Fuel pump testing

Hi Chrystal ,what make , model and year vehicle do you have ? Plus what engine does it have . I take it it did not start before the new fuel pump ? What ,did someone tell you it could be the fuel pump ? Without testing fuel pump pressure an fuel pump electrical circuit testing no one you say it needs a fuel pump . You probably have no clue about testing automotive fuel systems or electrical systems . Your best bet , have it towed to a qualified repair shop. It takes years for qualified tech's to learn these thing's . What makes you want to be's think you can do it without any training ? You probably didn't need a fuel pump in the first place .

Does your truck have duel tanks ?

You need to know the fuel pressure. Just turning the key to on should cause the fuel pump to put high pressure in the fuel line to the engine and fuel injectors. If the pump doesn't turn on, there is an Inertia fuel shutoff switch in the power line going to the pump, so check that has not tripped.

If hard starting or running poorly problems, you could have a fuel pump that still works but fails to keep adequate pressure- a weak pump that needs replacing. If your Mazda has a fuel pressure test port, called a shrader valve, it is easy to hook up a fuel pressure test gauge to check fuel pressure. Autozone and maybe other national stores rent or loan fuel pressure testers.

1.6L DOHC (same way as the ISUZU impulse ) same car.
4XE1 engine twin cam.
has MPI injection with fuel rail, regulator and loop
disconnecting the feed line and stuffing it with guage only does 1 of 5 tests. done on MPI. it does JUST the shut test.
the correct way it to check it at the filter or rail tests ports on most cars.
in some cases you must add it.
they sell banjo fittings with test ports at summit racing dot com.
so the first question on all MPI cars, is , where is the stock fittings.
other cars the rail has a schrader valve or a plugged hole to add one. (test port) did you look first for this?
to test the FPR, unplug the vacuum line running
and pressure will jump up 6 to 10 psi.
this simulates wide open throttle pressure, a key fact in getting full power from engine, i test cranking presssure, idle, 3000rpm
and wot pressures to be sure the PFR is working, not just the pump.



the spec at the rail is.

Late 1986 to 1993 I-TEC MPFI system (after VIN 0908197)
Regulator vacuum line connected-36 psi
Regulator vacuum line disconnected-42.5 to 45 psi

the shunt test can hit 60 pis easy. do so for only 5sec.
as this stresses the pump .

the only rail drawing , shows no fittings (cheap buggers)



not even a cheap plug...

below is the twin cam, 1.6L
buy a TEE feeting, and put it at upper, red arrow.
use clamps rated for fuel injection, not chezzy screw band clamps as seen on carb cars. use the correct parts.
or you will get leak and it will not be pretty,
the filter as at 14 ID. this is the pressure feed side of the loop.
30 to 60psi , so all parts must be rated over 60, psi, (100psi is a nice goal)



now the words directly from the IMPULSE FSM.

Testing

1. Relieve the fuel pressure.
2. Disconnect the fuel line near the engine and install fuel pressure gauge T-connector in the line.
3. Connect the fuel pressure gauge to the T-connector.
4. Start the engine and check the fuel pressure, it should be:
5. 4XC1-Turbo and DOHC I-Mark, G200Z Impulse: 35.6 psi with the vacuum hose of the pressure regulator disconnected and plugged. 28.4 psi with the vacuum hose connected and at idle.
6. 4ZC1-Turbo, 4ZD1 Impulse and 4ZE1 engine: 42.6 psi with the vacuum hose at the pressure regulator disconnected and plugged. 35.6 psi with the vacuum hose connected at idle. Disconnect the VSV before checking pressure.
7. V6 engine: 9.13 psi at the fuel pressure line after the fuel filter.
8. 4XE1 SOHC and DOHC engine: Flow test, disconnect the hose from the EFI fuel feed line at the engine and place in a suitable container. Apply battery voltage to the fuel pump. Pump should supply 1/4 quart (0.24L) within 15 seconds. Pressure test, connect a pressure gauge in the fuel pressure line after the fuel filter, located at the driver's side frame rail. Disconnect the vacuum hose from the pressure regulator. Apply battery voltage to the pump. After the pump stabilizes, the pressure should be 35-38 psi (245-256 kPa) and hold steady.

Is there a pump in the tank ?. I am not familiar with this car, but I had a similar problem with my Citroen Diesel, /Peugeot simila. and the low pressure pump in the Fuel tank had failed. In the car stated the tank is under the rear seat, and entry can be gained to the tank/pump from here

If you know for a fact the pump is getting power and ground, and nothing is coming out of the line before the filter, then yes the line could be clogged up.

Check fuel pressure at test port, fuel filter and inspect the whole fuel line for kinks & crimps. If that doesn't work disconnect the fuel filter then use high pressure air to blow from the pressure regulator to the removed filter to ensure that the line is clear and open. Hook everything back up and check for pressure.

Well, the fuel pump relay may not be getting electricity to the fuel pump.

