2003 trailblazer, 4.2..... No vacuum to the fuel pressure regulator. Why?

right hand side of the engine looking at vehicle from Hood has a little tiny vacuum line coming from plenum to fuel pressure regulator regulator has hard steel lines connected to it leading to firewall if this doesn't help Google year make model and regulator

fuel injected car do not get vapor lock,check you fuel pressure,if it is OK (with in spec) pull the vacuum line from fuel pressure regulator if it is wet (gas in it) then you need a regulator as the diaphragm is ruptured ,also bad T.P.S (thrittle position sensor) can cause the same sympton

Please verify the year of your truck. A 2003 Chevy Trailblazer has a 4L60E transmission. This transmission does not have a vacuum modulator valve. The 4L60 uses a vacuum modulator valve but the last year for that transmission was 1992. The perpose of the modulating valve is to control/regulate line pressure. The line pressure in a 4L60E is computer controlled or controlled electrically.

check fuel pressure regulator for fuel in vacuum line ,check fuel filter , and alot of those models needed a top engine clean where u drip top engine cleaner through the air tube to clean valves .
we have done this action quite a few times with good results where i work
for some reason these 4.2 ltr engines seam to gum up on valves alot

There is only 4 vacuum lines on that engine

1- brake booster line

2- purge line to purge solenoid (top center of throttle body)

3- PCV hose. run straight from PCV to side of intake at base of throttle body

4- fuel pressure regulator line (short small diameter hose runs from #6 intake runner to fuel pressure regulator

5- tube that connects front cam cover to rear cam cover to improve vapor venting

http://www.hyundai-forums.com/attachments/gk-tiburon-coupe-s111-2003-2008/38204d1276396353-vacuum-lines-2004-tiberon-pict0001.jpg

usually caused by busted diaphram in fuel pressure regulator allowing fuel to be drawn thru regulator directly to intake manifold. Pull vacuum line off regulator, plug line with golf tee, start car and watch to see if gas comes out of regulator. If yes, turn off car, replace regulator. The regulator sits near the fuel rail on the top of the engine as shown below. I will paste replacement instructions below from autozone.com in case you need to replace the regulator. Please let me know if you have any questions.

Removal & Installation

4.2L Engine

1. Relieve the fuel system pressure.
2. Remove the air cleaner outlet resonator.
3. Disconnect the engine wiring harness from the retaining clips at the front of the engine.
4. Disconnect the fuel pressure regulator vacuum line.
5. Clean any dirt from the fuel pressure regulator and the surrounding area.
6. Disconnect the fuel return pipe.
7. Remove the fuel return pipe retainer.
8. Remove the fuel pressure regulator retainer.
9. Remove the fuel pressure regulator.
10. Inspect the regulator filter screen for contamination. If contaminated, replace the fuel pressure regulator.

To install:

1. Install the regulator filter.
2. Install the new O-ring on the fuel pressure regulator.
3. Lubricate the fuel pressure regulator O-ring with clean engine oil.
4. Push the fuel pressure regulator into the regulator housing on the fuel rail.
5. Install the fuel pressure regulator retainer. Tighten the regulator retainer screw to 71 inch lbs. (8 Nm).
6. Install the fuel return pipe retainer. Tighten the return pipe retainer screw to 71 inch lbs. (8 Nm).
7. Connect the fuel return pipe.
8. Connect the fuel pressure regulator vacuum line.
9. Connect the negative battery cable.
10. Inspect for leaks:
    1. Turn ON the ignition for 2 seconds.
    2. Turn OFF the ignition for 10 seconds.
    3. Turn ON the ignition.
    4. Inspect for fuel leaks.
    
    
11. Install the engine wiring harness into the retaining clips at the front of the engine.
12. Install the air intake resonator.

easy,it's on the fuel rail,make sure that is the problem and not the pump,check fuel pressure before the regulator.











TIM..........

