Code P0171, crank no start?

  • 5.7L
  • V8
  • 2WD
  • 180,000 MILES
Hi Guys,

My van (Express 3500) has P0171 code; it cranks good but won't start. The fuel pressure readings are 62psi and then drops quickly to 55, then to 30 in about 15 minutes.

I suspected the fuel pressure regulator or fuel pump. So, I replaced the fuel injector/spider assembly with a rebuilt one, also a new FPR. No change in the readings.

I then replaced the fuel pump (aftermarket) and filter. Still no change in the readings and still won't start.

What else could be my issue? Is it possible the fuel pump or FPR is defective?

Also, the front seal is leaking oil pretty badly onto the crankshaft sensor. Is it possible that could be causing the no start condition?

Thank you for your help and assistance.

I'm going to try to figure a way to deadhead the fuel pump to test it.
Wednesday, August 23rd, 2023 AT 5:59 PM

1 Reply

  • 42,840 POSTS
Does the engine run on starting fluid? If so, it sounds like you got a defective fuel pump. Can you turn the key on and see how fast the pump can get to 60 PSI, if slowly the pump is defective, here is information on the code which included a bad fuel pump. Please check out this guide as well:

The P0171 code is a common trouble code that appears in vehicles across various manufacturers, including Chevrolet. It indicates that the engine control module (ECM) has detected a lean condition in the engine's air-fuel mixture on Bank 1. In simpler terms, the engine is receiving more air than it should in relation to the amount of fuel being injected, causing the mixture to lean out.

Here are some potential causes and steps to address the P0171 code in your 2001 Chevrolet Express:

Vacuum Leaks: Vacuum leaks in the intake manifold or vacuum hoses can allow excess air to enter the engine, leading to a lean mixture. Check for cracked hoses, loose connections, or intake manifold gasket leaks.

Faulty Mass Air Flow (MAF) Sensor: The MAF sensor measures the amount of air entering the engine and helps the ECM determine the appropriate fuel injection. A malfunctioning MAF sensor can provide inaccurate readings, affecting the air-fuel mixture.

Faulty Oxygen Sensors: Oxygen sensors (also known as O2 sensors) monitor the oxygen levels in the exhaust gases and provide feedback to the ECM for adjusting the fuel mixture. A faulty O2 sensor, especially the upstream (pre-catalytic converter) one, can cause a lean condition.

Fuel Delivery Issues: A clogged fuel filter, weak fuel pump, or restricted fuel injectors can lead to insufficient fuel delivery, causing a lean mixture.

Exhaust Leaks: Leaks in the exhaust system can allow extra air to enter the exhaust stream, affecting oxygen sensor readings and leading to a lean condition.

Dirty or Clogged Fuel Injectors: Dirty or clogged fuel injectors may not deliver the proper amount of fuel, causing a lean mixture.

Engine Vacuum Issues: Some issues with the engine's vacuum system can cause a lean condition. These might include problems with the PCV system or EGR valve.

Intake Air Leaks: Leaks in the air intake system after the MAF sensor can disrupt the air-fuel mixture calculation.

Please go over these guides and get back to us.
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Thursday, August 24th, 2023 AT 12:56 PM

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