No fuel pressure in injectors

Fuel from the pressure regulator can't enter the intake manifold with out passing through the injector first. That means that if you have a leak in the inlet manifold you have a leaking injector.
A fuel pressure regulator is no more than a controlled leak. You test pressure on the fuel rail, if you have pressure you have fuel to the injectors.
The regulator controls that pressure by controlling the return flow to the fuel tank. You are in trouble when a pressure regulator does not flow (leak) fuel from the pressure (fuel rail) and return ports.
To test weather a injector is leaking you remove it from the inlet manifold and pressurize the injector.

the function of a fuel regulator is to maintain sufficient pressure in the manifold for the correct operation of the injectors . Fuel pumps being gear driven pumps will produce excessive pressure that will overcome the injector settings and flood out the engine . Therefore when the fuel pressure reaches a pre-set value the regulator opens and lets excess fuel flow back to the tank. It is normally located in the fuel manifold either in the end or on the side and some have a vacuum hose attached to them

run fault codes and look for faulty injector/s. have a pressure test done on the fuel manifold and check for faulty pressure regulator and fuel pump. This misfiring on start up is an indication that the fuel manifold is loosing pressure on standing and there is air getting in to the injectors until the pressure is restored.

run fault codes and check for injector faults. Check the fuel manifold pressure as it may be a fuel pump, blocked filters or a faulty pressure regulator that is not allowing fuel for the injectors.

code p1155 refers to heated oxygen sensor(HOS)-RH front heater circuit malfunction==causes -wiring--HO2S-- ECM. Replace the oxygen sensor.
Code p1135 refers to heated oxygen sensor(HO2S) -LH front-heater circuit malfunction==causes --wiring--HO2S--air induction system--fuel pressure--injectors--ECM replace the o2 sensor and have a pressure test done on the fuel manifold to check for pump/regulator/ filter problems.

Check this procedure about V8 3.9L Fuel Injectors - Removal & Installation

1. Before servicing the vehicle, please familiarize yourself with safety procedures.
2. Relieve fuel system pressure.
3. Remove or disconnect the following:
   Negative battery cable Engine appearance covers Fuel lines Fuel pressure regulator Fuel cross over elbow Fuel injector connectors Fuel injector clamping plates Fuel injectors

To install:

1. Install or connect the following:
   Fuel injectors. Use new O-ring seals. Fuel injector clamping plates Fuel injector connectors Fuel cross over elbow Fuel pressure regulator Fuel lines Engine appearance covers Negative battery cable
2. Start the engine and check for leaks.
   

1. Before servicing the vehicle, please familiarize yourself with safety procedures.
2. Disconnect the negative battery cable.
   CAUTION The engine appearance cover is equipped with a noise suppressor. If the noise suppressor becomes separated from the engine appearance cover it must be positioned on the intake manifold prior to installing the engine appearance cover.
3. Remove the engine appearance cover and the noise suppressor, if detached.
4. Remove the air cleaner outlet pipe.
5. Release the fuel system pressure.
6. Remove the four engine appearance cover mounting bracket nuts and the brackets.
7. Disconnect the fuel pressure sensor electrical connector from the sensor.
8. Disconnect the fuel pressure sensor vacuum connector from the sensor.
9. Disconnect the eight fuel injector electrical connectors from the injectors.
10. Disconnect the fuel temperature sensor electrical connector from the sensor.
11. Disconnect the fuel supply tube retaining clip from the fuel injection supply manifold.
12. Disconnect the fuel supply tube spring lock coupling.
13. Remove the four bolts and the fuel injection supply manifold and fuel injectors as an assembly.
14. Remove the fuel injectors from the fuel injection supply manifold.
    CAUTION Use O-ring seals that are made of special fuel-resistant material. Use of ordinary O-ring seals can cause the fuel system to leak. Do not reuse the O-ring seals.
15. Remove and discard the 16 O-ring seals from the fuel injectors.
    
    
    

    Fig. Exploded view of the fuel injector mounting-3.9L engine shown
    

To install:

1. Lubricate the new fuel injector O-ring seals with clean engine oil before installing.
   CAUTION Use O-ring seals that are made of special fuel-resistant material. Use of ordinary O-rings can cause the fuel system to leak. Do not reuse the O-ring seals.
2. Install sixteen new O-ring seals onto the fuel injectors. Lubricate the O-ring seals with clean engine oil prior to installation.
3. Install the fuel injectors and clips onto the fuel rail.
4. Install the fuel rail and injectors as an assembly. Tighten the fuel rail bolts to 89 inch lbs. (10 Nm).
5. Install the remaining components in the reverse order of removal.

Keep us updated.

You didn't post the size of your engine so please pick the appropriate one:

3.8L

1. Relieve the fuel system pressure.
   
2. Drain the cooling system.
   

1. Remove or disconnect the following:
2. Negative battery cable
   

• Supercharger
  
• Thermostat housing
  
• Exhaust Gas Recirculation (EGR) tube at the intake manifold
  
• Engine Control Temperature (ECT) sensor
  
• Intake manifold
  

To install:

1. Install or connect the following:
   
   • Intake manifold with new gaskets. Torque the bolts, working from the center out, to 11 ft. lbs. (15 Nm).
     
