SpeedyWS6

2006 CTD wont start. Rail pressure is ~700 cranking...and won't start. I unplugged the regulator and it bumped up to ~2000 and it will run. I checked the relief valve and it is not leaking.

I pulled the valve cover and ran the engine with the regulator unplugged and saw no signs of fuel around the injectors...

The oil is overfull but it is not my truck and he doesn't change his own oil, plus I can't smell fuel in the oil, but I have never been good at it either.

I'm leaning towards the pump... What other tests can I do? I don't want to throw parts at it.

Edit: Lift pump is working fine.

dieselfreak21

Unless the regulator is bad my guess is the injectors are shot and back flowing to much. Or the are leaking and not allowing pressure to build. How many miles and has it ever had a pressure box on it?

SpeedyWS6

~120k miles and has always been stock to my knowledge.

07 ThunderRoad

WARNING: High-pressure fuel lines deliver diesel fuel under extreme pressure from the injection pump to the fuel injectors. This may be as high as 160,000 kpa (23,206 psi) . Use extreme caution when inspecting for high-pressure fuel leaks. Inspect for high-pressure fuel leaks with a sheet of cardboard. High fuel injection pressure can cause personal injury if contact is made with the skin.

The fuel system used on the Cummins engine is an electronically controlled, Bosch HPCR (High-Pressure Common Rail) system. The HPCR system consists of five main components:

Electric Fuel Transfer (lift) Pump Located in the Fuel Tank
Fuel Pump/Gear Pump (attached to fuel injection pump)
High-Pressure Fuel Injection Pump
Fuel Injection Rail
Fuel Injectors
Also to be considered as part of the overall fuel system are:

Accelerator Pedal
Air Cleaner Housing/Element
Check Valve Banjo Fitting at Rear of Cylinder Head
Fuel Connector Tubes
Fuel Drain Manifold (passage)
Fuel Drain Valve (at filter)
Fuel Filter/Water Separator
Fuel Heater
Fuel Heater Relay
Fuel Transfer Pump Relay
Fuel Level (gauge) Sending Unit
Fuel Pressure Limiting Valve
Fuel Tank
Fuel Tank Module (containing a fuel gauge sending unit, separate fuel filter located at bottom of tank module, and fuel transfer pump)
Fuel Tank Filler/Vent Tube Assembly
Fuel Tank Filler Tube Cap
Fuel Tubes/Lines/Hoses
High-Pressure Fuel Injector Lines
In-Tank Fuel Filter (at bottom of fuel tank module)
Low-Pressure Fuel Supply Lines
Low-Pressure Fuel Return Lines
Overflow Valve
Quick-Connect Fuel Line Fittings
Accelerator Pedal Position Sensor (APPS) Located in Cab
Water Draining (maintenance)
Water-In-Fuel (WIF) Sensor
Screened Banjo Bolt (22)
The fuel injection pump supplies high pressure to the fuel rail independent of engine speed. This high pressure fuel is then accumulated in the fuel rail. High pressure fuel is constantly supplied to the injectors by the fuel rail. The Engine Control Module (ECM) controls the fueling and timing of the engine by actuating the injectors.

Fuel enters the system from the electric fuel transfer (lift) pump, which is located inside of the fuel tank and attached to the fuel tank module (the fuel transfer pump is no longer attached to the engine). Fuel is forced through the fuel filter element and then enters the Fuel Pump/Gear Pump, which is attached to the rear of the fuel injection pump. The Fuel Pump/Gear Pump is a low-pressure pump and produce pressures ranging from 551.5 kpa (80 psi) to 1241 kpa (180) psi. Fuel then enters the fuel injection pump. Low pressure fuel is then supplied to the FCA (Fuel Control Actuator).

The FCA is an electronically controlled solenoid valve. The ECM controls the amount of fuel that enters the high-pressure pumping chambers by opening and closing the FCA based on a demanded fuel pressure. The FPS (Fuel Pressure Sensor) on the fuel rail monitors the actual fuel pressure and provides it as an input to the ECM. When the actuator is opened, the maximum amount of fuel is being supplied to the fuel injection pump. Any fuel that does not enter the injection pump is directed to the overflow valve. The overflow valve regulates how much excess fuel is used for lubrication of the pump and how much is returned to the tank through the drain manifold.

Fuel entering the injection pump is pressurized to between 300-1600 bar (4351-23,206 psi) by three radial pumping chambers. The pressurized fuel is then supplied to the fuel rail.

I understand that 2000psi is all you can get out of the CP3. What I don't understand is why the ecm is trying to lower your pump pressure when the CP3 "regulator" (Fuel Control Actuator ) is plugged in. Sounds to me that the Fuel Pressure Sensor may be bad or the fuel pressure limiting valve is bad. You need a scan tool to see what the ECM is being told and what it is trying to do about the low fuel pressure. I hope this info is helpfull to you.

SpeedyWS6

ECM is stroking the solenoid in an attempt to raise fuel pressure... I think it got to 60% while cranking. Unplugging the solenoid will max it out (100%) and should give full pressure.

07 ThunderRoad

Yes it will, unless the pressure is being lost to the return or into the oil pan or loading a cylinder thru a bad injector. Also, the Fuel Control Actuator may be bad. I don't know if it can be serviced or if the CP3 needs to be replaced. I still find it odd that the truck starts with only 2000psi rail pressure. Also you said the oil level was high. How high? 1/8" over full or 1" or ? Most shops use 1gal. jugs of new oil. Kinda hard to over fill the crank case when all you have to do is pour in 2.8gal of oil and spin on the new filter (with .2gal of oil in it). I'm thinking injector dumping into cylinder or head. Good luck, hope this helps.

SpeedyWS6

I think it will end up being injectors... It is 1/2 to 3/4 of an inch overfull. I just wish I could smell the fuel in the oil. I can get it to run now so I will do a kill test on it and see what happens.

SpeedyWS6

A little update... Kill test showed #3 to be doing very little. I pulled the injectors and had them tested. All six failed.

07 ThunderRoad

Don't forget to change the oil and filters. You may want to send a fuel sample out for testing also. Dirty fuel and/or cheeeep fuel filter will kill your injectors. Is it odd to you that all 6 injectors are bad all at the same time? Find the cause befor you feed the new injectors.

SpeedyWS6

Yeah I think it is odd. But I think the cause was that the driver continued to push the truck with low rail pressure. One or two were bad first with excessive return, and that starved the rest of the injectors and burned them up.

07 ThunderRoad

Let us know of any other problems after the injectors are replaced. Thanks. This is how we all learn.

HorseBack4x4Gal

You can't do a kill test on these injectors can you? They work in Pairs I believe??

Spooler

Yes you can. With the right tool you can shut off each injector one at a time.