Tech Bulletin - Fuel Pump Duty Post-Start High Level Activation (Max. Engine Run Time)
Date: 7/13/22
By: Mike McGinnis
Vehicles affected:
- All CCF ECU Types for EJ 2.5 liter engines
- CCF and MAF ECU Types for EJ 2.0 liter engines with AVCS
Software affected:
- xxxx and newer
Firmware affected:
- xxxx and newer
Table of Contents maxLevel 5 minLevel 2
Purpose
The ECU commands 100% duty cycle from the fuel pump via the fuel pump controller for startup, and for a significant period of time post engine start i.e. 30 seconds.
For vehicles with stock fuel pumps, this poses no concern, but we wanted to provide an improvement for some vehicles utilizing upgraded fuel pumps that retain use of the factory fuel pump controller.
When the fuel pump output is commanded to 100% duty cycle, and engine demand for fuel is low, the pump may flow more fuel than the return system can support.
This causes an unwanted increase in fuel pressure commonly referred to as "over-running the regulator", but the return line itself or other parts of the system may be the limiting factor.
The excess fuel pressure causes the engine to run richer than expected, since injector output increases with an increase in differential fuel pressure.
Solution
The solution to over fueling due to excess fuel pressure during this post start period, is reducing fuel pump output to get fuel pressure back on target.
To achieve this, applicable ECUs were further reverse engineered to find the table which determines the duration of time the ECU commands the pump to 100% duty post engine start.
That table has been made accessible in our tuning software, under the Fuel Pump sub-folder, in the Fuel Tables section.