Fuel System Trouble shooting

   The following section covers fuel pressure testing with fuel filter removal and replacement, (faulty) fuel regulator removal and installation on a 2001 Chevy Suburban with a 350 CID fuel injected engine at 42k miles.

    Per the repair manual that I used the fuel pressure for the 2001 Chevy with a 350L engine is 60~66 PSI.

   

 

Failure Mode: Rough idle

Special Equipment:  Fire extinguisher,  Fuel pressure gauge 0 - 100 PSI w/ pressure relief, pan

Fuel pressure test configuration and relief for fuel filter replacement :

  1. Verify/Power off the vehicle and remove the keys.

  2. Open the hood and remove the VORTEC engine cover (Remove the bolt and gently  lift up on the front of the cover)

  3. Verify the engine and exhaust manifolds are cool.

  4. Remove the gas cap to relieve fuel tank pressure.

  5. Locate the Schrader valve on the passenger side of the vehicle attached to the fuel rail (see picture below).

  6. Place the ABC fire extinguisher close for quick access.

  7. Remove the Schrader valve Cap. 

  8. Attach the fuel pressure gauge to the Schrader valve and hand/finger tighten down.

  9. Drape the fuel gauge pressure relief hose out of the engine compartment down the fender into the PAN

  10. Relieve the fuel rail pressure via the pressure gauge relief valve.

Removal Steps (Fuel filter)

  1. Verify/Power off the vehicle and remove the keys.

  2. The fuel filter is located underneath drivers side door inside the vehicles frame.

  3. "Warning"  - Use extreme caution while  jacking up and supporting (w/jack stands) the vehicle.

  4. "Warning"  - Be prepared for fuel spillage from the fuel filter and lines.  Use a pan to collect the fuel.

  5. Jack up the left side of the vehicle and support it with the appropriate jack stands in a proper fashion

  6. Locate the fuel filter loosen the mounting hardware holding the filter. Note the fuel filter orientation.

  7. Fuel will spill out.  Loosen the input and output fuel lines and remove the fuel filter.

Installation Steps (Fuel filter)

  1. Install the new fuel filter oriented correctly and tighten the input and output fuel lines.

  2. Tighten the fuel filter mounting hardware.

  3. Lower the vehicle.

  4. Install the fuel tank gas cap.

  5. Prepare to monitor the fuel pressure gauge and fuel filter for leakage.

  6. Have an assistant start the vehicle while the vehicle is running check the fuel filter for leaks.

  7. Monitor the fuel pressure it should between 60 and 66 PSI. 

  8. Have the assistant rev the engine and verify that the fuel pressure remains between 60 and 66 PSI.

  9. Power of the vehicle and remove the keys.

  10. If its stable you are done go to the the Fuel Pressure Test Configuration Breakdown.

 

 

 

Low fuel pressure Trouble shooting

    The fuel pressure measurement that was observed on this particular vehicle was 50 PSI which was 10 PSI lower than the specifications. With a new fuel filter installed the probability of a inlet restriction was low.  This left the following choices: the fuel pump in the fuel tank was bad, the fuel pressure regulator was bad, or the fuel pressure regulator control vacuum was leaking.  I started the vehicle and checked for vacuum leaks which I could not locate (it appeared nominal). Instead of verifying the fuel flow being supplied from the fuel tank was sufficient I gambled that the 20 dollar fuel regulator was bad (it's easy to change on this vehicle. 

 

Left to right, Schrader valve w/cap, fuel pressure regulator, regulator close up.

 

Removal steps

  1. "Warning"  - Be prepared for fuel spillage from the fuel regulator and rail. The engine must be cold.

  2. Remove the gas cap.

  3. Relieve the fuel rail pressure via the pressure gauge relief valve.

  4. Place the ABC fire extinguisher close for quick access.

  5. Remove the vacuum hose from the fuel pressure regulator.

  6. Remove the ring/clamp holding the fuel pressure regulator to the fuel rail (see picture above).

  7.  Use a pan to collect the fuel. Perform removal steps 3 thru 6 in reverse order.

  8. Start vehicle and perform a test drive.

Installation steps

  1. Install the new fuel pressure regulator with the vacuum line facing up.

  2. Install the ring/clamp

  3. Connect the vacuum line to the fuel pressure regulator.

  4. Install the gas cap.

  5. Have an assistant start the vehicle while the vehicle is running check the fuel regulator for leaks.

  6. Monitor the fuel pressure it should between 60 and 66 PSI. 

  7. Have the assistant rev the engine and verify that the fuel pressure remains between 60 and 66 PSI.

  8. If it's not then there's a fuel supply issue and there are two choices the first is a fuel restriction in the line, the second and most likely cause is a bad fuel pump in the fuel tank.  I have not had the privilege to remove and replace a fuel tank pump yet, but it's rather involved.

Fuel pressure test configuration removal

  1. Verify/Power off the vehicle and remove the keys.

  2. Relieve the fuel rail pressure via the pressure gauge relief valve.

  3. Remove the fuel guage from the Schrader valve.

  4. Install the Schrager valve cap.

  5. Install the VORTEC cover

  6. Properly dispose the fuel in the PAN.

  7. Have an assistant start the vehicle while the vehicle is running check the fuel rail, Schrader valve, fuel regulator, and fuel filter for leaks.

Operation Complete.

Old fuel regulator pictures