Diesel Fuel Contamination Issues

[edgelea]

I have a '78 Series III with an 2.25l diesel that had started giving me problems. It started smoking (white/blue) on start up but would clear up when it warmed up. I chalked it up to age and wasn't to worried.This was the norm for a few months. Then it started missing and a mile later it died. I was able to restart and limp home. It behaved like a clogged filter causing fuel starvation. Changed the filter which was long overdue and it ran fine. No smoke! Well 10 miles or so after the filter change it started missing and died again. Another limp home and I dropped the filter. The bowl was full of Black Diesel which was the case the first time but I thought it was because of overdue filter change. I drained the fuel tank but the diesel there was clean. The black settles out of the fuel and seems to be oil. I changed the fuel pump in case it had been pumping oil into fuel. Any thoughts of other ways oil could be getting into the fuel system. Could the injectors let oil through into the low pressure return?

Thanks for any Ideas, Dave

[Jim-ME]

Are you getting a biodiesel blend? I've heard the biodiesel can clean stuff out live ethanol does.
Jim

[edgelea]

I have been running bio up to b50. I've been running it for over a year with no noticeable effects. If the biodiesel was breaking up gunk it seems the fuel in the tank would be showing the same symptoms. It seems to me that the fuel from the tank is clean and the low pressure return is introducing containments to the filter and then back to the distributor and injectors. Maybe those low pressure lines are breaking down.

[mechman]

Since you're running bio, it sounds like your rubber lines are breaking down. You need to change out all of your rubber fuel lines to bio compatible rubber (silicone rubber I believe). Natural rubber breaks down in bio fuel, turning into an oily goo that plugs up your system, especially your injectors.

Mech

Edit - Oil would disperse in fuel, but melted rubber wouldn't. Instead it collects in bubbles of snot like goo. If you put a ball of it between your fingers, it'll be a bit sticky. That's why flex-fuel cars are different from regular cars, it's because the hoses and gaskets are impervious to bio fuels. Another source of the rubber could be the o-rings in your diesel pump. Any rubber that comes into contact with the fuel has to be changed...

[edgelea]

When i drain the fuel filter it is a bluish black. Definitely no globs of sticky goo. I let a bit sit for a few days and it seemed to separate into diesel and what seemed to be oil. Seems like biodiesel breaking down the rubber would have happened sooner. No symptoms like this for a year.