Ok somehow my vent got clogged. Not sure how, but over time, the "hiss" when I opened the fuel cap just got massive. Knowing there was potentially going to be a need to fix it, I dumped some of my homebrew fuel down in it and doink, after 2 fillups, the hissing has gone. No more clogged fuel vent. Of course I probably have no screen on there anymore either, but for now, the ole 300D is right at 34MPG and all smooth.

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1996 E300 D
1992 300D
1990 Ford E-350 7.3 Diesel AKA "the Deep Fryer"

And what is this homebrew fuel you speak of?

Where is the fuel/air vent located?

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Pictures of the MB: http://s230.photobucket.com/albums/ee41/EricandRobyn/1981%20Mercedes/

1981 300 SD with a Goldenrod water block and Injetor line heaters. EGR is missing

1999 F-350 with HP X-over, Dahl 100 Fuel Filter, Coolant by-pass filter, CCV mod, Tymar intake.

Both on single tank WVO blend

My tank always builds up a bit of pressure when I go to refuel, never caused any problems tho..

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Ich liebe meine Autos!

1991 Mercedes-Benz 560SEL | Megasquirt MS3-Pro | 722.6 transmission w/ AMG paddles | Feind Motorsports Sway Bar | Stinger VIP Radar | AntiLaser Priority | PLX Wideband O2 | 150A Alternator | Cat Delete
1981 Mercedes-Benz 300SD | Blown engine, rebuilding someday...
1981 Mercedes-Benz 300SD | Rear ended, retired in garage.
2009 Yamaha AR230HO | Das Boot

Excessive speeding? It ain't excessive till I redline!

I heard it could eventually cause a vacume and keep fuel from getting to the engine, I dunno though.

The vent in my car is right there beside the fill neck.

As for the home brew, it is my WVO blend I run my car on. Basically about a 93% blend of WVO, 5% gasoline, and some diesel kleen cetane boost and biocide.

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1996 E300 D
1992 300D
1990 Ford E-350 7.3 Diesel AKA "the Deep Fryer"