Sounds like you have fuel pressure bleeding off. Leaking fuel pressure regulators are really common on these. Fuel pumps can also cause this to happen. The first thing I would do is check fuel pressure. If it doesn't hold pressure than its leaking out the regulator or the check valve in the pump is bad.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Removal & Installation of fuel Regulators on
4.8L, 5.3L & 6.0L Engine To Remove:
CAUTION
Three styles of fuel pressure regulators and fuel rails will be used in this model year. Each regulator has a different "footprint" that consequently changes the size of the receiving port in the fuel rail. The regulator retaining clips are specific to each rail-regulator design and cannot be interchanged.

1. Remove the engine sight shield.
2. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure.
3. Clean the fuel pressure regulator retainer and the surrounding area.
4. Remove or disconnect the following:
   • Fuel pressure regulator vacuum line.
   • Fuel pressure regulator retainer.
   • Fuel pressure regulator.
5. Remove the following parts from the fuel rail:
   • Backup ring (10)
   • Regulator Seal O-ring (11)
   • Regulator filter (12)
   • Regulator seal O-ring (13)

To Install:

1. Make sure the NEW fuel pressure regulator retainer is the right one.
2. The tabs (1) are used on the straight vacuum port retainer (2), and the E85-straight vacuum port retainer (3).
3. The angle vacuum port retainer (4) has no tabs.
   
   
4. Install the following parts onto the fuel pressure regulator (9).
   • Backup ring (10)
   • Regulator seal O-ring (11)
   • Regulator filter (12)
   • Regulator seal O-ring (13)
5. Lubricate the fuel pressure regulator O-rings with clean oil.
6. Install the fuel pressure regulator and retainer. CAUTION
   Whenever the fuel pressure regulator is removed from the fuel rail NEW O-rings and a NEW retaining clip should be used on reinstallation.
   
7. Connect the vacuum line.
8. Tighten the fuel filler cap.
9. Use the following to inspect for leaks:
   • Turn ON the ignition, with the engine OFF, for 2 seconds.
   • Turn OFF the ignition for 10 seconds.
   • Turn ON the ignition, with the engine OFF.
   • Install the engine sight shield.

8.1L Engine To Remove:
Fuel pressure regulator vacuum line

1. Before servicing the vehicle refer to the precautions at the beginning of thjs section
2. Remove the fuel injector sight shield as needed
3. Relieve fuel system pressure (See: Fuel Pressure Relieving)
4. Disconnect the fuel pressure regulator vacuum line (A) 8.1L Fuel pressure regulator retainers
   
   
5. Clean any dirt from the fuel pressure regulator retainer and the surrounding area
6. Remove the fuel pressure regulator retainer (I)
7. Remove the fuel pressure regulator (H) from the fuel pressure regulator housing

To Install:
8.1L Fuel pressure regulator retainers

1. Install or connect the following:
   • Backup ring (J) on the fuel pressure regulator (H)
   • New large O-Ring (K) on the fuel pressure regulator
   • Regulator filter (L) on the fuel pressure regulator
   • New small O-Ring (M) on the fuel pressure regulator
2. Lubricate the fuel pressure regulator large O-Ring and the small O-Ring with clean engine oil
3. Push the fuel pressure regulator onto the regulator housing on the fuel rail
4. Install a new fuel pressure regulator retainer (I)
5. Install or connect the following:
   • Fuel pressure regulator vacuum line
   • Negative battery cable
6. Tighten the fuel filler cap
7. Inspect for leaks using the following procedure:
   • Turn on the ignition with the engine off for two seconds
   • Turn off the ignition for 10 seconds
   • Turn on the ignition with the engine off
   • Inspect for fuel leaks
8. Install the fuel injector sight shield
9. Road test the vehicle to check performance

There are 2 fuel lines connecting to the fuel injector rail. The larger line is the pressure line and the smaller line is the return line. The smaller line attaches to the fuel pressure regulator. You will notice that the regulator also has a vacuum line attached to it. If you are planning on changing it your self, let me know. There is a specific way to change it for safety reasons.
Let me know.
Regards,