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Discussion Starter #1
I currently have a 2004 Chevy 2500hd with the lb7 in it, I bought the truck knowing the injectors had been done on it by the previous owner I drove the truck for a while with no issues then i had a fuel leak on the cooler for the fuel so I got the air dog lift pump while I was under there I deleted the cooler, fast forward I’m driving on the highway and notice the oil pressure is dropping pretty low and that there is diesel in my fuel. I have no hazing no white smoke true fires right up no problem I’m thinking it maybe a return line leak? I’m kind of at a loss here and thought maybe someone on this forum could help thanks!
 

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Discussion Starter #2
I currently have a 2004 Chevy 2500hd with the lb7 in it, I bought the truck knowing the injectors had been done on it by the previous owner I drove the truck for a while with no issues then i had a fuel leak on the cooler for the fuel so I got the air dog lift pump while I was under there I deleted the cooler, fast forward I’m driving on the highway and notice the oil pressure is dropping pretty low and that there is diesel in my fuel. I have no hazing no white smoke true fires right up no problem I’m thinking it maybe a return line leak? I’m kind of at a loss here and thought maybe someone on this forum could help thanks!
Sorry I meant diesel in my oil 😓
 

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Sounds like you have a cracked (leaking) injector body or line. If the truck is making oil (leaking fuel into the crankcase), then you shouldn't drive it like this for long. How long ago where they replaced? Could be as simple as a bad banjo seal. I would drain the oil pan and see how much fuel/oil comes out. Diesel fuel in the oil is no bueno for an engine.
 

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Discussion Starter #7
Another thing I noticed here in the shop is the cp3 maybe leaking? I have diesel all over the cat filter that was installed by them as well..
 

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Another thing I noticed here in the shop is the cp3 maybe leaking? I have diesel all over the cat filter that was installed by them as well..
Is this filter on the primer filter "hat"? Did they install an adapter for that filter? If its leaking there, the primer hat most likely has a leaking O ring, or one of the two fuel lines that connect to it have a loos clamp, or the lines are bad. Common area in the fuel system that needs attention after age.
 

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Yes that’s correct another thing I guess I’ll address while I’m in there, went out this morning And drained the oil definitely has a diesel smell to fit gonna try and run it without the valve covers on, isn’t there a die I can purchase that will show where the leak is coming from? Old lady’s telling me to just upgrade it 😂😂 some hours labor and a few busted knuckles is definitely better than a mortgage on a truck!
 

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Might cost a little more but depending on how many miles you on the oil change and the amount gained.. might look into getting new return lines that go inside the vavle coversbif you can't find it with the vavle covers off. Also make sure you unplug the FPR so it gives it max pressure on it to help find the leak. Finished the whole works on mine, minus exhaust leak, last night. Any questions feel free to message me with.
 

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I am having the same problem. its an 03, I rebuilt the engine a couple months ago. Truck runs great besides 4.5 gallons of oil. I sent the injectors out for flow testing and to make sure they were not cracked. New feed lines, new return lines, new banjo bolts and washers for return lines. Injectors are Industrial Injection 30% overs with 65k miles on them and they all tested within a 4cc variance. Balance rates are within spec. I have added UV fuel dye and checked the CP3 seal for leakaged with the oil fill neck removed. I have sent compressed air through the return to take or in my case lift pump with no obstructions found. The truck has been ran with the valve covers off before the UV dye was added. No leaks found. Also replaced all copper washers and injector body O-rings. New O-rings on all injector cups and loctite. Everything has been torqued to spec per Hanes manual and Identifix. I had all my money on a leaking CP3 front shaft seal. With the rail pressure cranked up to 23,000 PSI via Tech 2, no fuel spray out of the seal on the Front of the CP3. Unpluged FPR as well to see if CP3 was leaking before I got my hands on a Tech 2. I have been through hundredes of forums and tried everything under the sun.... At a complete loss.... Any other ideas? Truck has 300k miles on it, freshly built engine less than 5k miles. CP3 has 300k miles as far as I know. Desired rail pressure and actual are almost perfect. within 100-200 psi. EVERYTHING was built within SPECS of the Hanes manual and Identifix. Everyone says replace injectors, feed lines, return lines, banjo bolts, banjo washers,O-rings and It will fix it. Don't see any problems with any of them. Please help I am at my absolute whits end with this money pit.
 
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