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Discussion Starter #1
I'm pretty new to working on this engine and have had a tough time narrowing down a diesel leak on my 86 6.2L. The leak is pretty significant after running the engine about 20mins, but doesn't leak when off. Also my truck has been hard starting since that leak appeared. Only method I've found to get it started is to bleed the fuel filter assembly, then it starts right up...To that end, I'm also now in need of the top bleed valve on the fuel filter as mine was sheared off at the top of the threads and is getting to be a pain to remove and tighten each time I need to start it. (I haven't had any luck locating one at local salvage yards, so If anyone has an extra lying around you'd like to part with let me know)...Any advice on narrowing down this leak that anyone could provide is appreciated. Thanks, Robert.
 

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Well, leaks can be interesting if you can not see any fuel. I assume you don't see any fuel. Possibilites: return fuel hoses(going from injector to injector) or caps on back 2 injectors, injection pump(probably not), mechanical fuel pump check valve leaking by(draining fuel back towards tank) to name a few. I would start by locating any fuel residue first. Good luck

Matt
 

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Fuel leak is probably in the engine valley, probably the fuel line that goes from filter to injection pump. Clean everything off very well and then with mirror and flashlight in hand, find where the fuel is leaking from. When all else fails, pressurize fuel tank with about 3 psi of air and check for leaks. Remember, your truck is over 20 years old, rubber lines are probably cracked and deteriorated.
 

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Ditto what Dave said. Remember, a diesel fuel system is like a soda straw. If you pull soda up into the straw and put your finger over it, the straw will stay full. If you have a pinhole in the straw, the straw will "leak down" even with your finger sealing the upper end.

The fuel system is the same. Any "leaks" in the supply side, the fuel bleeds back to the tank, leaving the pump supply dry. Usually, if the pump is sealed up well, the engine will start, run a few seconds and die when the air in the systen hits the pump. If it won't even try to start and run, after sitting, it could be the throttle shaft seals or the advance piston cam pin seal in the IP.
 

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Discussion Starter #5
Appreciate all the help. I won't have a chance to really dig into it until early next week, so I'll let you all know how it goes. Turns out now my starter has also decided to go out, so I'll have to fix that before tackling the leak. It's been an expensive month for the ol' truck. Rebuilt TH400, New tires, Starter work, diesel leak,...Next month should be cheaper (I hope :eek::) . Thanks again for all the tips. -Robert
 
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