Bosch VP44 injection pumps perform four basic functions:
1 - Producing the high fuel pressure required for injection
2 - Metering the exact amount of fuel for each injection cycle
3 - Distributing the high-pressure, metered fuel to each cylinder at the precise time
4 - Varying the timing relative to engine speed.
The Bosch VP44 is an electronic rotary distributor pump that can vary fuelling and injection timing, and also contains fuelling, timing, and diagnostic data.
The following are the top two most common mechanical failures:
1 - Rotor Seizure Another mechanical failure with the Bosch VP44 injection pump happens when the rotor seizes in the distributor section of the pump. The most common cause for the seizure is a lack of lubrication. Since the Bosch VP44 injection pumps are lubricated by the fuel, weak lifts pumps can again be blamed for this failure. The seizure will then break the Drive Plate and the truck will stop running, never to start again, until the Bosch VP44 injection pump is replaced.
2 - Check Engine Code 216 This is the most common mechanical failure and occurs over a period of time when weak lift pumps, with low fuel pressure, rupture the diaphragm in the front of the injection pump. The timing piston will then vibrate to a point where it wears the housing of the pump down until the fuel is able to bypass the piston. Dodge has recognized this problem for some time, and they no longer even sell the lift pump that goes on the side of the block anymore, instead they replace it with a unit that is now mounted in the tank.
Overall the number one cause of Bosch VP44 injection pump failure is a drop in fuel line pressure which is usually due to a malfunctioning lift pump. Normal fuel pressure is around 15psi and if the pressure drops below 5psi an injection pump failure is probable. Remember bad lift pumps can run unnoticed until costly damage is done to the Bosch VP44 injection pump.
Preventing Bosch VP44 injection pump Failure The best way to avoid failures of the Bosch VP44 injection pump is to prevent them from happening. Purchasing a replacement lift pump, one that is of a better quality than what comes from the factory will help. If that option is too costly, you can also install a gauge to monitor your fuel pressure. With the gauge you will be able to know when your lift pump is going out and can easily fix the problem before you lose the Bosch VP44 injection pump.