filter around 30K mi or so). Why? Fuel filters are less than $10. Oil is the life of the motor no matter the cost, and ATF is $1.20 a quart.

P.E.Haiges · #29 01-14-2005, 02:25 PM

Hit Man X,

What is silly is to replace fuel filters that do not have to be replaced.

If it ain't broke, don't fix it also applies to fuel filters.

P E H

84300DT · #30 01-14-2005, 02:39 PM

Quote:

Originally Posted by P.E.Haiges

84300DT,

It not a matter of time or mileage but how much dirt is in the fuel you get or if you get fuel contaminated by Fungus that determines how long it will take you fuel filters to plug.

You can't tell when the primary (inline) filter is about to plug by looking at it, even if it is a clear filter. If the engine has full power, that determines if the filters are not plugged. If you notice any power loss, especially on a hill, one of the filters is starting to get plugged. So remove the inline filter and blow backwards thru it. It will be easy to determine if its plugged: barely any fuel will come out of it.

So if the inline filter appears plugged, replace it. If not, put the same filter back in because its the secondary filter that is plugged. There isn't any easy test for this filter, so you probably have to replace it.

Now if you still have a loss of engine power, its probably the strainer in the fuel tank that is plugged with Fungus. You can test for that by removing the rubber fuel line coming from the fuel tank where to connects to the steel fuel line. If barely any fuel runs out, the strainer is plugged and must be cleaned, not replaced.

P E H

thanks peh, that answers that question. i think i will leave my spare filters in the glove compartment safe and sound until they are really needed.