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Tim's Auto Repair
Tim's Auto Repair, mechanic
Category: Chevy
Satisfied Customers: 16036
Experience:  Have owned a repair shop for 25 yrs.
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1998 chevy: liter..changed fuel pump..fuel pressure, nothing comming

Customer Question

Have 1998 chevy cheyene 5.0 liter changed fuel pump pressure rguator and filter.truck wants to start, started once ran for couple minutes and shutoff.Plenty of fuel pressure, nothing comming back from return line
Can run if spray either in it
Submitted: 6 years ago.
Category: Chevy
Expert:  Tim's Auto Repair replied 6 years ago.


when you say it has plenty of fuel much does it have in psi?

please tell me all you can


Customer: replied 6 years ago.

went to store was low on fuel, came out of store truck started and shut off, could not hear fuel pump like usual. Changed fuel pump regulator and filter.Pulled fuel line off intake good pressure.Also pulled plugs checked spark good spark.

Truck will idle ruff if fuel is poured into intake

pulled plugs look wet


it seems to get good spark, and plugs are wet so seems to get fuel.could it be to much i don't know

truck wants to start but won.t

Expert:  Tim's Auto Repair replied 6 years ago.


how much fuel pressure is plenty?how much psi?

Customer: replied 6 years ago.
60psi to the engine
Expert:  Tim's Auto Repair replied 6 years ago.


does it have 60psi while turning the starter?

did the engine light stay on when it was running?if so,can you give me the computer codes?

Customer: replied 6 years ago.

engine light does not come on have no codes

almost seems like it flooded

no 60 psi while starting

Expert:  Tim's Auto Repair replied 6 years ago.


and i will start if you put fuel in the throttle body? removed the intake and replaced the regulator?and you have no fuel coming out of the fuel metering body return line?please explain

Customer: replied 6 years ago.
no there is no fuel comming out of the return line what so ever
Expert:  Tim's Auto Repair replied 6 years ago.


these fuel pumps have about 90psi and regulate at 60psi...fuel must come out of the metering body..if not,,your pump is you have a fuel pressure tester with you now?

Customer: replied 6 years ago.

it's a new pump

i do not have a pressure tester


when push down you get about 6 inches of spray

when you try to start you get about 4 inches

Expert:  Tim's Auto Repair replied 6 years ago.

how do you know how much spray you are getting/?is this not a vortec?this is a 1998 model right?

Customer: replied 6 years ago.
it's a vortec 5000 (5.0L) 305 no pressure indicator got sprayed in the face when took supply line off but took return line off no gas
Expert:  Tim's Auto Repair replied 6 years ago.


you need to recheck the fuel pressure with a known good test gage....these vortec engines must have no less than 60psi of regulated pressure,,sense there is no fuel coming out of the return and it will start when primed..i think the new fuel pump is weak..recheck the pressure




Testing and Inspection



Circuit Description
When you turn ON the ignition switch, the Vehicle Control Module (VCM) turns ON the in-tank fuel pump. The pump remains ON as long as the engine is cranking or running and the VCM is receiving reference pulses. If there are no reference pulses, the VCM shuts the fuel pump OFF within 2 seconds after you turn the ON the ignition or if the engine stops.

An electric fuel pump pumps the fuel through an in-line filter to the Central SFI unit. The pump is attached to the fuel level meter assembly inside of the fuel tank. The pump is designed in order to provide fuel at a pressure above the regulated pressure needed by the injectors. The pressure regulator keeps the fuel available to the injector at a regulated pressure. Unused fuel is returned to the fuel tank by a separate line.

Diagnostic Aids
Tools Required


  • J 34730-E Fuel Pressure Gauge.
  • J 34730-1A Fuel Pressure Gauge with J 34730-250 Fuel Pressure Adapter Kit.
  • d 42873-1 3/8 Fuel Feed Pipe Shutoff Valve and the J 42873-2 5/16 Fuel Return Pipe Shutoff Valve.

