duramax dumping

DLOR

Well-Known Member
Joined
May 13, 2007
Location
Chapel Hill
i'll start by saying that i know very little about diesels and have never claimed to. so if some of my terms are incorrect, please be gentle.
a family friend has a chev 3500 with the duramax and it is dumping fuel, literally all over the place! i crawled under to look and the tank and two lines from it to the motor look ok. it goes up above the motor across the intake-looks ok. the fuel filter is not leaking. it looks like a terrible rear main seal leak, but it is diesel. and it is also wet across the front crossmember and along the oilpan. the intake and around the exhaust manifolds are dry. i had him turn the key on while i was under to prime the fuel pump and hopefully spray somewhere, but nothing.
is there something that i am missing? please help.
 
Also, check to see if the crankcase is full of diesel. If the injectors are bad it will fill the crankcase with fuel. The LB7 duramax are famous for this. What year is the truck?
 
hdroadkingc said:
Also, check to see if the crankcase is full of diesel. If the injectors are bad it will fill the crankcase with fuel. The LB7 duramax are famous for this. What year is the truck?
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Yup, what he said.

One of the injectors is cracked in the body of the injector, though it is possible a return line failed ( better bet is injector )

LB7 Duramax has the injectors and return lines inside the valve cover, so if there is a fuel leak , it is usually internal ( Common rail engine will not run if it can't build pressure, the odds of it leaking fuel externally and still running are pretty slim, Dmax has to build a minimum of 1450psi on engine crank )

hopefully you are under 200k miles and less than 8yrs old since initial sale of vehicle, you have a chance at special policy/warranty repair, as long as there isn't a programmer, or a tuner program hasn't been loaded into the ECM. Yes, they can tell, and are required to look at the programming to find out.

the fortunate part of this is that you now have an engine that is clean as w whistle inside, and there has been little if any damage done internally. When I was a Dmax tech, I had several trucks driven a few hundred miles like this, without issue, very messy on the bottom side and drained about 5gal of oil/fuel from the engine.
 
Oh, and the fuel is venting from the draft tube that vents just below the engine on Pass side front if I remember right.
 
i didn't even think about checking the oil. it does run fine, just drips a tons of fuel. not sure of the year, but it is the 02-07 body style with no mods. so does new fuel injectors and an oil change fix this?
 
DLOR said:
i didn't even think about checking the oil. it does run fine, just drips a tons of fuel. not sure of the year, but it is the 02-07 body style with no mods. so does new fuel injectors and an oil change fix this?
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Essentially, yes, but there is a certain amount of diag that needs to be done to be sure what the cause is.

just "changing the injectors" isn't something one with little diesel experiance should try and attempt. there are a few special tools involved, and a lot of "gotcha's" that can make you have a really bad day.

LB7 injectors sit in an injector cup in the head, when you pull the injector, many times the cup comes with the injector, and needs to be properly seated and sealed. and if you haven't drained the coolant and pull these cups, you have just filled that cylinder with coolant. 'O' ring seals, crush washers, banjo gaskets, hell, just puling the valve cover and lower valve cover can be frustraiting with out the proper tools.
 
i just googled it and i think he has a warranty claim. it looks like a pain and like you said special tools required. without very much diesel knowledge, i'll point him in the dealer direction
thanks for the great info/help.
 
clarification (after the fact)

hdroadkingc said:
A duramax dont have a fuel pump, so turning the key on wont spray fuel like a fuel injection car with a leak. Will it run?
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it does have (2) pumps - a lift pump and an injection pump. both could possibly spray fuel.
 
Hurley said:
it does have (2) pumps - a lift pump and an injection pump. both could possibly spray fuel.
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injection pump yes, lift pump, only if it was added after the fact. the newer trucks LMM/LBZ may have lift pumps, I have very little experiance with those, I left the dealer just before they were released. Trucks with dual tanks do have a transfer pump, but thats tank to tank.

Injection pump SUCKS the fuel from the tank by design, and then pressurizes the fuel in the fuel rails and injector lines.

So if you don't get the fuel filter seated, or a pin hole in a fuel line, you ain't getting fuel.

I have seen an LB7 injection pump frag, push out the plugs in the body of the pump and STILL run well enough to drive it into the bay, we were all quite amazed by this, fuel dumping out running down the valley and to the ground, and the engine was still running.
 
Dont know about the LMMs but my dads LBZ only has the injection pump, no lift pump. His started leaking fuel from the drain on the bottom of the filter and it ran all over the crossmember and right frame rail and it got hard to start cause it was loosing prime.
 
voodoo is dead on. Its prob injectors or return lines. however the warranty is 200k/7yrs since it left the lot not 8.
 
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