Fuel Transfer Pump for HEUI Equipped Engines (3126 - C9)


 Ask Dave / Posted 2 years ago / 4529 views

Question: Why Do HEUI equipped engines sometimes start hard or seem to lose power?

Dave’s Answer:The HEUI injection system has a single stage piston fuel transfer pump that runs off the HEUI pump. As the engine and fuel system ages, the fuel transfer pump can begin having problems maintaining a constant flow and pressure. Causes for this include air in the fuel system from deteriorating fittings and faulty fuel line connections, aftermarket fuel /water filter systems that are not maintained, rubber particles from hydraulic hoses used for fuel lines, fuel tank pick-up tube at top of tank, fuel tank vent plugged, and the fuel pressure regulator failing and allowing no pressure to be retained in the cylinder head. Contaminants can be prevented from reaching the engine by avoidance of after-market secondary fuel filters and use of a Cat 1R-0751 filter. The lack of constant fuel flow and pressure can cause injector(s) to stick from lack diesel fuel needed to cool the injectors, low power, hard starting after sitting as the fuel bleeds back away from the engine and toward the tank. Even when the sources of air and contamination are resolved, the problem of low pressure can exist as the pump cannot supply enough fuel due to age and/or the length of the fuel line form the tank. Installation of a Cat electric fuel pump will resolve this by providing constant pressure and flow, regardless of the distance to the fuel tank. This system has been installed by a number of BAC members, (Jim Nichols and Mark Bryant). Both report excellent results with faster starting and increased power and engine performance.

In summary, low fuel pressure can cause low power. Air in the fuel system can cause injector failure and loss of power. Contaminants allowed past the secondary fuel filter can require replacement of injectors and cleaning of the complete fuel system.

Picture of pump:

Electric Fuel Pump picture


Parts list for installation of pump:

Note: See “Electric Fuel Pump Installation” for an updated parts list, especially if you are modifying a 3126 series engine

CAT Fuel Priming Pump Parts List r1

We’ve had the following questions regarding pump installation:

1.      It seems to me that the kit includes a toggle switch so as to use the pump only intermittently.  I was under the impression that this pump would run continuously to supply better fuel flow. Am I not understanding this correctly?

2.      I originally thought that a separate Electric Fuel Pump was required in addition to the Priming Pump Kit with the Fuel/Separator 206-5756. What I see now is that ONLY the 206-5756 is required, is this correct? Any long term info on the longevity of the Priming Pump? I would assume that it was not originally designed as a 100% duty cycle pump.

Dave’s Answers:

The Caterpillar Electric Fuel Pump needs to be wired into an on/off key circuit so every time engine starts and runs the electric pump runs, it runs all the time engine runs. Note: this Caterpillar electric fuel pump was made for continuous running on off road equipment, and on road trucks. The constant fuel flow and pressure it provides will meet and exceed requirements for Caterpillar C-9 engine and down to Caterpillar 3126. It will  run 100 % of the time with little or no problems. Note many questions I received from  members indicated that they think the Electric Fuel Pump is a priming fuel pump with an electric motor, the same as the Racor water/fuel filter, it is not.  The Cat Electric Fuel Pump runs constantly to provide constant fuel flow and pressure for HEUI injection systems.


Contact details

Fuel System

Comments are closed.

Powered by WordPress. Designed by WooThemes