First a little background: I am getting ready for a vegetable oil conversion on this thing, and am in college so when I go home I do a few hours work on it and then have to pack up, and work on it again a few weeks later. Slow progress. I have replaced the banjo bolt on top of the fuel filter with a solid bolt, and just this weekend I replumbed the system so that the lift pump pulls fuel through the fuel filter and a fuel supply solenoid, and returns through another solenoid (high quality Frybrid 3 ways). As expected, it ran rough, so I tightened hose clamps, and snugged down banjo fittings (although I didn't have any new crush washers - I'll have to get some). It ran better, but then I did a long overdue fuel filter change and it was back to normal.

Then I took off for college, and ran out of fuel less than a mile down the road. I guess that reserve fuel light isn't lighting anymore. I got some diesel, cracked the injection pump supply fitting, and pumped till I got good flow. She started up and ran great. But then wierd things started happening.

Throughout the whole trip, when I would slow down to idle, it would run just a tiny bit rough sometimes. Then when I'd start going, I wouldn't have full power, although I'd still acclerate, just slowly. I'd keep it flat to the floor, and it would pick up like normal all of the sudden and go great. It would run great until I stopped again, and half the time when accelerating it would do the same thing, acting like I had a small air leak.

I don't think this is a regular air leak, because the problem goes away when I get to a higher speed, and sometimes doesn't happen at all. Could I possibly have a big air bubble in my fuel filter, from running out, that I keep getting pieces of (but then, why would it show up at idle)? I may take the banjo off the top of the fuel filter, and pour a little fuel in to make sure it is totally full, no air. Any other ideas?

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1985 300D, 237k.
1994 F-350, 6.9 diesel, 5 spd manual, Banks Turbo. 261k.
Sold: 1985 300CD- 267K

When you replaced that bolt and re plumbed the system you eliminated the stock design that allows the car to vent air from the fuel system. I believe your theory is correct, you have a air bubble in your main filter. I had my SVO conversion plumbed the same way and could barely get the thing to prime. I was going to change my routing back to the stock configuration and put the fuel supply valve just before the injection pump. I was then going to use a 12 V pump for the oil side of the system. Now I am selling my conversion...tired of grease in my trunk.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine