No try taping the gauge to your windshield and take your car for a spin and record what is does at each rpm. If you get a sudden drop that takes a while to recover then it's fuel pressure. If it recovers fast then your pump and regulator are fine.

When did you start to notice this loss in power? Was it after changing everything?

 

it was previous/during to changing everything, which is why i had started doing a tune up. unfortunately my gauge hose is about a foot long so not sure how i can place it somewhere i can see while driving. im thinking pressure is strong if not high since the motor doesnt stammer at take off or at wot. the past week or 2 the fuel gauge has been reading more off then usual, could these two issues be related? right now im at 114 miles but the gauge is at 1/4, this is from a full tank.

 

anyone??

last night when i was driving and come to a stop sign i could feel a shake like a miss, but when im on the gas its not there

 

How was the back pressure before the cats measured? I have never heard of that before? This sounds like bad cat to me. Loss of power, slight miss but nothing else seems wrong. The fuel level sensor does not effect the performance of the engine what so ever... These are not the highest quality senders but I have seen worse. I would fill the car up and see just how many gallons you used in the 114 miles. If it is a 1/4 tank for sure then you do have mileage issues. Again a plugged cat can kill your mileage really fast.

Massey

 

gorn had told me one time take out the o2 sensors before the cat and plug a vacc/pressure gauge in there and if its more than 3 psi then cats are gone, mine was a little more than 1 psi

 

Isnt one psi and higher a bad cat?

 

I thought it was 2psi or higher is bad. filled up the tank at 139 miles when the needle was just over the empty, 12.6 gallons. works out to be 11 mpgs all city. normally when its just over empty and i fill it, it goes 14.xx gallons, what you guys think?

 

This might help, straight from GM:

Document ID# 724504
2002 Chevrolet Camaro
Fuel System Diagnosis

System Description

When you turn ON the ignition switch, the control module enables the fuel pump relay which powers the fuel pump ON. The fuel pump remains ON as long as the engine is cranking or running and the control module receives ignition reference pulses. If there are no ignition reference pulses, the control module shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops.

The fuel tank stores the fuel supply. The electric fuel pump supplies fuel through an in-line fuel filter to the fuel injection system. The pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pressure regulator maintains the correct fuel pressure to the fuel injection system. A separate pipe returns unused fuel to the fuel tank.

Test Description

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

This step verifies that the fuel pump is operating.

This step tests for an internal fuel leak. If the fuel pressure decreases during this test, an internal loss of pressure is indicated.

This step tests the fuel pressure regulator. The fuel pressure regulator is controlled by engine vacuum. With engine vacuum applied, the pressure should decrease by the specified value.

This step inspects the fuel pressure regulator for a fuel leak from the vacuum port. If fuel leaks from the vacuum port of the fuel pressure regulator while the fuel pump is commanded ON, replace the fuel pressure regulator.

This step tests for a loss of fuel pressure between the fuel pump and the shut-off adapter on the fuel feed pipe.

This step tests for a leaking fuel injector, or fuel pressure regulator. If the fuel pressure remains constant during this test, the fuel injectors are not leaking fuel.

This step tests for a restricted fuel return pipe. If the fuel pressure is within the specified values, a restriction in the fuel return pipe is indicated.

This step determines if the fuel pressure regulator, or the fuel pump, is the cause of the low fuel pressure. If the pressure rises above the specified value, the fuel pump is OK.

This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.

Step

Action

Value

Yes

No

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2


Important

Inspect the fuel system for damage, or external leaks before proceeding with this diagnostic.

Turn ON the ignition, with the engine OFF.
Command the fuel pump ON with a scan tool.
Does the fuel pump operate?

--

Go to Step 3

Go to Fuel Pump Electrical Circuit Diagnosis

3


Important

Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic test.

Turn OFF the ignition.
Turn OFF all accessories.
Install the Fuel Pressure Gage. Refer to Fuel Pressure Gage Installation and Removal .
Turn ON the ignition, with the engine OFF.

Important

The fuel pump may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
DO NOT start the engine.
Command the fuel pump ON with a scan tool.
Observe the fuel pressure gage with the fuel pump commanded ON.
Is the fuel pressure within the specified value?

334-375 kPa (48-54 psi)

Go to Step 4

Go to Step 12

4


Important

The fuel pressure may vary slightly if the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

Monitor the fuel pressure gage for 1 minute.

Does the fuel pressure decrease by more than the specified value?

34 kPa (5 psi)

Go to Step 9

Go to Step 5

5

Relieve the fuel pressure to the first specified value.
Monitor the fuel pressure gage for 5 minutes.
Does the fuel pressure decrease by more than the second specified value?

69 kPa (10 psi)

14 kPa (2 psi)

Go to Step 24

Go to Step 6

6

Turn OFF the ignition for 15 seconds.
Turn ON the ignition, with the engine OFF.
Monitor the fuel pressure gage.
Start the engine.
Does the fuel pressure decrease by the specified value after the engine starts?

21-69 kPa (3-10 psi)

Go to Step 7

Go to Step 8

7

Operate the vehicle within the conditions of the customer's concern.
Monitor the fuel related parameters with a scan tool.
Do any of the scan tool parameters indicate a lean condition?

--

Go to Step 17

Go to Symptoms - Engine Controls

8

Disconnect the vacuum hose from the fuel pressure regulator.
Monitor the fuel pressure gage.
Idle the engine.
Apply 12-14 inches of vacuum to the fuel pressure regulator with a hand held vacuum pump.
Does the fuel pressure decrease by the specified value when the vacuum is applied?

