VD44 Injection Pump Problems

The fuel injection pump (VP44) is an electronic rotary distributor pump. The pump performs four basic functions. It first produces the high fuel pressure required for fuel injection. The pump also meters the exact amount of fuel for each injection cycle. As the diesel fuel moves through the VP44 it is distributing the high-pressure, metered fuel to each cylinder at the precise time. The fuel pump then varies the timing relative to your Cummins engine speed.

What caused my VP44 pump to fail? How common are VP44 injection pump problems?

The most common cause of VP44 failure is to lack of fuel. Dodge trucks 98.5 and up are notorious for having weak lift pumps. Unlike most injection pumps the VP44 is fuel cooled and lubricated. Therefore, if its fuel supply comes from a weak lift pump, it is very easy for the VP44 to overheat and cause damage to itself. This lack of fuel results in one of two types of failure within the VP44. One is that the diaphragm inside of the pump is damaged and does not allow the pump to build up the appropriate amount of pressure. The second is that the overheating causes the computer portion of the pump to also overheat and thus, creates a communication failure between the ECM and the Injection pump.

Watch for the signs of a bad VP 44 pump:

What is wrong with my VP44 fuel pump? Trouble code P0216

The most common mechanical failure of the VP44 pump is rupturing of the diaphragm in the front of the injection pump. The diaphragm ruptures allowing the timing piston to vibrate and damage the front cover until fuel bypasses. This will cause the dreaded check engine trouble code P0216. When this occurs your Bosch VP44 Injection Pump must be replaced. The rupturing of the diaphragm is caused by a poorly designed lift pump. When the lift pump does not supply the Injection pump with the correct amount of Fuel Pressure (a minimum of 5psi under load at wide open throttle) the diaphragm then doesn’t have enough positive pressure and ruptures. Dodge has recognized this problem as they will no longer even sell the lift pump that goes on the side of the block; they replace it with a unit that is now mounted in the tank.

What is wrong with my VP44, truck will not start or has white smoke? Dead Pedal

A seized rotor is a common problem with 98-99 trucks or ones with a rebuilt pump without an upgraded rotor, coating, and distributor. This mechanical failure of the VP44 is located in the head of the pump and is a communal problem that has plagued the Cummins engines for a long time. According to Bosch this failure is a poorly “de-burred” rotor. This is a problem in the machining, but has been phased out in later years of production. A seized rotor can be contributed to the lift pump not providing enough fuel to the injection pump. Diesel Fuel is used as a lubricant, so when there is an insufficient amount of fuel the rotor does not get lubricated properly. If you are hitting high RPMs down the road and this is happening, you are not getting the lubrication your pump needs and you are likewise going to run into problems. If the rotor seizes the truck will not start and the VP44 Injection Pump must be replaced.

The last reason for the failure of the VP44 pump is electrical problems with the computer on top of the pump. Heat is the main reason associated with this problem, causing the soldered components to become crystallized over time and make bad connections. Lack of fuel is again part of the problem, because the VP44 is cooled with fuel instead of oil (as the old P7100 12valve pumps). When this problem occurs you will usually experience intermittent hard starts, white smoke and what’s usually referred to as “The Dead Pedal”.

What is the cause of a hard start?

Hard starts, as they relate to VP44 injection pump problems, are caused by lack of fuel or over pressurization by the lift pump.  If a lift pump is going bad and failing to supply the proper amount of fuel to the injection pump, then the truck will hard start due to lack of fuel. However, if a new lift pump has been installed and is pushing over 15 PSI to the VP44 injection you can also get hard starts. The VP 44 is a very sensitive pump and needs approx. 12 PSI to run properly. Once you start getting about 15 PSI to the injection you actually begin to over pressurize the pump and cause it to act as if you had flooded the engine.

The above question “What is wrong with my VP44, truck will not start or has white smoke? Dead Pedal” may help in solving hard starts as well.

What will void my warranty on my VP44 pump?

The VP44 pumps will not be warrantied if a user taps or splices the pump wire and does not use a stealth cover. Water damage will also void the warranty, and any repairs that need to be made to the injection pump will be the buyer’s responsibility.