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Old 04-06-2002, 09:29 PM
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Join Date: Jun 2001
Posts: 46
300 SD Turbodiesel fuel leak!

Im hoping this is a minor problem, but since im new to these things I have no idea what the part is called. I discovered I have a bad fuel leak today. It is gushing out of around a small white/yellowed plastic ribbed thing, right where the fuel filter and line go into. Is this the primer I keep reading about? what the heck is a hand pump? What a strange looking thing. Fuel is gushing out from the base of this plastic thing. Can anyone tell me whats going on here, what do I have to replace? The whole thing sticking out of the side of the block or just this plastic 3 inch thing? THANKS to anybody that replies!
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Old 04-06-2002, 10:02 PM
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Join Date: Jan 2001
Location: Tucson, Arizona
Posts: 758
Primer pump gone Bad

Greetings, and Welcome to this site,

The part you are describing is the fuel primer pump. It can be ordered here at this site for less than $20 and will cure your problem. The o-ring in these older designed primer pumps just get worn out and cause them to leak. If you order the Bosch new design I feel that you will have a trouble free unit for quite a few years as it is redesigned and works much better. If you are unclear which part to order just post your year, model and make and I will get the p/n for you off this site. In the search you can use primer pump entry which should get you there.

"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan
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Old 04-06-2002, 11:22 PM
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Join Date: Jun 2001
Posts: 46

Hey thanks for the quick reply! I found it on Fastlane. How does that primer pump work? You just push up down on it and it springs back ? This is what you use when you change filters or run out of gas huh? I changed the clear plastic fuel filter, but whereabouts is the Primary? cannister filter located?
These engines just look so strange to me after working on american cars all my!
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Old 04-06-2002, 11:53 PM
Join Date: Jul 2001
Location: Old Lyme, Connecticut
Posts: 3,596

The primer pump is located on the front end of the fuel injection pump, which is the device with the bent tubes running up to the fuel injectors. The pump provided with the car originally has a plastic handle with rough knurling around the rim. When it is stowed, or not in use, it is supposed to be screwed down in the stowed position. If it is not screwed down it will likely leak a lot more than when it is stowed. When you use it you unscrew it, then lift the handle and push it down, and depending on why you are doing this, it could be a long time before you are done.

I have never used the new ones, but they apparently do not get screwed down into a stowed position when they are not in use, and they do not have the offensive, sharp knurling on the pump handle. The original ones can wear the skin off your fingers.

The primary filter is located at the front of the engine on the driver's side (in the US), just inboard of the power steering pump. You can see some fuel lines that go to the filter mounting structure. In the old cars the filter was similar to the engine oil filter, as it fit in an aluminum container. The newer ones have spin on filters that look like spin on oil filters. You cannot miss the fuel filter.

Good luck and I hope this helps. Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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Old 04-07-2002, 02:17 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
The new primer pump has a return spring in it -- just push to operate. Much nicer than the older ones. Leak a whole lot less, too.

A new pump will probably increase your milage substantially!

1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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Old 04-07-2002, 05:50 PM
Registered User
Join Date: Jan 2001
Location: Tucson, Arizona
Posts: 758
Order it and Change it

Greetings S-Class,

The info in the above posts are correct and the new primer pump is user friendly, changed both of the old ones out I had on the cars to the new design. They are easy to install, easy to use, and if your current old type is leaking much fuel then your mileage will most likely double as they can leak more than the engine requires to idle. If you decide to change out the main fuel filter, I'd recommend filling it with fuel before spinning it on just to save pumping time on the primer.

"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan
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