Mystery fuel leak

[ByronRACE]

I'm having difficulty locating the source of a fuel leak. My fuel filter area is bone dry everywhere, including the electrical plug area and top seams. My injection pump area is bone dry. However, the area between them; starting high on the block just below the head is wet...and it drips down the side of the block. And, it doesn't leak at idle, or neutral revving. It leaks only going down the road.

I've de-greased and dried the area twice...it's always wet in the same spot.

I don't see any fuel fittings in that area...am I missing one? Do these lines ever develop holes? I'm in CA; rust is not likely...but what about friction-induced holes in the lines? I see a small return line against the block in that area...could that have rubbed through?

Any ideas? This is hard to find.

[RCCUMMINS89]

Have you checked your afc vent tube?

Otherwise there is a connection in between the two on the fuel supply line, but it should leak while revving.
Which leads me to believe that it may be your afc leaking. They'll commonly only leak when under boost.

What fuel pin are you running?

[CumminsPower59]

Im guessing its either the feed line or return. Both run in that area that you talk about.

[ByronRACE]

AFC vent tube is dry. The wet spot up high on the block is about a foot behind that, half way between there and the fuel pump.

I see a tube fitting up in there on the feed line between the fuel pump and the injection pump. That's very near where the block is wet. I wonder if that thing is spraying when the pump gets running at a higher rate...but it should leak if I neutral rev it shouldn't it? Does that little return line carry more fuel when under a load? Why is there a return line there, what does it do?

I'll dig back into it after the rains stop. Until then, I'm working on fabbing up my down pipe and exhaust brake inside the nice dry garage.

[CumminsPower59]

I see a tube fitting up in there on the feed line between the fuel pump and the injection pump. That's very near where the block is wet.

Im guessing its the feed line.

[ByronRACE]

Found it finally.

The fuel return line Tee at the back of the head on the drivers side was squirting a nearly invisible stream of fuel back toward the fuel filter area and spraying the side of the block; but only sometimes; and only when being driven under load at freeway speeds.

I took this tee apart and found the line coming from the injection pump had a hairline crack under the compression nut.

I sanded the line clean and scrubbed it down with acetone, then silver soldered it, sanded it smooth, and reassembled. I just got back from driving it; and it's dry. I would say the problem has been solved.

[dazedandconfused]

Good deal.

[CumminsPower59]

Awesome!