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Have a 2003 6.6 Duramax, and when I step into the fuel pedal to make it down shift into passing gear, it does downshift, but then the fuel pedal goes dead, it will not rev higher than 2000 rpm, and if I hold it down, it brings up code P00087, Fuel Rail System Pressure Too Low, and will smoke until we let up. This problem has been dogging this truck for just about a year. The dealership replaced all injectors, fuel pump, countless fuel filters, fuel tank, all new fuel lines (except for the fuel cooler rad on the frame), and now, tonight, we changed the fuel temperature sensor. No change! We are at a loss here. Hoping someone out there has an idea on what might be causing our headaches. Am posting this for a friend, and until this year, this truck has been bulletproof.
 

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hook up a scan tool and post your results..ex balance rates, rail pres acc vs des....could be a weak cp3...tsb on it tho...this could be your problem
Subject: Diesel Engine Fuel Line Repairs


Models: 2001-2007 Chevrolet Silverado Classic

2001-2007 GMC Sierra Classic

2007-2009 Chevrolet Silverado

2007-2009 GMC Sierra

Equipped with the 6.6L Diesel Engine RPO codes LB7 LBZ LLY LMM




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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A dealer may need to perform a repair on the rubber portion of the fuel supply (suction) lines. The rubber section of the line could become kinked or collapse. Fuel lines that kink or collapse may induce a fuel system restriction (high vacuum gauge readings) or DTCs P0087, P0093, and/or P1093 to set.

If a technician was to suspect the rubber portion of the fuel feed line collapsing or kinking, replacement of only the rubber line is acceptable.

Recommendation/Instructions:
Complete the steps below to repair the rubber section of fuel supply line:

•Carefully cut, split, and remove the OEM crimp from both ends of the flexible hose. These crimps can be cut with a small cut-off wheel. Split the crimp into two pieces (use your discretion on first cut location, then cut directly across from, or 180 degrees from first cut). Special care must be taken not to damage the flare on the end of the steel pipe that will be reused.
•Remove the OEM crimps and flexible portion of hose from the existing supply line.
•If replacing the rubber section of the supply line, a 1/2 ID hose meeting SAE specification 100R3 is suggested. Dealers may be able to find a local supplier for this hose, or can contact the manufacturer Parker Hannifin. The replacement hose would be a 1/2" diameter Parker part number 601-8 or H017-8. To find a local distributor the Parker website can be accessed at Please wait while we redirect...
•Use worm type hose clamps (use double clamps on each end) to attach the replacement hose to the existing pipe.
The locations of the flexible hoses are pictured below.





Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
 

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The locations of the flexible hoses are pictured below.
Do you have the pictures of where the rubber fuel lines are located in the repair description? We replaced the metal lines from tank to engine, but are sure that there are rubber lines located on the engine that were not replaced and might be collapsing.

BTW, Thanks for the reply!!
 

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My 07 Gmc has the same problem. Replaced 8 injectors fuel filter all rubber hoses on fuel lines. Dealer did a presser test and said nothing showed up. I have an edge programmer installed on the truck. Truck got better fuel mileage on tow mode but when I get on, it goes into limo mode. I bought a fuel rail race plug but have not installed it yet. I get 20 plus when not towing. Every time I take it into shop they tell me everything checks out fine. But it cost at least 100 dollars or better.
 
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