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 with AVCS

Software affected:

xxxx and newer

Firmware affected:

xxxx and newer

Purpose

On startup the ECU commands 100% duty from the fuel pump via the pump controller for a significant period of time i.e. 30 seconds.

For vehicles with stock fuel pumps, this poses no concern, but we wanted to provide an improvement for the following use case:

The vehicle has an upgraded fuel pump, still utilizing the factory return line, OEM FPR (fuel pressure regulator), and pump controller.

When the pump is commanded to 100% duty cycle, it flows enough fuel that the return system cannot support the excess flow, causing an unwanted increase in fuel pressure.

This is commonly referred to as "over-running the regulator".

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 applicable ECUs were further reverse engineered to find the table which determines the duration of time the ECU commands the pump to 100% post-start.

That table has been made accessible in our tuning software, under the Fuel Pump sub-folder in the Fuel Tables section.

Suggested Adjustment

Start engine, let idle while logging fuel pressure differential or watching a fuel pressure gauge and MAP reading to determine current fuel pressure vs. desired fuel pressure. Be sure to also view the Fuel Pump Duty monitor on the AP, or via ATP. See if fuel pressure is on target while fuel pump duty is 100%, and then at 33%.
1. If fuel pressure stays on target or close to it while fuel pump duty is 100% and 33%, this table does not need adjusted.
2. If fuel pressure strays significantly over the appropriate level while fuel pump duty is 100% and 33%, you have a situation that cannot be resolved by adjusting this table. One of the following is likely occurring:
  1. The pump is no longer being controlled via the pump controller due to wiring changes.
  2. The pump flows so much, that even at 33% duty it is outflowing your FPR and/or return hose
  3. You have an adjustable FPR that needs adjusted
3. If fuel pressure strays significantly over the appropriate level while fuel pump duty is 100%, but is on target when fuel pump duty drops to 33%, you will likely benefit from adjustment of this table. I suggest reducing the value to 5 seconds as a starting point, then adjust from there to achieve desired results.
  1. Caution is suggested if considering very low values since flushing the lines quickly on a hot restart does improve engine operation.