Test Description

Diagnostic Chart
Diagnostic Chart
Diagnostic Chart
Diagnostic Chart
Diagnostic Chart
Diagnostic Chart

The numbers below refer to the step numbers on the diagnostic table.


  1. Wrap a shop towel around the fuel pressure connection to absorb any small amount of fuel leakage that may occur when installing the fuel pressure gauge. Turn ON the ignition leaving the engine OFF, the fuel pressure should be 415 - 455 kPa (60 - 66 psi) . This pressure is controlled by a spring pressure within the regulator assembly.
  1. The fuel pressure that continues to fall is caused by one of the following items:
    • The in-tank modular fuel sender is not holding pressure.
    • The fuel pressure regulator valve is leaking.
    • A Central SFI injector is leaking.
    • Fuel line is leaking.
  1. When the engine is idling, the manifold pressure is low (high vacuum) and is applied to the fuel pressure regulator diaphragm. This will offset the spring and result in a lower fuel pressure. This idle pressure will vary somewhat depending on the barometric pressure; however, the pressure at idle should be less indicating the pressure regulator control.
  1. If the fuel pressure is less than 415 kPa (60 psi), it falls into the following 3 areas:
    • The pressure is regulated but less than 415 kPa (60 psi).The amount of fuel reaching the injector is sufficient, but the pressure is too low. The system will run lean, hard starting cold, no start, overall poor performance, and may set a DTC. A restricted flow causing pressure drop-Normally, a vehicle with a fuel pressure of less than 300 kPa (44 psi) at idle is inoperable. However, it the pressure drop occurs only while driving, the engine will normally surge then stop running as the pressure begins to drop rapidly. This is most likely caused by a restricted fuel line or plugged filter.
    • A leaking or contaminated pressure regulator valve or seat interface may not allow the regulated pressure to be achieved.

Notice: Do not allow the fuel pressure to exceed 517 kPa (75 psi) . Excessive pressure may damage the fuel pressure regulator.

  1. Restricting the fuel return line allows the fuel pressure to build above regulated pressure. With the battery voltage applied to the fuel pump test terminal, the pressure should rise above 455 kPa (66 psi) , as the valve in the return line is partially closed.


Engine Cranks, But Will Not Run


Diagnostic Chart
Enhanced Ignition System

Circuit Description

This table assumes that the battery condition and the engine cranking speed are OK, as well as having adequate fuel in the tank.

Diagnostic Aids

If no trouble is found in the fuel pump circuit or the ignition system and the cause of an Engine Cranks But Will Not Run has not been found, check for the following conditions:


  • Fouled spark plugs
  • An EGR valve stuck open
  • Low fuel pressure. Refer to Fuel System Diagnosis (System Check). See: Component Tests and General Diagnostics\System Check
  • Water or foreign material in the fuel system
  • A grounded Ignition Control (IC) signal circuit may cause a No Stan or a Start then Stall condition
  • Basic engine problem

The Vehicle Control Module (VCM) has integrated IC circuits that are fault protected; therefore, if a circuit has failed, the integrated IC may not be damaged. If that is the case, the IC will keep the circuit open until the fault in the circuit has been corrected.

When the fault has been corrected, reinstall the VCM and check the circuit. Replace the VCM only if the circuit is still inoperative.

Test Description

The numbers below refer to the step numbers on the diagnostic tables.

  1. If the signal is over 2.5 volts, the engine may be in the clear flood mode which will cause starting problems.
  2. If the engine coolant sensor is below -30°C, the VCM provides fuel for this extremely cold temperature which will severely flood the engine.
  1. Use the injector test lamp J 34730-350 in order to test the injector circuit. A blinking lamp indicates that the VCM is controlling the injector.
  2. Voltage at the spark plug is checked using the spark plug tester tool J 26792. No spark indicates a basic ignition problem.
  3. This test will determines if there is fuel pressure at the fuel injection unit and holding steady.