Also, use the following procedure to test the fuel pump before changing it again:

TESTING Fig. 1: Connect the fuel pressure gauge C4799B or equivalent to the fuel rail service valve - 3.3L shown
Fig. 2: Checking the fuel pressure with a gauge - 3.5L shown
Fig. 3: Checking the pressure between the pump and the filter
Fig. 4: Place the other end of the adapter 6668 into an approved gasoline container

1. Release the fuel system pressure as described in earlier in this section.
2. Remove the protective cover from the service valve on the fuel rail.
3. Connect fuel pressure gauge C-4799B or equivalent to the fuel rail service valve.
4. Place the ignition key in the ON position. Using the DRB III tester or equivalent, access the ASD fuel system test. (The ASD fuel system test will activate the fuel pump and pressurize the system.)
5. If the gauge reading equals the specifications, then further testing is not required. Without vacuum applied to the regulator, the 3.3L engine fuel system operates at 55 psi (379 kPa). With the engine idling and the manifold vacuum applied to the regulator, the system operates at approximately 46 psi (317 kPa). Without vacuum applied to the regulator, the 3.5L engine fuel system operates at 48 psi (331 kPa). With the engine idling and the manifold vacuum applied to the regulator, the system operates at approximately 39 psi (269 kPa). The fuel system pressure varies with the different amounts of manifold vacuum applied to the regulator. If the pressure is not correct, record the pressure and remove the gauge.
6. Ensure that the fuel does not leak from the fuel rail service valve. Install the protective cover onto the fuel rail service valve.
7. If the fuel pressure reading was below the specifications, test the system according to the following procedure:
   1. Perform the fuel pressure release procedure.
   2. Install a fuel gauge C4799 and fuel adapter 6631 or equivalent in the fuel supply line between the tank and the fuel filter.
   3. Using the DRB III scan tool or equivalent, with the ignition key in the ON position, repeat the ASD fuel system test.
8. If the pressure is at least 5 psi (1 kPa) or higher than the reading recorded, replace the fuel filter.
9. If no change is observed, gently squeeze the return hose. If the pressure increases, replace the pressure regulator. If the gauge reading does not change when the return hose is squeezed, the problem is either a plugged inlet strainer or defective fuel pump.
10. If the fuel pressure reading was above the specifications test the system according to the following procedure:
    1. Perform the pressure release procedure.
    2. Install fuel pressure gauge C4799 and adapter 6631 or equivalent in the fuel supply line between the fuel tank and the fuel filter.
    3. Remove the fuel return line hose from the pump at the tank. Connect pressure test adapter 6668 or equivalent to the return line. Place the other end of adapter 6668 into an approved gasoline container. A minimum of 2 gallon tank should be sufficient. All return fuel will flow into the container.
    4. Using the DRB III scan tool or its equivalent, with the ignition key in the ON position, repeat the ASD fuel system test.
11. If the pressure is now correct, replace the fuel pump.
12. If the pressure is still above specifications, remove the fuel return hose from the chassis fuel tubes (at the engine) and attach fuel pressure test adapter 6668 or equivalent to the return tube. Place the other end of the hose in the clean container, repeat the test. If the pressure is now correct, check for a restricted fuel return line. If there is no change observed, replace the fuel pressure regulator.

Fuel Pressure RegulatorREMOVAL & INSTALLATION
(see Figure 1)

1. Properly relieve the fuel system pressure and disconnect the negative battery cable.
2. Disengage the vacuum line from the pressure regulator.
3. If applicable, disengage the fuel line(s) from the regulator.
4. Remove the retaining bolts, then separate the regulator from the fuel rail assembly.

To install:

1. Install the regulator to the fuel rail and secure using the retaining bolts.
2. If applicable, engage the fuel line(s) to the regulator.
   

Fig. 1: Cross-sectional view of the fuel pressure regulator

1. Engage the regulator vacuum hose.
2. Connect the negative battery cable, then pressurize the fuel system by cycling the ignition (without attempting to start the engine) and check for leaks.

To determine if the pump is in good condition, tests for both volume and pressure should be performed. The tests are made with the pump installed, and the engine at normal operating temperature and idle speed. Never replace a fuel pump without first performing these simple tests.
Be sure that the fuel filter has been changed at the specified interval. If in doubt, install a new filter first. The filter is an inexpensive maintenance item and should be replaced if old or suspect. Start the tests with a visual inspection. Check lines for damage, kinks or restrictions. Make sure all fittings are properly tightened and that there is no leakage from the system.

Pressure Test

1. Disconnect the fuel line from the carburetor and connect a fuel pump pressure gauge.
2. Start the engine and check the pressure with the engine at idle. If the pump has a vapor return hose, squeeze it off so that an accurate reading can be obtained. Pressure should not be below specification. Most of the carbureted engines covered by this manual are specified between 3-7 psi. Refer to the Tune-Up Specifications chart in Chapter 2 of this manual.
3. If the pressure is incorrect, replace the pump. It if is OK, perform the volume test.
   

Volume Test

1. Disconnect the fuel feed line from the carburetor.
2. Place the fuel line into a graduated container.
3. Run the engine at idle until one pint of gasoline has been pumped. One pint should be delivered in 30 seconds or less. There is normally enough fuel in the carburetor float bowl to perform this test, but refill it, if necessary.
4. If the delivery rate is below the minimum, check the lines for restrictions or leaks. If none are found, replace the pump.

Hope this helped.

The best way to find out is, have a fuel pressure test done, that will reveal a weak pump or not.