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Home > FAQ > VP44 Injection Pump
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Thoroughbred FAQ's
VP44 Injection Pump

frequently asked questions
Part 1 of VP44 Install Part 2 of VP44 Install
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What is a VP44?

A VP44 electronic rotary distribution pump that distributes and meters high pressure fuel required for injection. It is found on the 1998.5-2002 dodge Ram 2500 and 3500 light duty trucks. The VP44 pump can also be found on several mid-range and agricultural engines.

What will void my warranty on my VP44 injection pump?

The VP44 pumps will not be warranted if a user taps or splices the pump wire If the wires are cut in any way, the pump is no longer under warranty, and any repairs that need to be made to the injection pump will be the buyers responsibility. VP44 warranty can be voided for fuel contamintaion or improper installation. OUr VP44 warranty can also be voided if customer choose to use a fueling box that requires the VP44 pump wire to be tapped. Improper tapping of the wire, electrical malfunction of the box, or mechanical failures that are caused be overspeeding of the VP44 due to performance boxes will not be warrantied.

How much Fuel Pressure Should the VP44 Receive?

There is a diaphragm inside the VP44 that is somewhat sensitive. This particular diaphragm works best under pressures between 10 and 15 PSI. Some pumps will be able to run higher than that but we don't recommend it. After changing your VP44, if you notice continued hard starting or feel as though the pump is getting bogged down, it is probably time to check the lift pump pressure. Our recommendation for optimum fuel pressure is 12 PSI of the VP44.

Does Thoroughbred Diesel's VP44s have new computers (PSG)?

Before a VP44 is rebuilt the computer portion is removed and tested. If the computer does not meet every single one of the qualifications mandated by Bosch then the entire computer is replaced regardless of the failed qualification. If the computer meets all of the Bosch qualifications then it is reused.

What caused my VP44 to Fail? Is this a Common Problem?

The most common cause of VP44 failure is 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.

Does Thoroughbred Diesel Charge for Cores Up Front?

Sometimes. On replacement parts that our customers order frequently we have taken steps to prevent core charges up front. However, on some items we do still require an up front core charge. Check out our core policy page.


Are Thoroughbred Diesel's VP44 Injection Pumps New or Rebuilt?

Bosch is no longer casting housing's for the VP44 injection pump. Therefore, at this time ALL VP44 injection pumps require a used housing, also known as core, to be rebuilt. Due to the need of a core, there is no such thing as a completely new VP44, even though some are advertised as such.

Do the Injection Pumps Come With a Removal Tool?

Our injection pumps do not come with a removal tool. Thoroughbred recommends going to your local parts store and purchasing a steering wheel removal tool. The threaded holes on the gear are M8 x 1.25. You will also need a couple of bolts meeting those specification to attach the steering wheel puller.

Will a Hot Rod VP44 Work On a Stock Truck?

We don't recommend it, however it is possible. Using a Hot Rod VP44 on a stock truck will cause the truck to have a very rough idle, due to the extra pressure the pump is producing. The extra pressure is can also cause issue on stock injectors, which is why Thoroughbred only recommends using a Hot Rod VP44 if you have upgraded injectors designed for a higher flow rate.

Should I Buy the Hot Rod VP44?

If you are planning to upgrade your injectors, then yes, you should upgrade to a Hot Rod VP44. However, for the majority of our customers, you should not upgrade. Yes, it is very tempting to upgrade your injection pump and get the extra HP, but there are more effective ways to gain extra horsepower on a stock truck. We would recommend going with a mild tuner such as the Edge EZ which will give you the extra horsepower and should help to increase fuel economy without any of the side effects associated with the Hot Rod VP44.

How Do I Check Lift Pump Pressure to the VP44?

This method will vary depending on what year your truck is. If you have a 98.5-99 Cummins there will be a 1/8 by 27 NPT port on top of the fuel filter housing. For this year truck, this is the most accurate place to insert your fuel pressure sensor to read the pressure supplied by your lift pump. For trucks ranging in year 99.5-2002 fuel pressure should be checked at the Schrader valve located on the side of the VP44.

How Do I Tell If I Have a 17x or 15x VP44?

Every Bosch pump has a data tag on one side of the pump, drivers side when locate on the vehicle. On this tag there will be a 10 digit Bosch number that is stamped into the metal. The first 8 digits of this number should read 04705060. The last two digits of this number are the identifiers on the type of pump. If the pump is on a light duty Dodge Cummins pickup , and the last two digits are a multiple of 7 then the pump is a 17x. If the last two digits are not a multiple of 7 then it will be a 15x pump. The only exception to this will be if the engine is in an application other than a light duty Dodge Cummins pickup. In which case, the pump could be a 16x or agricultural model.

What is Thoroughbred's Warranty on a VP44?

Thoroughbred Warranty on a VP44 is 1 or 2 year unlimited miles warranty. The two most common things that will void your warranty are fuel contamination and inadequate fuel pressure. Both of these issues can be prevented by upgrading the lift pump system to either an AirDog of FASS fuel system.

What is the Cause Of Hard Starts?

Hard starts as they relate to VP44 injections pumps 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, a newly installed lift pump that is pushing over 15 PSI to the VP44 can also cause hard starts. The VP44 is a very sensitive pump and needs approx. 12 PSI to run properly. Once you start getting about 15 PSI to the injection pump, you actually start to over pressurize the pump causing it to act as if you had a flooded engine.

What Wire Do I Tap on a VP44?

If our customers choose to tap the VP44 for a fueling box, please be aware that this can void the warranty of our pump. If you choose to tap the wire, the correct wire that will need to be connected to is the wire closest to the block that runs to the PSG. A product called the BD Stealh Cover is what we suggest to use to make the installation of the performance module easier, avoiding tapping the wrong wire or tapping incorrectly.

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Thoroughbred Diesel Performance and Repair Shop
4843 Rockwell rd.
Winchester, KY 40391
Call Toll Free: 1-866-737-4966
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