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  #1  
Old 01-29-2008, 01:24 AM
Diesel Dan's Avatar
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Question What is that device before the lift pump?

In my '87 300D, there is a device inline right before the lift pump. It also has a couple of fuel hoses that go up to the air intake (??).

The reason I ask is that I have an air leak coming from this device. I have replaced all my fuel lines with translucent polyurethane, so I can see the air bubbles. It happens mainly when I hit the throttle. The only fuel lines I haven't changed out yet are those two that go up to the intake. Is it possible that the device itself could be leaking air? Or is it more like these lines? Or maybe something at the intake?

Thanks

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1987 Mercedes 300D ~200K (Greasecar & Biodiesel)
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  #2  
Old 01-29-2008, 01:33 AM
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I believe you are referring to the fuel heater, it uses coolant ("heatant?") to warm the fuel before it gets to the IP.
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  #3  
Old 01-29-2008, 01:44 AM
lrg lrg is offline
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I agree, you're describing the fuel heater.

Yes it could be leaking but it's as likely to be leaking fuel out as air in. If you don't see some fuel leaks around the fuel heater then the air leak is likely elsewhere. There are a couple of rubber O-rings inside the heater that can be replaced but you'll probably need to get them from the dealer to be sure you get the right ones.
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  #4  
Old 01-29-2008, 03:29 AM
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Diesel Dan,

Not a lift pump, Its a fuel pump that pressurizes the fuel system.

A lift puimp is used on a carburated engine where the fuel is lifted to the carburator bowl and not pressurized.

P E H
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  #5  
Old 01-29-2008, 03:37 AM
ForcedInduction
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Quote:
Originally Posted by P.E.Haiges View Post
Diesel Dan,

Not a lift pump, Its a fuel pump that pressurizes the fuel system.

A lift puimp is used on a carburated engine where the fuel is lifted to the carburator bowl and not pressurized.

P E H
A lift pump is also used on diesel engines where the fuel is lifted to the injection pump and pressurized.

It is a lift pump on the OM6xx engines.
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  #6  
Old 01-29-2008, 03:43 AM
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Forced,

NOPE !!

P E H
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  #7  
Old 01-29-2008, 04:04 AM
ForcedInduction
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Peh

Yep!!!

L M N

Noun 1. lift pumplift pump - pump used to lift rather than force a liquid up
pump - a mechanical device that moves fluid or gas by pressure or suction
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  #8  
Old 01-29-2008, 07:37 AM
Diesel Preferred
 
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All incorrect so far. This is the fuel thermostat, and it controls flow of fuel to/from the fuel heater (which uses coolant to pre-heat the fuel).

It has one o-ring and an internal copper washer that are replacable. Usually only the o-ring needs to be replaced to fix any leaking.
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  #9  
Old 01-29-2008, 11:17 AM
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Quote:
Originally Posted by Maxbumpo View Post
All incorrect so far. This is the fuel thermostat, and it controls flow of fuel to/from the fuel heater (which uses coolant to pre-heat the fuel).

It has one o-ring and an internal copper washer that are replacable. Usually only the o-ring needs to be replaced to fix any leaking.
I guess I'll replace the fuel lines going to and from the thermostat and the heater with translucent lines to see if the air is coming from the thermostat or from the heater.

Thanks!
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1996 Thomas/International Bus with DT466 engine
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  #10  
Old 01-29-2008, 11:23 AM
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you are all wrong...

It's part X-9870-echelon of the revised flux capcitor
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  #11  
Old 01-30-2008, 02:42 PM
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Quote:
Originally Posted by TheDon View Post
you are all wrong...

It's part X-9870-echelon of the revised flux capcitor
What's a "flux capacitor"? Sounds like something on the Starship Enterprise. Does it alter the fabric of the time-space continuum?

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