   • ECT sensor connector
     
   • EGR tube to the intake manifold
     
   • Thermostat housing
     
   • Supercharger
     
   • Negative battery cable
     
2. Refill and bleed the cooling system.
   
3. Run the engine and check for leaks and proper engine operation.
   

4.6L
4.6L Engine

1. Remove the brake booster hose from the throttle body.
   
2. Remove the fuel pressure regulator vacuum tube from the fuel pressure regulator and the water crossover.
   
3. Remove the PCV fresh air feed tube from the camshaft cover and the throttle body.
   
4. Remove the PCV dirty air tube from the PCV orifice in the right camshaft cover and from the intake manifold.
   
5. Disconnect the fuel injector electrical connectors from the fuel injectors.
   
6. Remove the fuel injector wiring harness.
   
7. Remove the fuel rail bracket nut from the engine lift bracket.
   
8. Remove the fuel rail studs.
   
9. Lift and remove the fuel rail with injectors.
   
10. Loosen the plenum duct clamp in order to remove the intake manifold.
    
11. Remove the intake manifold bolts.
    
12. Remove the intake manifold.
    

To install:

1. Install the intake manifold, fitting the plenum duct over the intake manifold duct.
   
2. Loosely install the intake manifold bolts.
   

// // 0) preLoad.src = ctl00_cphLeft_chRepairTreeNav_tvTOC_ImageArray[i]; } ctl00_cphLeft_chRepairTreeNav_tvTOC_Data.lastIndex = 45; ctl00_cphLeft_chRepairTreeNav_tvTOC_Data.populateLog = theForm.elements['ctl00_cphLeft_chRepairTreeNav_tvTOC_PopulateLog']; ctl00_cphLeft_chRepairTreeNav_tvTOC_Data.treeViewID = 'ctl00$cphLeft$chRepairTreeNav$tvTOC'; ctl00_cphLeft_chRepairTreeNav_tvTOC_Data.name = 'ctl00_cphLeft_chRepairTreeNav_tvTOC_Data'; //]]> var _strTreeScrollHidName = 'ctl00_hidTreeScrollPos';

Intake manifold torque sequence-4.6L engine

2. Tighten the intake manifold bolts in sequence. Tighten the intake manifold bolts to 89 inch lbs. (10 Nm).
   
4. Tighten the plenum duct clamp to the intake manifold. Tighten the plenum duct clamp to 24 inch lbs. (2.75 Nm).
   
5. Inspect the fuel injector O-rings. Ensure the fuel injector O-rings are not missing, misaligned or damaged. Replace the O-rings if necessary.
   
6. Lubricate the intake manifold fuel injector bores with light mineral oil (GM P/N 9981704), clean engine oil, or equivalent.
   
7. Install the fuel rail with fuel injectors as an assembly.
   
8. Install the fuel rail studs. Tighten the fuel rail studs to 80 inch lbs. (9 Nm).
   
9. Install the fuel rail bracket nut to the engine lift bracket. Tighten the fuel rail bracket nut to 89 inch lbs. (10 Nm).
   
10. Install the fuel injector wiring harness.
    
11. Connect the fuel injector electrical connectors to the fuel injectors.
    
12. Install the PCV dirty air tube to the PCV orifice in the right camshaft cover and to the intake manifold.
    
13. Install the PCV fresh air feed tube to the camshaft cover and the water crossover.
    
14. Install the fuel pressure regulator vacuum tube to the fuel pressure regulator and the throttle body.
    
15. Install the brake booster hose to the throttle body.
    

Failure-to-start scenarios are often an issue of "fuel or spark?"

To check fuel pump, install a fuel pressure gauge on the Shrader valve connector on the
fuel rail, reading ???? - I couldn't find the spec for nominal fuel pressure.....

One good source of diagnostic info is your car's computer - commect an OBD-II code
reader to your car's OBD-II port and ask the car what it thinks it wrong - its capable of
posting 100s of possible error codes, any number of which would/could implicate a fuel
system component. Here a (very) short list of possible computer codes your car's computer
may currently be posting:

error code meaning
--------------- -------------
P0107 MAP (manifold absolute pressure) sensor - low input (to computer)
P0108 MAP (manifold absolute pressure) sensor - high input (to computer)
P0122 TP (throttle position) sensor - low input (to computer)
P0123 TP (throttle position) sensor - high input (to computer)
P0171 fuel system lean
P0172 fuel system rich
P0201 fuel injector 1 control circuit malfunction
P0202 fuel injector 2 control circuit malfunction
P0203 fuel injector 3 control circuit malfunction
P0204 fuel injector 4 control circuit malfunction
P0300 multiple engine misfire detected
P0301 cylinder 1 misfire detected
P0302 cylinder 2 misfire detected
P0303 cylinder 3 misfire detected
P0304 cylinder 4 misfire detected
P0336 CPS (crankshaft position sensor) range/performance
P06xx control module (computer) failure


Possible bad parts:
TP (throttle position) sensor - Duralast TPS172 $51.99 at www.autozone.com

Fuel pressure regulator:
www.autozone.com/autozone/regairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f8036e816

Fuel Pump:
www.autozone.com/autozone/repairinfo/repairguide/repairGuideContect.jsp?pageId=0996b43f8036e7c7

Fuel Filter:
www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f8036e787

Fuel rail (supply manifold) and fuel injectors:
www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f8036e7a0

Could also be dying fuel pump relay - Duralast 19264 $14.99 at www.autozone.com.
I don't work for Autozone.com - just convenient info for some cars.