21-69 kPa (3-10 psi)

Go to Step 21

Go to Step 23

9

Turn OFF the ignition.
Remove the vacuum hose from the fuel pressure regulator.
Turn ON the ignition, with the engine OFF.
Command the fuel pump ON with a scan tool.
Inspect for a fuel leak from the vacuum port of the fuel pressure regulator.
Is the fuel pressure regulator leaking fuel?

--

Go to Step 23

Go to Step 10

10

Turn OFF the ignition.
Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure .
Disconnect the fuel feed hose and the fuel return hose from the fuel rail pipes. Refer to Quick Connect Fitting(s) Service (Metal Collar) .
Install the J 37287 Fuel Pipe Shut-off Adapters between the fuel pipe between the fuel hoses and the fuel rail pipes.
Open the valves on the shut-off adapters on the fuel pipe.
Turn ON the ignition, with the engine OFF.
Command the fuel pump ON with a scan tool.
Bleed the air from the fuel pressure gage.
Command the fuel pump ON and then OFF with a scan tool.
Close the shut-off valve on the fuel feed pipe.
Monitor the fuel pressure gage for 1 minute.
Does the fuel pressure remain constant?

--

Go to Step 19

Go to Step 11

11

Turn OFF the ignition.
Open the shut-off valve on the fuel feed pipe.
Turn ON the ignition, with the engine.
Command the fuel pump ON and then OFF with a scan tool.
Close the shut-off valve on the fuel return pipe.
Monitor the fuel pressure gage for 1 minute.
Does the fuel pressure remain constant?

--

Go to Step 23

Go to Step 20

12

Is the fuel pressure more than the specified value?

375 kPa (54 psi)

Go to Step 14

Go to Step 13

13

Is the fuel pressure more than the specified value?

0 kPa (0 psi)

Go to Step 16

Go to Step 17

14

Turn OFF the ignition.
Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure .
Disconnect the fuel return hose from the fuel rail pipe. Refer to Quick Connect Fitting(s) Service (Metal Collar) .
Attach a length of a flexible fuel hose to the fuel rail outlet passage.
Place the open end of the flexible fuel hose into an approved gasoline container.
Turn ON the ignition, with the engine OFF.
Monitor the fuel pressure gage with the fuel pump operating.
Is the fuel pressure within the specified value?

334-375 kPa (48-54 psi)

Go to Step 22

Go to Step 15

15

Inspect the fuel rail return pipe and the fuel rail outlet passage for a restriction.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 23

16

Turn OFF the ignition OFF.
Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure .
Disconnect the fuel return hose from the fuel rail pipe. Refer to Quick Connect Fitting(s) Service (Metal Collar) .
Install the J 37287 between the fuel return pipe and the fuel rail.
Open the valve in the fuel pipe shut-off adapter.
Turn ON the ignition, with the engine OFF.
Bleed the air from the fuel system.
Monitor the fuel pressure gage.

Notice

DO NOT allow the fuel pressure to exceed 517 kPa (75 psi). Excessive pressure may damage the fuel system.

Slowly close the valve in the fuel return pipe shut-off adaptor.
Command the fuel pump ON with a scan tool.
Does the fuel pressure increase to more than the specified value?

375 kPa (54 psi)

Go to Step 23

Go to Step 17

17

Inspect the following components for a restriction:

The fuel filter
The fuel feed pipe
Did you find and correct the condition?

--

Go to Step 25

Go to Step 18

18

Inspect the harness connectors and the ground circuits of the fuel pump for poor connections. Refer to Testing for Intermittent and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 19

19

Remove the fuel sender assembly. Refer to Fuel Sender Assembly Replacement .
Inspect the following items:
The flexible hose of the fuel pump for damage
The harness connectors on the in-tank fuel pump for poor connections
The fuel strainer for a restriction
The fuel tank for contamination
Did you find and correct the condition?

--

Go to Step 25

Go to Step 24

20

Turn OFF the ignition.
Raise the fuel rail without removing the fuel lines. Refer to Fuel Rail Assembly Replacement .
Turn ON the ignition, with the engine OFF.
Command the fuel pump ON with a scan tool.
Locate and replace the leaking fuel injector. Refer to Fuel Injector Replacement .
Did you complete the replacement?

--

Go to Step 25

--

21

Repair the vacuum source to the fuel pressure regulator.

Did you complete the repair?

--

Go to Step 25

--

22

Locate and repair the restricted fuel return pipe.

Did you complete the repair?

--

Go to Step 25

--

23


Important

Before replacing the fuel pressure regulator, inspect for a missing or for a damaged O-ring seal.

Replace the fuel pressure regulator. Refer to Fuel Pressure Regulator Replacement .

Did you complete the replacement?

--

Go to Step 25

--

24

Replace the fuel pump. Refer to Fuel Sender Assembly Replacement .

Did you complete the replacement?

--

Go to Step 25

--

25

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3

Document ID# 724504
2002 Chevrolet Camaro

 

Thank you Liberty that is the flow chart I was trying to quote from by memory and it has been over 10 years since I last looked at it.

Massey

 

wow now theres a diagnostic! only trouble is i dont have a scan tool to control the pump on/off. correct me if im wrong but ls1 cars dont have return lines? and the regulator is IN the tank, right? theres a fat wire harness on the underside of the car, looks like it goes to the tank but mounted on the body, does that have any say in the incorrect gauge? what numbers are normal spec for vaccum at idle?