Ineffective flush procedure...

lmorris · October 5, 2016

Starting up a new thread because this is the first time I have run into this situation. I have done a few contaminated fuel system repairs, mostly gasoline or metal in the system. Only 2 for DEF. The first one went smooth, I don't think the truck was actually ran, but the key was turned on. This current one was ran. I removed the tank and cleaned it out. Performed the flush procedure per the GSB, removing the fuel cooler inlet line as stated. This was my mistake, I didn't take into consideration how much DEF might have been in the system because the customer said they had drained the tank themselves, but it still runs rough. After getting it all fixed up and running the water in fuel message pops up. Pulled the tank again and its definitely got more than just diesel in it. My thought is the rest of the return system from the fuel cooler back was full of this crap and was pumped back into the tank. Thankfully the separator caught it and nothing made it to the engine. Now that it's back together a second time, I have removed the return line off the pump and have run a few more gallons through it.

Anybody else have this happen?

Matt Saunoras · October 6, 2016

I'll start by saying I have only done one DEF contaminated fuel system and its unlikely i'll ever work on that truck again.

I do not like the GSB flush procedure for heavily contaminated systems. I interpreted it the same way you did. For retail jobs I replace the fuel cooler and I am also blowing out each individual line with compressed air and brake clean. For warranty purposes with only metal contamination the flush is probably not as important, I know Fords thinking is the filters will catch any remaining metal.

RyanG · October 6, 2016

I don't follow the gsb either. If its had def go through it, I put a fuel cooler for customer pay. I flush all return lines and blow them out. If there is metal in the tank, I drag a magnet through it until I get all the metal I can then flush it with water and dry it out.

Steve Mutter · October 8, 2016

I agree, I don't like the way the gsb has you flush and does not have you replace the fuel cooler. I removed all the frame mounted lines and flush them out individually. Leaves no doubt that things are %100 clean.