Autozone.com will expect you to register (free) to access their repair guide database (which has pictures - especially helpful for finding sensors).

The Vortec engines were notorious for those kind of problems. The problem will be under the upper-intake manifold, and the fuel injector assembly will either have a cracked plastic fuel line running out to one or more of the fuel injectors, or the fuel pressure regulator that is located on the end of the fuel injector assembly is faulty or it has detached from the fuel injector assembly. Either way the lower intake manifold will be flooded with fuel anytime that the fuel pump runs.

There were two types made, the first type had fuel lines that connected to the lower intake manifold, and then from the metal fittings the fuel line turns into plastic and runs inside the lower intake manifold and under the upper-intake manifold where it runs over to the fuel injector assembly, and this type can really flood out an engine when it becomes faulty.

The second type had metal fuel lines running over the upper intake manifold and they connected to the top of the fuel injector assembly, however, under the upper-intake manifold there are still plastic lines to the fuel injectors and also the fuel pressure regulator that could be faulty and cause the engine to severely flood.

The upper-intake manifold is not that difficult to remove, and after you remove the upper-intake manifold then (replace the fuel lines to the fuel injector assembly if it is the second type) turn the ignition to the "Run" position and when the fuel pump runs you should see where the fuel is leaking/spraying from, and it will most likely be a large high pressure leak from a ruptured plastic fuel line.

Let me know if you require any further assistance.

GM Century/Lumina/Grand Prix/Intrigue 1997-2000
Fuel Pressure Regulator - Removal & Installing
The fuel pressure regulator is a diaphragm-operated relief valve with fuel pump pressure on one side and regulator spring pressure and intake manifold vacuum on the other side. The regulator's function is to maintain a constant fuel pressure across the injectors at all times. The pressure regulator compensates for engine load by increasing fuel pressure as engine vacuum drops.

The fuel pressure regulator is serviced as a separate component. When servicing the pressure regulator, make sure that the O-ring back-up, large O-ring, filter screen and small O-ring are properly positioned on the pressure regulator.


Fig. Cutaway view of a typical fuel pressure regulator


REMOVAL & INSTALLATION
The need to work as cleanly as possible cannot be over-emphasized. Even the smallest amount of dirt, if allowed into the fuel pressure regulator and/or the fuel rail, will find its way to the fuel injectors. The nozzle openings of the injectors are very small. Keep hands and tools clean. Clean the areas to be disconnected with a suitable solvent. Carefully cover open fittings and connections to keep out foreign material. Dirt in the injectors almost guarantees a clogged fuel injector and engine performance problems.
3.1L and 3.4L (VIN E) Engines

1. Disconnect the negative battery cable.
2. Relieve the fuel system pressure using the procedures found in this section.
3. Remove the upper intake manifold assembly. Please see .
4. Disconnect the vacuum line from the pressure regulator.
5. Remove the regulator retaining screw and remove the retainer bracket. Using a clean shop cloth to catch fuel spillage, carefully pull the regulator from the fuel rail. Twist the regulator slightly while removing to ease removal. Discard the O-ring.

Fig. Exploded view of the fuel pressure regulator mounting-3.1L and 3.4L (VIN E) engines
To install:

1. Clean all parts well. DO NOT use shop compressed air to test or clean a fuel pressure regulator. Clean the fuel pressure regulator screen, if necessary. DO NOT immerse the fuel pressure regulator in a solvent bath or it will be damaged.
2. If the filter screen has been contaminated, it should be removed and the pressure regulator replaced.
3. Lubricate a new pressure regulator O-ring with clean engine oil and install on the regulator inlet.
4. Install the fuel return pipe to the regulator.
5. Install a new retainer and spacer bracket into the slot on the fuel rail and install the pressure regulator to the fuel rail. Tighten the fuel return line nut to 13 ft. lbs. (17 Nm).
6. Connect the vacuum line to the pressure regulator and install the retainer screw. Tighten to 76 inch lbs. (8.5 Nm).
7. Inspect and verify that the retainer and spacer bracket is engaged in the slots in the fuel rail. Grasp and pull on the regulator to ensure that it is properly seated.
8. Install the upper intake manifold. Please see .
9. Connect the negative battery cable.
10. Inspect for leaks using the following procedure:
    • Turn the ignition switch to the ON position for 2 seconds.
    • Turn the ignition switch to the OFF position for 10 seconds.
    • Turn the ignition switch to the ON position again.
    • Inspect all areas for fuel leaks.

Other size engine can find in autozone.com (free register).

Hope this help (remember rated this).