Will a fuel return leak cause a major power loss?

Detroit80

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Truck is a '96 K2500 4x4 220K miles, stock other than relocated PMD and homebrew turbo-master style wastegate controller, set to max of 12psi. Runs smooth, occasionally have to crank it a bit to get it started, but nothing that I'd consider major. No stalling issues or feeling like it's missing.

I've had the common fuel leaking off the bell housing issue on and off for a while. Some times it seemed to go weeks without an issue, then suddenly I'd come out of the store and find a massive puddle of diesel under the truck, then it would be fine for a while again. I raised the filter manager up above the intake, replaced feed hose and hoses to bleed valve and IP.

A couple months ago I went a couple hours out of town to pick up a car. Between car and trailer weight, I had about 6K pounds on the hitch. On the way home it suddenly had a massive power loss...it would barely do 55mph foot to the floor, wasn't building more than a few pounds of boost, but also wasn't setting any codes so it wasn't like I just overboosted and set the defuel code (using Torque Pro on the phone with the extra 6.5 PIDs loaded, so it will show that _a_ code was set, without it showing up in the normal code scan list). Tried clearing codes a few times anyways..didn't do anything. It's felt way down on power ever since.

I've since noticed the fuel leak has gotten MUCH worse, to the point that it's almost a constant stream of fuel leaking off the bellhousing, but I can't find the source of the leak. I pulled the upper plenum to check the IP and lines - they're dry. The only thing I can think of it being now is the return line behind engine/top of bellhousing. I also noticed a massive amount of vapor coming out of the CDR hose when running with the plenum removed.

So now I'm wondering if I should tear into it more to dig out that return hose and replace it, or if I'm more likely just dealing with a very tired engine? I'm tempted to take the trans and interior for my other truck and part out the rest...
 

Detroit80

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Yes...turned out to be two leaks - optical sensor o-ring was weeping, and the weep hole at the bottom was dribbling fuel. After replacing the o-ring, it started pouring fuel out the weep hole, at which point I called it quits, lol. Ended up yanking the trans out of the truck to replace the blown trans in my K5, and the truck has been parked since.

I've got a ton of other higher priority projects on my plate right now, but I do plan on eventually building a whole new trans for the K5, as the BBC in it now makes more power than a stock 4L80E can handle, then swapping this trans back into the truck with a new injection pump...eventually...
 

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