Extra air in my primary fuel filter????? - PeachParts Mercedes-Benz Forum

Austin85 · #1 11-17-2005, 02:22 PM

I have been running 2K miles on WVO blend, and finally have clean primary filter for last 300 miles.....
But last nite I started loosing power and at idle Tach was down to 500rpm, and stalled once....
Checked the primary and pumped manually, and it looked as if the fuel was draining back into the line...and the filter wouldn't stay full.
I am guessing this is why I was loosing power, I checked the hoses and they look strong; tightened the clamps up..but still get a little extra air pocket in the primary....
Anyone have a clue what is causing this ???? What to check for???

**One thing I did notice was the 2 lines that come out of the tank on the passenger side have a rubber stopper gasket they come out through; This felt worn and soft.....

boneheaddoctor · #2 11-17-2005, 02:36 PM

Quote:

Originally Posted by Austin85

I have been running 2K miles on WVO blend, and finally have clean primary filter for last 300 miles.....
But last nite I started loosing power and at idle Tach was down to 500rpm, and stalled once....
Checked the primary and pumped manually, and it looked as if the fuel was draining back into the line...and the filter wouldn't stay full.
I am guessing this is why I was loosing power, I checked the hoses and they look strong; tightened the clamps up..but still get a little extra air pocket in the primary....
Anyone have a clue what is causing this ???? What to check for???

**One thing I did notice was the 2 lines that come out of the tank on the passenger side have a rubber stopper gasket they come out through; This felt worn and soft.....

THere is usually an air pocket in that filter..however its rare for that to drain out or empty out, particularly while running. Those rubber lines sound bad...they should feel firm...but not hard and simular to other lines that size on the car.

I would replace suspect rubber lines...they are fairly cheap.

New2MB · #3 11-17-2005, 02:51 PM

Quote:

Originally Posted by boneheaddoctor

THere is usually an air pocket in that filter..however its rare for that to drain out or empty out, particularly while running. Those rubber lines sound bad...they should feel firm...but not hard and simular to other lines that size on the car.

I would replace suspect rubber lines...they are fairly cheap.

What do you use for vacuum lines? The vacuum lines I replaced swelled when I got gas on them because they are the cheap EPDM. If I want a line that won't swell I have to get a fuel line but the fuel line is too big and creates a small leak. So I put the old lines back on for now, it's hard to beat MB OEM.

boneheaddoctor · #4 11-17-2005, 02:59 PM

Quote:

Originally Posted by New2MB

What do you use for vacuum lines? The vacuum lines I replaced swelled when I got gas on them because they are the cheap EPDM. If I want a line that won't swell I have to get a fuel line but the fuel line is too big and creates a small leak. So I put the old lines back on for now, it's hard to beat MB OEM.

Fuel lines should be real fuel line material or preferibly Viton for Biodiesel compatibility, not just something that fits..

Vacuum lines I use what fastlane carries...so far it has served me well, not sure the manufacturer or material to be honest. I have none left but a 4" piece to look at. THe Injector return lines I use MB OEM stuff ...its good quality and is Biodiesel resistant. I usually run B20

Austin85 · #5 11-17-2005, 03:07 PM

Quote:

Originally Posted by boneheaddoctor

THere is usually an air pocket in that filter..however its rare for that to drain out or empty out, particularly while running. Those rubber lines sound bad...they should feel firm...but not hard and simular to other lines that size on the car.

I would replace suspect rubber lines...they are fairly cheap.

I'm not saying it drains out while runnnig. It does drain out when off and I am priming the pump to fill the primary.....I am asuming the loss of power is a result of something here. Possibly air getting in my lines somewhere. The lines feel good, but I will replace soon with 3/8 fuel line from AP store...
What about that rubber gasket at the tank????

boneheaddoctor · #6 11-17-2005, 03:09 PM

Quote:

Originally Posted by Austin85

I'm not saying it drains out while runnnig. It does drain out when off and I am priming the pump to fill the primary.....I am asuming the loss of power is a result of something here. Possibly air getting in my lines somewhere. The lines feel good, but I will replace soon with 3/8 fuel line from AP store...
What about that rubber gasket at the tank????

Around the filler neck? I would expect teh see a small increace in bubble size when off...but draining back is telling me you have a air leak which is bad....you need to find that for sure. THat will be between the filter and the engine most likely.

THe "Stopper" gasket I am not sure what you mean....It might be to keep the elements out as tank is inside the car....that is one I would not worry about. I am assuming you mean where the return line and tank breather go inside to the tank.

Austin85 · #7 11-17-2005, 06:40 PM

Quote:

Originally Posted by boneheaddoctor

Around the filler neck? I would expect teh see a small increace in bubble size when off...but draining back is telling me you have a air leak which is bad....you need to find that for sure. THat will be between the filter and the engine most likely.

THe "Stopper" gasket I am not sure what you mean....It might be to keep the elements out as tank is inside the car....that is one I would not worry about. I am assuming you mean where the return line and tank breather go inside to the tank.

Yes, it's the gasket at the return line and other line next to it.
If there is a leak of air between the primary and the engine..?? Does the manual primer pump have a closed or lock position? Possible air getting in through there???

boneheaddoctor · #8 11-17-2005, 07:35 PM

Quote:

Originally Posted by Austin85

Yes, it's the gasket at the return line and other line next to it.
If there is a leak of air between the primary and the engine..?? Does the manual primer pump have a closed or lock position? Possible air getting in through there???

If you have the old style primer pump (the one with the white cap you unscrew and pump)..do you see fuel leak when you pump it? If so replace it. if its the black one that is like a sleeve that covers the inner parts that is the new style and unlikely at isse. Are your rubber lines at the primary old or new? and have the hose clamps been tightend so tight they cut into the rubber?

The Old stlye pump screws and locks in the down positiion..it has a knurled rim.

THe new style does not lock.....looks like a small hotdog stuffed on a spike. Here is a new style photo

Austin85 · #9 11-18-2005, 01:56 AM

Quote:

Originally Posted by boneheaddoctor

If you have the old style primer pump (the one with the white cap you unscrew and pump)..do you see fuel leak when you pump it? If so replace it. if its the black one that is like a sleeve that covers the inner parts that is the new style and unlikely at isse. Are your rubber lines at the primary old or new? and have the hose clamps been tightend so tight they cut into the rubber?

The Old stlye pump screws and locks in the down positiion..it has a knurled rim.

THe new style does not lock.....looks like a small hotdog stuffed on a spike. Here is a new style photo

It's a black top so it's new and doesn't leak.
and the lines are old and the clamps are tight....