02 duramax fuel leaking out of bell housing

[diesel derrick]

02 Duramax leaking fuel from bell housing doesn't smoke or start hard runs a little rough is it the injectors or the pump

[rapidoxidationman]

Whats your oil level is it still oil or is it mostly diesel leaking injectors might want to check your oil it would suck to hydrolock your engine from too much fluid in the crankcase

[diesel derrick]

Mostly diesel

[Kennedy]

A leak in the valley will drain to the rear making it run down on the bellhousing.

[diesel derrick]

I have taken the valve covers off is there any way to pressurize the fuel lines to see where it leaks

[DmaxMaverick]

I have taken the valve covers off is there any way to pressurize the fuel lines to see where it leaks

Not sure why you removed the valve covers. If you have a leak there, the fuel will drain into the crankcase. If the leak is significant, it will overfill the crankcase, and the oil/fuel mix will blow out the crankcase vent tube at the bottom/front of the engine (and cover the entire underside of the truck, bumper and tailgate in a short time), NOT the bell housing. Fuel-contaminated engine oil will usually cause a significant drop in oil pressure, as well as rough running, and eventually, the messy overfill condition.

As John said, a leak in the valley area will drain onto the bell housing. A possible source will be between the high pressure pump and the injector lines, or a fuel return line (low pressure), OUTSIDE the valve cover. Look at the pump, pressure regulators, HP fuel rail and line connections. The fuel system is purely suction from the tank to the HP fuel pump in the engine valley, so unless you have installed a fuel lift pump, an external leak before the HP pump is very unlikely, and would be very slight if it did.

[diesel derrick]

It was blowing out the breather tube and overflowing im guessing out of the rear seal there was no evidence of a leak around pump. Im going to remove injectors tonight will it be obvious if one of them cracked? Sorry for lack of information on previous threads

[DmaxMaverick]

You won't "see" a crack, on a cracked injector, almost never.

If you are getting a lot of fuel into the crankcase, check the return lines before pulling the injectors. The return lines can crack, and the seals can leak. You can (low) pressurize the return lines at the outlet before removal. Even a few feet of gravity pressure is all that's needed, and a leak should be obvious. Clean the area well, apply low fuel pressure, and watch for fuel wetness over a period of time (blot with a white paper towel). If the returns don't leak, then you have bad injector(s). To high-pressure test the injectors, you'll need a Bosch test bench (good luck finding one outside a reman facility). There's no reason to pull an injector without full intent to replace it (or replace/reseal a sleeve). Removing the high pressure pipes alone has likely contaminated at least some of them.

[diesel derrick]

ok I've finally gotten to the bottom of the valve cover. I plumbed all the fuel lines back in and cranked the motor over NO obvious leaks. I dried all return lines and stuffed paper towel around them to see if I can catch a leak. But its looking like injectors any other suggestions.:confused:

[DmaxMaverick]

If it didn't fire, there was no (or too little) fuel pressure, at either end. Cranking the engine would only rotate the pump, but may not produce any pressure. It won't, until it's ready to start. If you were able to crank it, and it didn't start, there was no fuel.

[Kennedy]

Removing the injector lines on the LB7 is a crap shoot. In most cases it introduces tons of rusty grit to the inlet of the injectors:

http://www.kennedydiesel.com/docs/Duramax%20LB7%20Injector%20Line%20Corrosion.pdf


If you are looking for leaks good luck finding them w/o a black light and tracer dye. Ideally what you would do is start up and use a Tech 2 to command the rail psi up.