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April 07, 2021 5 min read

The Best Way to Prime a Detroit Diesel Engine

The classic Detroit Diesel DD15 and DD13 engines are complex systems that require careful maintenance and operation. After doing any kind of service on a DD13 or DD15 engine, you are going to have to prime the fuel system before starting.

To successfully prime the engine and avoid damage to the system, it’s very important that you only use DD approved priming devices. Any air trapped in the fuel system can hinder ignition, destabilize fuel pressure, or damage the fuel pump.  

So what is the best Detroit Diesel approved fuel priming device?

To effectively prime a Detroit Diesel DD13 or DD15 engine, use the ESOC 455 fuel primer. This pneumatic fuel primer meets Detroit Diesel OEM requirements by delivering 95 PSI of fuel pressure for 2 minutes.

With a powered DD approved fuel priming device like the ESOC 455, you can prime a DD13 or DD15 fuel system in minutes, successfully start the engine every time, and eliminate the mess and hassle that comes with using a hand pump.


Why do diesel engines need to be primed?


Diesel engines operate with high pressure fuel injection to achieve ignition. This means that the fuel system has to be closed and pressurized to operate properly.

When the fuel supply is emptied (running the engine dry) or engine maintenance is performed, air can get into the fuel system. Pockets of air in the closed fuel system hinders the ability to pump fuel from the tank into the injection ports - therefore impeding successful ignition.


If you attempt to start a diesel engine when air pockets are present in the fuel system, the starter may crank excessively while the fuel pump attempts to pressurize the system. Excessive cranking can unduly wear out the starter and drain the battery. Additionally, diesel fuel is used to lubricate the fuel system including the fuel pump. If the fuel pump is not properly lubricated before cranking the starter, friction can damage the pump’s components and pump failure may occur.


Priming involves delivering high-pressure fuel directly into the fuel system. This ensures that the entire system is pressurized, lubricated, and all air pockets are “bled” from the system.


There are several options for achieving the kind of fuel pressure needed to properly prime a diesel engine.


Hand Priming vs. Powered Priming Devices


There are typically three priming options for diesel engines:


  1. Using the on-engine finger priming pump
  2. Using a hand priming pump
  3. Using a powered priming device


The finger priming pump is found on the side of the fuel filter housing on a DD15 or DD13 engine. This small pump is only for emergency purposes when priming is needed and a priming device is unavailable.


Hand priming pumps can be a good option for your casual priming jobs. If you operate a single truck and just need something to prime the engine after a filter change, a hand priming pump can get the job done on many diesel engines.

If you’re running a fleet maintenance or repair shop that performs multiple maintenances on diesel engines, a hand priming pump is not recommended. Achieving reliable pressure levels throughout the engine prime is difficult with a hand pump. Additionally, using human power to pressurize the canister for every prime is neither practical or economical.


No matter the priming method, always use a Detroit Diesel approved priming device for priming DD13 and DD15 engines.


Powered priming devices are the best option for priming diesel engines because of their reliability, speed, and cleanliness. Pneumatic or electric power is used to achieve a specific fuel pressure and maintain it throughout the entire priming process.


The Best Detroit Diesel Fuel Priming Device


For the busy maintenance facility, fuel priming devices like the ESOC 455 are worth more than their weight in gold because of the time and frustration they save.


The 455 uses pneumatic pressure to take fuel from the truck tank, hold it in the device holding tank, and then send the fuel into the fuel system at the precise pressure needed. The 455 is Detroit Diesel certified which gives you confidence that this priming device meets all OEM requirements for priming DD13 and DD15 engines.


The bonus is a built in fuel filter that makes sure the priming fuel is as clean as possible and ensures successful primes on the first crank.


  ESOC 455 Hand Priming Tool
Powered Fully Pneumatic No
Built-in Fuel Filter Yes No
Priming Pressure 95 PSI Adjustable Variable


Detroit Diesel DD15 and DD13 Priming Procedure


The priming procedure for DD15 and DD13 engines is straight-forward when you use a fuel priming device like the ESOC 455.


The priming procedure is as follows:

Step 1: Fill up the ESOC 455 fuel holding tank

  • Insert draw tube into fuel tank
  • Connect the suction tube hose to the draw tube
  • Connect air supply to the machine using quick-connect fitting
  • Turn on drain switch
  • Open the flow control valve
  • Monitor the orange ball float as it approaches the “max-fill” level
  • Close the flow control valve to stop filling the holding tank
  • Turn the drain switch off

 Step 2: Prime the Engine

  • Disconnect the suction fill hose from the draw tube
  • Connect the compucheck adaptor to the suction fill hose
  • Attach the compucheck adaptor to the priming port on the fuel module of the engine
  • Turn Switch to the present 95 PSI Prime ON
  • Open the flow control valve slowly so as not to shock the fuel system
  • Monitor the orange ball float in the sight guage as it approaches the “Start DD Series Engine” level
  • Start the Engine
  • Idle the engine for about 1 minute
  • Monitor the orange ball float as it approaches the “Turn Off Primer” level
  • Close the flow control valve and then turn the 95 PSI Prime Switch OFF
  • Idle engine at around 1500 RPM for another minute
  • Disconnect the compucheck adaptor from the priming port on the engine


VIDEO: See how the ESOC 455 Works



There you have it, the best way to prime a DD13 or a DD15 engine. Your best bet is to use a Detroit Diesel approved fuel priming device like the ESOC 455 so you don’t risk damaging your fuel system in the priming process. 

Hand pumps work for emergency or one-off primes, but they are not a great long-term priming solution.

The finger pump on the engine is so small that it should only be used in absolute emergency situations. 

Follow the procedure laid out in this article and fuel priming DD15 or DD13 engines should be a breeze.


Fireball Equipment Ltd. is a fuel and lubrication system solution provider – offering top-to-bottom consultation, system design, installation, and continued service.



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