VP44 Injection Pump – What you need to know

vp44 injection pump

How much Fuel Pressure Should the VP44 Injection Pump Regularly Receive?

There is a diaphragm located inside the VP44 injection pump that is very sensitive.  This VP44 diaphragm works best under pressures between 10 and 15 PSI. Some pumps will be able to run higher than that but Thoroughbred Diesel does not 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 VP 44.

How Do I Check Lift Pump Pressure to the VP44?

This method will vary depending on what truck year you have. 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 located on the side of the VP44.

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 steering wheel removal tool. The threaded holes on the gear are M8 x 1.25. You we also need a couple of bolts meeting those specs.

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.

Will a Hot Rod VP44 injection pump 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 design for a higher flow rate.

Should I Buy the Hot Rod VP44?hot rod vp44 injection pump

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 50 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 Tell If I Have a 17x or 15x VP44

Every Bosch manufactured pump has data tag on one side of the pump, driver’s side when located on vehicle. On this tag there will 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 of 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.

What Wire Do I Tap on a VP44 Injection Pump?

There are two wires running from the back of the pump up to the computer portion on the top of the pump. This computer portion is known as the PSG. The wire that is closest to the engine and connects to the PSG is the wire that needs to be taped for installation of some modules.

Click here to see how to tap a VP44 Injection Pump in our video using a BD Diesel Stealth Cover! >>

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 upfront core charge. Check out our core policy page.


What is Thoroughbred’s Warranty on a VP44 injection pump?

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

Where can I buy a VP44 pump?

Thoroughbred Diesel offers replacement Bosch Vp44 Fuel Injection Pumps that have been rebuilt by a certified Bosch tech and have been tested on a test stand for 4hrs before the pump is sent to a customer. Bosch VP 44 diesel pumps are also upgraded with all the latest upgrades required by Bosch. The VP44 injection pumps come with a 1yr unlimited mileage warranty. If you unsure or just want some free advice on your pump you can reach them at (866) 737-4966.

Whether you are looking for a stock vp44 injection pump or a high performance one for those days at the track, Thoroughbred Diesel has the pump for you. We also offer VP44 packages that nobody else offers.

shop now at Thoroughbred Diesel

Read about common problems and solutions to VP44 Pumps! >>

buy vp44 cores



  • Dan Riley says:

    I’ve had friends say I need a new injection pump. I am not sure. 2000 dodge, stock 5.9. It has a FASS lift pump. When I first start it, it runs excellent. As it warms up it develops a skip, or miss. Just one strong skip, then it runs excellent again for several minutes and then another skip. The skips happen closer together until it runs rough and if let to idle will stall. It starts right up after stalling.

    I have driven it up to 30 minutes without missing a beat then skip, etc.

    Do I need an injection pump? I am an ASE master tech on gas engines but I know little about these diesels.

    Thank you for any help you can give.

    Dan Riley

  • Andrew says:

    How do you set timing on a vp44. And how can you tell what the timing is already set to?

  • tbreddiesel says:

    The VP’s are key timed to the engine, and the pump is internally timed to the key size. Long story short, as long as you have the VP’s key properly aligned in the pumy gear, then you have the pump timed properly to the engine.

  • tbreddiesel says:

    The first thing you will need to do is observe your lift pump pressure while the truck is running. Does it maintain proper fuel pressure?

  • Andrew klahold says:

    I have a 99 dodge cummins rebuilt engine with new block old block cracked i had a miss skipping problem and put in new injectors that solved that but i have also had a hot engine starting problem injector pump has 400.000 miles on it. My question is is the malfuctioning. Cause of fuel temperture

  • tbreddiesel says:

    Next time the truck hard starts, take the power away from your lift pump and see if the truck starts. If it does, you have a diaphragm problem in the pump.

  • richard williams says:

    do you have the PSG for the VP44 injector pump

  • tbreddiesel says:

    We do not sell the PSG’s by themselves, only fully assembled and tested pumps.

Leave a Comment