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Tim's Auto Repair
Tim's Auto Repair, Mechanic
Category: Car
Satisfied Customers: 13068
Experience:  Have owned a repair shop for 25 yrs.
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Chev...truck with a 5.0 Liter vortex engine Im having a problem

Resolved Question:

I have a 1996 chev. truck with a 5.0 Liter vortex engine I'm having a problem starting. I can hear the fuel pump whine when it pressures up, like it always does. I can crank it over and over and it tries to start just some time. I crank and crank with it trying to hit. I was wondering is there an automatic choke that's bad.I've had to press the accelerator before each starting attempt for awhile now the only difference it always started.
Submitted: 4 years ago.
Category: Car
Expert:  Tim's Auto Repair replied 4 years ago.
Chat Conversation Started
tims auto repair :

hi

tims auto repair :

this sounds as if you may have a weak fuel pump

tims auto repair :

these must have no less than 60psi at all times..even while turning the starter

Customer :

I had the pump changed about two years ago. If it was the pump wouldn't it miss going down it highway.

tims auto repair :

not always

tims auto repair :

these vortec engines must have allot of pressure to start

tims auto repair :

sometimes,when the pump is bad,the starter will pull the amps away from it,,because the pump needs more amps

Customer :

what about the fuel pressure regulator, I had that changed also

tims auto repair :

well

tims auto repair :

the odds are slim on it being the regulator

tims auto repair :

but

tims auto repair :

dont throw parts at it

tims auto repair :

test the pressure first

Customer :

Is there anyway I can check the pump pressure??

tims auto repair :

the pressure test will tell us allot

tims auto repair :

yes

tims auto repair :

do you have a test gage?

Customer :

no, and I wouldnt know where to connect anyway

tims auto repair :

ok

tims auto repair :

i will send you instuctions

Customer :

If pressure is good, what would be next on your list to check

tims auto repair :

well

tims auto repair :

you will need to check for spark on theplug wires

tims auto repair :

if..no spark..it may need atune up....these vortecs are bad about burning up the rotor or the distributer cap

tims auto repair :

caused from bad plug wires

tims auto repair :

if the fuel pressure is low..replace the fuel filter first

tims auto repair :

but

tims auto repair :

i would think the problem is the pump......common problem

Customer :

Actually, that's what I had done about three years ago new rotor etc .It did burn all that up.

Customer :

I'll try checking pressure if you send me instructions.

tims auto repair :

ok..i will need to leave the live chat

tims auto repair :

stand by

Expert:  Tim's Auto Repair replied 4 years ago.
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Expert:  Tim's Auto Repair replied 4 years ago.

this should help you..please print

thanks

 

 

fuel pressure

Testing and Inspection

 

Diagnostic Chart
Diagnostic Chart
Diagnostic Chart
Diagnostic Chart
Diagnostic Chart
Diagnostic Chart
Description

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

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.

 

Expert:  Tim's Auto Repair replied 4 years ago.

check the pressure while turning the starter when it wont start

thanks

Tim's Auto Repair, Mechanic
Category: Car
Satisfied Customers: 13068
Experience: Have owned a repair shop for 25 yrs.
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