Fix P2291: Mechanic’s solutions that WORKED

The OBD2 code P2291, indicating “Injector Control Pressure Too Low – Engine Cranking,” is a common issue in Ford Super Duty trucks, pointing to difficulties in building enough pressure in the high-pressure fuel system during engine startup. This condition can prevent the engine from starting due to insufficient fuel pressure to properly inject fuel into the combustion chamber.

P2291 quick overview

Meaning	P2291: Injector Control Pressure Too Low – Engine Cranking
Is it serious?	Yes, as it can prevent the engine from starting, rendering the vehicle inoperable.
Possible causes	– Faulty high-pressure fuel pump (HPFP) – Injector issues, including leaks or blockages – Contaminated fuel system with debris or metal shavings – Faulty fuel pressure regulator or sensors
How to diagnose?	Inspect the high-pressure fuel pump for signs of wear or damage. Check the injectors for proper operation and signs of leakage. Evaluate the fuel system for contamination and clean or replace components as necessary. Test fuel pressure sensors and regulators to ensure accurate pressure readings. Flush the fuel system to remove any debris or contamination.

How to fix P2291 – learn from mechanics

I looked into P2291 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Ford

Vehicle information 2010 Ford F-350 Super Duty King Ranch 6.4L

Issue + repair history

• No start issue
• Codes P2291 and P2291FF
• Replaced FRP Sensor
• Low fuel pressure (3lbs cranking)
• Debris found in high-pressure pump
• Planning to replace injectors due to debris

Other OBD2 Codes + Test Results

• P2291: Low fuel pressure
• Test results: low psi pump test – 3 psi cranking

Mechanic suggestions

• Check for oil overfilling, ensure low-pressure fuel system is functioning properly.
• Investigate possible issues with high-pressure system, including the fuel volume control valve (FVCV) and fuel pressure control valve (FPCV).
• Check for stuck injector ball seat, which could cause low rail pressure.
• Consider replacing high-pressure pump or injectors, as they are commonly associated with this issue.
• Flush the fuel system to remove metal debris and consider replacing high-pressure fuel rails.
• Replace low-pressure fuel pump as a precautionary measure.

Final fix

• Replaced high-pressure pump and planning to replace injectors due to metal debris found.

Case #2: Ford

Vehicle information 2008 Ford F-450 Super Duty XL 6.4L

Issue + repair history

• No start issue
• MIL lamp on with code P2291 (ICP low cranking)
• Replaced high-pressure fuel pump (HPP)
• Fuel pressure fluctuates from 200 psi to 2200 psi after multiple high-pressure system bleeds
• Fuel tank delamination causing contamination in the fuel system
• Clean fuel with no water/metal contamination
• No abnormal noise during cranking
• Relative compression is good in all cylinders

Other OBD2 Codes + Test Results

• P2291: ICP low cranking
• Test results:
  • Low Pressure Fuel Check: 5 psi
  • FRP cranking: 200-2200 psi
  • FRP voltage: 0.51-0.61
  • F_PCV: 33-50 percent
  • F_VCV: 33-50 percent
  • Relative Compression: Pass 100 percent all cylinders

Mechanic suggestions

• Consider the possibility of metal shavings from the high-pressure pump contaminating the fuel system, necessitating injector replacement.
• Check warranty coverage for potential repair costs.
• Flush all fuel lines and components thoroughly to remove any debris.
• Ensure proper oil change after high-pressure fuel pump replacement.

Final fix

• Discovered fuel tank delamination causing contamination in the fuel system, necessitating a rebuild of the fuel tank.

Case #3: Ford

Vehicle information 2011 Ford F-250 Super Duty King Ranch 6.7L

Issue + repair history

• No start concern with a P2291 low high-pressure code in PCM
• Replaced HFP sensor and HPFP, still no start
• Disconnected fuel return line, observed fuel flow changes with KOEO and cranking, confirming PCV operation
• No metal shavings found in fuel system during HPFP replacement
• HPF sensor reads between 65-300 psi while cranking
• Tuner reset PCM to factory settings, but no change
• Final fix: #4 injector found to be faulty, causing the no-start condition

Other OBD2 Codes + Test Results

• P2291: Injector Control Pressure Too Low – Engine Cranking
• Test results:
  • Low side pressure: 60 psi
  • Fuel filters: Good
  • PCV: Good
  • VCV: Unknown

Mechanic suggestions

• Check wiring at both valve and pressure sensor for high resistance
• If metal shavings are found in the HPFP, consider replacing multiple components including injectors, lines, filters, and sensors
• Verify the functionality of the crank positioning sensor
• Check injector return flow, which can affect rail pressure on common rail systems
• Measure injector return flow to assess potential excessive leakage, a common issue on common rail fuel systems

Final fix

• Identified #4 injector as faulty, causing the fuel system to fail to achieve high fuel pressure and resulting in a no-start condition.

Diagnostic Step	Explanation
Inspect high-pressure fuel pump	Check for wear, damage, or signs of contamination that could impair function.
Check the injectors	Evaluate for leaks, blockages, or failure that could affect pressure.
Evaluate the fuel system for contamination	Look for debris or metal shavings that could hinder fuel flow.
Test fuel pressure sensors and regulators	Ensure they provide accurate readings and control fuel pressure correctly.
Flush the fuel system	Remove any contaminants to restore clean fuel flow to the engine.

In these service cases, solutions ranged from replacing high-pressure fuel pumps and injectors to addressing contamination issues within the fuel system, illustrating the need for a thorough diagnostic process to identify and correct the underlying cause of P2291 effectively.