This morning I walked into my garage and smelled raw diesel. Looked under my truck and saw a small puddle of liquid...stuck my hand in it and smelled....it was fuel.

I got under and looked....the starter was wet, as were the tranny lines directly under the starter and the exhaust cross over tube.

I pulled the truck out ( started fine ) and let it idle in the driveway while I wipped up the mess. I let it idle for at least 10 minutes...no leakes.

I took it for a drive - about 10 miles or so. Backed it back in the garage and crawled under....no leakes.

I let it sit in the garage for a couple hours...I just went back out and damn it all there is FUEL UNDER THE TRUCK AGAIN. Starter is wet again....so are the tranny lines and exhaust crossover.

I wipped up the mess and started it again and let it idle....i couldn't find anything.

I checked the fuel filter and the drain....all looks clean...besides it is too far forward in the engine bay to drip in this area.

Any clues?

 

Check the valley pan.
The drain for the valley pan exits through the rear of the engine.
Any fluid in the valley pan drains out there.

Also check the bottom of the IP and all the lines on the engine for leaks, both running and right after you shut it off.

How much fuel would you say was on the floor?

 

Just got back from under the hood. I now see how leaks can be directed back toward the rear of the engine.

The valley pan for the most part is dry....and pretty darn clean for being 17 years old...just a slight flim of oily mess on it. The IP looks to be fine. Directly under it is as the rest of the valley pan is....dry but with a slight film. All fuel lines ( steel and rubber ) appear to be DRY with no oil, film, goo grease etc. Lines and the clamps between each injector are dry. There is one line I can not get to. It is the line that runs between the rear injectors. It loops under what I think is the cdr valve ( as mentioned in this thread ( https://www.ford-trucks.com/forums/6...he-diesel.html ). One injector ( second from the front on the drivers side ) area looks "damp"....actually the injector is dry itself, the glow plug and surrounding area is slightly greasy looking. It is not wet enough to create any type of flow that would cause a drip.

The amount of fuel on the floor created a wet spot about 10" in diameter.

The valley pan under the cdr valve does have a good amount of grime on it but there is very little visibility...tough to see.

What is bugging me is why is it leaking only after it sits for a good amount of time?

 

I was able to get it to leak again....after idiling for several minuts in my driveway , I backed it back into the garage and shut her down. This time it only dripped enough to create a wet spot of 2" diameter...5-6 dripps tops.

But there was nothing in the driveway and it didn't leak until I left the gargage for 15-20 minutes or maybe more.

 

Check the metal supply line from the tank selector valve to the fuel lift pump.

On my 86 I know it crosses there somewhere and then runs up inside the frame to the lift pump.
Actually I think it is on the rear of the crossmember, but that is still close enough to be your problem.
If there was a leak in the supply line, it is letting air into the line when the engine is running, so no leak.
After the engine stops, leak because that line is lower than you fuel tank.

A 10" diameter spot on concrete is a rather small leak, but if it is in the supply line it will get worse and leave you stranded at some point in the near future.