I seem to have air bubbles in the first (primary ) fuel filter.

No matter how I try to bleed the system, the air remains... is this O.K., or should I try to bleed the system better? I do not believe that the fuel hand primer pump is functioning properly.

Sincerely,
Tommy Darcy
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'82 300D (Turbo) c300k miles, "Mary."

I assume that you are talking about seeing a lot of bubbles in the pre-filter at idle.

Do you have any fuel leaking when you use the hand priming pump? Is the pump the old style that is white and unscrew to pump? If so, then the hand priming pump may be causing air to get in the line and should be replaced with the new style primer.

Also, a clogged fuel screen at the tank has been mentioned as causing air bubbles. And depending on the model, a clogged fuel tank vent may cause this.

(BTW, you need to go to "User CP" at the top and edit your signature to include the model # of your car so we know what we are dealing with.)

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Sam

84 300SD 350K+ miles ( Blue Belle )

Yes, fuel pours out of the pump... I'll change it.

I had an old sloop once, with a one-lunger, which when I primed it, would spew fuel... so I assumed it was normal, silly me.

Sincerely,
Tommy Darcy
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'82 300D (Turbo) c300k miles, "Mary."

Usually fuel leaks = air in the fuel system. When you get that primer pump replaced, about $20, it should begin to purr a little better.

(BTW, sorry I did not see the model # in the previous post. Working on a laptop with a small screen and had not scrolled down far enough. )

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Sam

84 300SD 350K+ miles ( Blue Belle )

The prefilter having bubles in it is a fule hose or line leak between that and the tank.....the primer pump can't cause bubbles there......that said...a primer pump thats leaking is also bad....likely two problems rather than one.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Be aware that it is virtually impossible to get all the air out of the prefilter so it is normal to see a bit of air in there, you just don't want too much. If you have a lot of engine vibration the fuel may be foaming a bit and look like bubbles. Most importantly you shouldn't be able to see any air at all in the hard, transparent fuel lines running fron the secondary filter to the IP.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold

Does the fuel in your pre filter turn to foam? I had the same problem last year, my pre filters were leaking air into the fuel at the seam. I replaced three of them before I got a good one.

These filters I got from Fastlane and seem to be of higher quality then the first batch:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1AC0K3S9E1JL1D3ZBT&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1987&product=E1000-97870&application=000046825

Splice in a clear peace of PVC hose to help you track down the leak.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

twdarcy,

Some air in the inline filter is normal. It just stays there above the outlet. If you had a opaque filter, you would never know the air was there. If it passes out of the filted it will go out the bleed hole in the secondary filter and back tio the feul tank.

If the engine runs well with no starting problems, forget about it. If it ain't broke, don't fix it.

P E H