On my 99 F450, I had to replace the fuel lines that run up the drivers side of the engine to the filter housing, I could not get the quick connect for the larger line to come loose, I ended up putting it all back together, driving my truck puking fuel to my mechanics shop, taking it all back apart again and having the mechanics all take a turn at trying to get the #@&^% quick connect on the larger feed line to come loose, they tried 5 different tools on it, and we all took a turn, then the 4th mechanic after 40 minutes of everyone trying was under the truck for maybe a minute, hopped back out and said it's off.
10 minutes later it was all back together with the new lines installed and the truck running.

I found out that the lines have a bracket on them that is supposed to be bolted to the block just above where the ground attaches on the drivers side, just below where the water pump outlet is. MAKE SURE THAT BOLT IS TIGHT, the lines cost me 105 from FORD, using my mechanics account, list is over 130bucks. I could see a hole in the old line where it had vibrated and rubbed against a small plug in the side of the bottom of the block. I found a bolt for the hole and tightened it down. I will be checking that on both of my 7.3 at every oil change now..

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The hole closed some when I pulled the tubing out and it twisted and bent some.
I was surprised that the truck still ran fine with that big of a hole in the feed line. My mileage was down 1-2 mpg which when your only getting 10 at best is a lot. (I "used" a little over a 1/8th tank of fuel just driving 30 miles from work, to the dealer and then home.

I am not sure how long that hole has been in the line, I know it got progressively worse though, My truck has always had a small oil leak, that is not bad enough for me to change out the LPOP yet, I wonder how much of the "oil" that I was seeing was really diesel mixed with the oil that was dripping off the cross member. It was really bad there towards the end. If you tried hard enough you could have followed me home just from the diesel trail.

I checked my mileage today, and for the first time ever the truck got better then 12, it got 12.86 mpg, that was towing my trailer the entire time too. SWEET!

 

Good find Donn. We should add this check to the Failure Prevention Thread

Might also consider adding the part numbers for others who may be searching for these failures.

The P/N's for the hard lines(Feed and Return) on the motor are F81Z9J338NA around $130.



And for further reference the flex lines are P/N 2C3Z9J338BA, like $175 MSRP though, I might consider just installing 30R9 fuel line personally.

 

I wish the fuel lines I got from the dealer were nice and shiny like that, they were rusty as heck, only 1 dealer in town had the lines, and being that it was the one that my buddy has his account at, I ran some WD through them and blew it out just to be sure there wasn't anything inside them before I threw them on. I had began to wonder how far back the flex lines went on the truck. There was a point that if the last mechanic had not popped the QC loose I was going to cut the hard line and pull the tubing off at the pump and pull the whole thing out so I could work on it on the bench. If it still didn't come apart I was going to use fuel hose and some clamps. Glad it didn't come to it...

 

Hey almost 13 mpg-I would say that is great mileage. Your truck being a 450 and specialty bed probably weighs in excess of 12k empty and with a 4.88 rear end. My truck has 3.73 and weighs very close to 8250. I can get 17 plus empty going to Denver. Pulling my LQ horse trailer I get a little better than 10 with the DP.