Cold Start up

Tiny
PJMCCARL
  • MEMBER
  • 1996 CHEVROLET EXPRESS
  • V8
  • 2WD
  • AUTOMATIC
  • 110,000 MILES
Having cold start issues that has increased overtime, suspected low fuel pressure, start up pressure seems to be around 55lbs, will hold pressure, seems to be normal leak down once it's started. Tune up has been done, and no codes have been set off. I have read conflicting thoughts on correct start up fuel pressure. Like to get your opinion on.

1. Correct start up fuel pressure?
2. Any thoughts on possible problems?
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Friday, August 20th, 2010 AT 12:37 PM

6 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,758 POSTS
Starting issues in a 1996 Chevrolet Express could indeed be related to fuel pressure problems, and it's good that you've already done some diagnostics. Let's address your questions:

Correct Start-Up Fuel Pressure: Fuel pressure requirements can vary based on the specific engine and its characteristics. However, a common rule of thumb for many vehicles is to have around 40-60 psi (pounds per square inch) of fuel pressure during a cold start. Your reading of around 55 psi seems to be within this range.

Possible Problems: Since you've already performed a tune-up and no codes have been set, it's great that you're considering fuel-related issues. Given the symptoms, here are some potential problems to consider:

Fuel Pressure Regulator: The fuel pressure regulator is responsible for maintaining the proper fuel pressure in the system. If it's failing, it can lead to issues like low fuel pressure during cold starts.

Fuel Pump: While your fuel pressure seems to be within range, it's still worth considering the fuel pump's health. If the pump is struggling to deliver sufficient fuel pressure, it could cause cold start issues.

Fuel Filter: A clogged fuel filter can restrict fuel flow, especially during cold starts when the engine demands more fuel. This could result in starting problems.

Injector Issues: Clogged or malfunctioning fuel injectors can affect fuel delivery, leading to starting issues. You might consider running a fuel injector cleaner or having the injectors professionally cleaned.

Temperature Sensors: Some temperature sensors in the engine control system (like the coolant temperature sensor or intake air temperature sensor) provide data to the engine control module for proper cold start enrichment. If these sensors are providing incorrect readings, it could lead to starting problems.

Vacuum Leaks: Unmetered air entering the engine due to vacuum leaks can cause starting problems. Inspect the intake manifold and vacuum lines for leaks.

Idle Air Control Valve (IAC): The IAC valve controls the engine's idle speed. If it's malfunctioning, it could affect cold starts and idle quality.
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Friday, August 20th, 2010 AT 12:53 PM
Tiny
PJMCCARL
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I want to install a new fuel pump?
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Friday, August 20th, 2010 AT 2:20 PM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,758 POSTS
Please use this guide

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

FUEL PRESSURE SPECIFICATIONS
Ignition On, Engine Off
Central FI 415 - 455 kPa (60 - 66 psi)
SFI 385 - 430 kPa (56 - 62 psi)

I would say your on the right track with fuel pressure. These things won't even run under 55PSI
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Friday, August 20th, 2010 AT 2:30 PM
Tiny
PJMCCARL
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  • 4 POSTS
I have a fuel gauge hook up all the time and have left overnight and start up pressure is 35, once started after 4 or 5 times of starter turnover and starts, it stays at 45. Is there a minimum pressure for this motor?
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Friday, August 20th, 2010 AT 2:55 PM
Tiny
WRENCHTECH
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Yes, the low end of the spec is the minimum. I know these systems have no tolerance for low pressure. Like I said, many of them won't even run under 55PSI.
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Friday, August 20th, 2010 AT 3:09 PM
Tiny
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Thanks guys, I'll replace the fuel pump and get back to o if that doesn't work.
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Friday, August 20th, 2010 AT 4:20 PM

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