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Discussion Starter #1
Hi,

I have a 1980 300d, running on vegi, and has been flawlessly for over 1 year.
All of a sudden I am picking up tiny air bubble in the fuel line. I have a clear line that runs from the hard line to my faucet in-line pump and from the pump a clear line to the factory primer. In those clear lines I see tiny air bubbles and sometimes a large air bubble will come along. It drives fine for a while, but as I drive, I will get more and more of the tiny air bubbles, then the car starts surging and sometimes quits all together. I checked the hard line to the tank, no cracks, I have checked the clamps on all my clear lines. I thought the vent in the tank was clogged, so I drove with the gas cap off and still the same problem. Any ideas?

Thanks.
 

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1982 Mercedes 300D Turbo Diesel
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i started seeing air in my fuel filters when my filters started clogging and it couldn't pull enough fuel. have you replaced the fuel filters to see if that's the problem. i ended up pulling the entire veggie oil system when i started having to replace the filters every month. haven't had a problem since then, running straight diesel now.
 

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1983 300D Turbo Diesel
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Discussion Starter #5
brand new filters, made no difference. Also, I am seeing the air before the filter, between the primer and in-line pump. my set up is:

factory hard line from tank
1 ft clear line from hard line to in-line pump
1 ft clear line from in-line pump to primer (small in-line filter before primer is eliminated)

thats it, i also eliminated my extra in-line filter when this problem started because I thought the filter housing might have been leaking.
 

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Discussion Starter #7
even put back to stock with just a clear line connecting the hard line to the primer, I still see air in the fuel coming from the tank?
 

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1984 €uro 300D NA
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Recheck the 17 & 22 mm bolts on the diesel filter head but I bet it's a loose hose clamp allowing air to be sucked in since I believe your fuel system is plumbed to vacuum.

My VO system is re-plumbed to vacuum (stock lift pump just prior to IP) as is the diesel side, but my diesel side has an aux lift pump that I can turn on with a dash switch to create 5 psi which can quickly bleed out any air in the system. My VO side has a three way manual ball valve on the VO return. If there is air on VO I open the valve which has a brass hose barb on the open end. I attach a fuel hose which empties to a plastic bottle. Once I stop seeing air I close the valve.

KISS (keep it simple stupid) was my mantra in designing my system. I have yet to have any air on VO except when I change the VO filter.

There are two hose clamp styles. The standard "worm gear" are crap. Get fuel injection hose clamps. They have a smooth band around the hose and are fastened by a standard screw and nut. Napa carries them.
 

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Discussion Starter #10
Recheck the 17 & 22 mm bolts on the diesel filter head but I bet it's a loose hose clamp allowing air to be sucked in since I believe your fuel system is plumbed to vacuum.

My VO system is re-plumbed to vacuum (stock lift pump just prior to IP) as is the diesel side, but my diesel side has an aux lift pump that I can turn on with a dash switch to create 5 psi which can quickly bleed out any air in the system. My VO side has a three way manual ball valve on the VO return. If there is air on VO I open the valve which has a brass hose barb on the open end. I attach a fuel hose which empties to a plastic bottle. Once I stop seeing air I close the valve.

KISS (keep it simple stupid) was my mantra in designing my system. I have yet to have any air on VO except when I change the VO filter.

There are two hose clamp styles. The standard "worm gear" are crap. Get fuel injection hose clamps. They have a smooth band around the hose and are fastened by a standard screw and nut. Napa carries them.
do you have a photo of your set up that i can see?
 
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