Stock Lift Pump / Cummins Campaign Pump
There are some serious design flaws in the stock fuel system. The stock lift pump or the Cummins Campaign pumps are both unable to supply enough fuel volume for a hungry Bosch VP44 injection pump. Part of the problem is the stock lift pump is only good for 35 GPH flow rate. However, even Bosch states that the Bosch VP44 injection pump needs at lets 70% of the fuel return to the fuel tank which is used for cooling and lubing the Bosch VP44 injection pump. So how much fuel does the Bosch VP44 injection pump consume at a WOT run? For a stock truck, you could see as high as 18-20 GPH. Now let's do some simple math. 35 GPH - 20 GPH = 15 GPH... Then 15 GPH / 35 GPH = 42% being return to the tank roughly. This is one point of failure with stock lift pumps.
This last picture shows the plastic hub that normally starts to slip or breaks this is why I tell people it doesn't matter if the pump makes noise because the motor might be turning, but the pump rotor is no longer spinning. Now the other failure like this is the plastic will start to slip and pressure falls as friction builds up the plastic will melt and bond again, and the pressure rises once more. This what caused the pump above to fail was slippage of the rotor.
As for the pressure regulator, I don't have a picture of this, but if you look inside the ports of the lift pump sometimes you can see the spring and check ball (BB) inside one of the ports. This body of the pump is nothing more than pot metal (cast aluminium) which the check ball rattles against the seat of the aluminium until the check ball is leaking pressure back around itself so the pump goes into constant recirculation.
The Cummins Campaign Pump is a redesigned lift pump for Cummins’ engines. It was originally designed for the Buses. The campaign pump is identical to the Dodge OEM pump, which is supplied at manufacture, yet is much cheaper in price! Unfortunately, the Campaign pump is no longer available. The ones that are attainable are very expensive; due to demand, but the part number is 4090046 if you want to take your chances.
Lift Pump FAQ's
Q: What is the voltage to the lift supposed to be?
A: Lift pump should have a constant 12 Volt supplied to it while the engine is running. During cranking the lift pump voltage is modulated 50% duty cycle to reduce starting pressure.
Q: What's a stock lift pump pressure supposed to be?
A: Normally, a good lift pump should be about 14-15 at idle and about 11-12 PSI at wide open throttle at 65 MPH.
Q: What is the lowest lift pump fuel pressure allowed?
A: No lower than 10 PSI as stated by Dodge and Cummins both. Below this pressure, Bosch VP44 injection pump damage will result.
Q: How much volume does a stock lift pump provide?
A: Approximately, 35 GPH
Q: Is the fuel pump relay in the power distribution center the relay for the lift pump?
A: No. This relay is the power supply relay for the Bosch VP44 injection pump. The lift pump has no relays and is directly controlled by the ECM.
Q: How long will a stock lift pump last?
A: I've seen a little at 10,000 miles, and some have reported as far 100,000 miles. However, at any rate, I would still have a fuel pressure gauge to monitor the lift pump health.