I've got a 1987 300D. I recently had a fuel gelling incident. So I changed both my filters. I've also replaced all my remaining rubber fuel lines with clear polyurethane lines. I run 100% biodiesel. So I treated my fuel tank with an anti-gel agent. I can see the fuel (and air) in all my lines since they are translucent. There is no air coming through the prefilter and up to the secondary filter. The fuel coming out of the secondary filter is full of air.

Here's how it happened: I changed the filters and lines the night of the gelling incident, got the car primed and running fine. Let it run for at least 15 minutes, warmed it up, drove around the block. All is fine. Fuel coming from the tank looks clear, and not cloudy. Shut it down, plugged in my block heater and went to bed. Next morning I open the hood, the car starts fine, and as I watch, a little bit of air starts getting in the supply and return lines, it gets worse and worse over the course of a minute or two, until the car is ready to stall. The air problem starts at the exiting line of the secondary filter. The filter is tightly screwed on, I replaced the o-rings on the center bolt (anyone know what the torque spec is for this bolt?). The filter is new.

Any ideas?

Thanks!

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1987 Mercedes 300D ~200K (Greasecar & Biodiesel)
1993 Ford F-250 7.3 IDI diesel 165K (Biodiesel)
1996 Thomas/International Bus with DT466 engine

Shouldn't there be a crush washer under the filter bolt?

Sixto
87 300D

i think some do some don't if i recall? i remember u can sometimes find a leak by hooking a air hose up to one end and really low pressure 5-10psi or so listen and look for a leak might help?

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2004 Infiniti G35 3.5L 6mt Coupe 73K miles 25.6mpg ytd
2001 Green Audi TT 225 AWD Roadster 71K 6sp 30.9mpg >>STOLEN<<
1982 300D Turbo 231K 120hp? 28.1mpg YTD

Sure enough - it appears the crush washer on the banjo bolt is pretty well "crushed". I think that is the likely culprit. I'll have to wait until Monday to find a place that will carry a replacement. My banjo bolt is also a bit stripped, so I'll likely have to go to the dealer.

When using a crush washer, which side is supposed to mate with the bolt, and which side mates with the metal housing you are threading into?

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1987 Mercedes 300D ~200K (Greasecar & Biodiesel)
1993 Ford F-250 7.3 IDI diesel 165K (Biodiesel)
1996 Thomas/International Bus with DT466 engine

I use plain old washers. Aluminum or copper. Not the kind that's a hollow section that's flat on one side and round on the other.

Sixto
87 300D