HEUI Fuel Transfer Pump

 Ask Dave / Posted 4 months ago / 78 views


What Fuel Transfer Pump is needed to maintain constant fuel flow and pressure on Cat HEUI (Hydraulic/Electronic Unit Injector) engines 3126A through C-9.


Dave’s Answer:

The fuel pressures for HEUI type injection systems. (Cat 3126 – C-9 engines).

Pressure at low idle: 58 to 63 psi.

Pressure at high idle: 72psi for Cat 3126A-3126E.  80 psi for Cat C-7 to  Cat C-9,

Note that there is a single stage piston type pump for all of above engines making them very prone to low power because the single stage fuel transfer pump cannot maintain a constant fuel flow to injectors. Several members that had injector failures with low power in HEUI type engines.


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 increase 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:

CAT Fuel Priming Pump Parts List r1

Contact details

Fuel System

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