No fuel pressure when parked in garage in 03. 08 replaced sending unit and pump, drained tank, new fuel. Still no fuel pressure at throttle body. is there a wiring problem or selenoid issue? car has 250000 miles. has been parked since 2003.
Sounds sort of like a map sensor or the heating and cooling sensor. Both help regulate the fuel. also need to check to see if the thermastat is stuck to open. If the hot and cold sensor is giving a false reading of hot to the computer this can cause the car not to pump fuel. If the sensor is bad also replace the therm as well.
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1. Remove negative battery cable 2. Relieve fuel pressure (See Fuel Pressure Relief below) 3. Remove fuel filler neck 4. Disconnect fuel lines and electrical connection at fuel tank unit 5. Remove bolts from fuel tank mounting straps and lower fuel tank 6. Remove fuel level sending unit and fuel pump retaining bolts or cam lock ring 7. Remove fuel pump and sending unit from fuel tank 8. Pull fuel pump upward while pulling away from bottom support (be carefull not to damage the rubber insulator unless your fuel pump kit comes with a new one.) 9. Disconnect wire connectors from fuel pump. 10. Reverse procedure to install.
to replace the fuel pump module.first you need to relieve the fuel system pressure.turn off radio first, then disconnect the negative battery cable.drain fuel from fuel tank.then then safely raise support car on jack stands. make sure sitting on solid level ground then remove the fuel charcoal canister hoses and vent line remove disconnect fuel pump. disconnect fuel pump electrical connector and remove fuel filler hose from fuel tank then remove the fuel tank from the vechicle.the heat shield and the rear exhaust system may have to be remove if you problem dropping the fuel tank.once fuel tank dropped you need snap ring pliers to remove the fuel pump module retaining ring.disconnect the fuel pump sending unit.disconnect the fuel pressure sensor and fuel pump module electrical connector .if you need help to replace the fuel level sending unit.you need a haynes repair manual.it has instruction how to remove and replace the fuel level sending unit.but most of the time the whole new fuel pump module come with new fuel level sending unit.if you are replacing fuel pump.when done put every thing back visa versa. be very careful working around gasoline and fuel tank.dont smoke.becareful dont make no sparks with wrenches when removing gas tank.wear safety glasses and have a helper at all times. dont work under vechicle by your self.
The fuel pump is part of the fuel sender assembly located inside the fuel tank.
Release the fuel system pressure and disconnect the negative battery cable.
Drain the fuel tank, then raise and safely support the vehicle.
Remove the fuel tank from the vehicle.
Clean the area surrounding the sender assembly to prevent contamination of the fuel system.
To remove the fuel sender from the tank, remove the fuel sender
assembly nuts and retaining ring. Carefully remove the sending unit from
the fuel tank. Discard the O-rings.
If necessary, separate the fuel pump from the sending unit assembly.
If removed, install the fuel pump to the sending unit. If the strainer was removed, it must be replaced with a new one.
Inspect and clean the O-ring mating surfaces.
Install a new O-ring in the groove around the tank opening. If applicable, install a new O-ring on the fuel sender feed tube.
Install the fuel sender assembly as follows:
The fuel pump strainer must be in a horizontal position, and when
installed, must not block the travel of the float arm. Gently fold the
strainer over itself and slowly position the sending assembly in the
tank so the strainer is not damaged or trapped by the sump walls.
Install the retaining ring and nuts, then tighten the nuts to 63 inch lbs. (7 Nm).
Install the fuel tank assembly.
Lower the vehicle.
Fill the fuel tank, tighten the fuel filler cap and connect the negative battery cable.
Turn the ignition switch to the
position for 2 seconds,
for 10 seconds, then back to the
position. Check for fuel leaks.
Relieve the fuel system pressure and check that there is an adequate quantity of fuel in the tank.
Connect a fuel pressure gauge to the pressure connector fitting
located on the end of the fuel rail. On 5.7L engines, it is located
inline shortly before the fuel rail and accumulator.
Make sure the ignition switch has been in the
position for at least 10 seconds and that all accessories are OFF.
Turn the ignition switch
and the pump will run for about 2 seconds. Note the system
pressure with the pump running, it should be between 40-47 psi.
The ignition switch may have to be cycled to the ON
position more than once to obtain maximum pressure. It is also normal
for the pressure to drop slightly when the pump first stops, but it
should then hold steady.
If the pressure is not as specified, verify that fuel pump operation is heard in the tank.
If fuel pump operation is not heard, inspect the fuel pump relay and wiring.
If fuel pump operation is heard, inspect the filter and lines for restriction.
Start the engine and make sure the pressure decreases about 3-10 psi at idle.
If fuel pressure does not decrease, inspect the fuel pressure regulator and hose.
First disconnect and remove the battery. Then, remove gas cap to release pressure. Than remove fuel lines and drain gas into suitable container. Next, loosen the bolts (you can use a tranny jack or have someone else help hold tank and lower it down. Now you will want to use a BRASS punch. (do NOT use metal or it will cause a spark) Use brass punch and hammer and loosen nut on tank counter-clockwise to loosen sending unit. Once nut is loose, pull out sending unit and unplug the wire harness.
I replaced my water pump on my 92 olds, and the pulley will look slightly different because it's newer, but just make sure its the right one. The pulley does not come off of the water pump, both the water pump and pulley have to be changed. Your new one should come with both the pump and pulley already connected
Have you tested the fuel pressure with a guage? modern cars do not vapor lock, if the fuel pump is working correctly the fuel is constantly be cycled to the fuel rail and back to the tank, a closed loop, if you just get a spurt then the fuel pump is most likely failing, is it noisy, a loud humming when listening at the filler neck with the gas cap off?
I have had the same problem. I changed fuel filter, added fuel injector cleaner, still runs rough as hell at a idle. Didnt think it could be the fuel pump, because ran ok at hiway speeds, it only stalled when giving less gas, not more. So in theory I figured couldn't be fuel pump. I was so wrong. At hiway speeds you have inertia, engine is running faster already etc. Its the fuel pump. 90% of the time in GM cars thats what it is when it behaves this way. to change the fuel pump:
In the tank, the following is a run down of how to replace it..
This is actualy a pretty involved repair. You have to have the car
jacked up on all 4 corners, or up on a car lift. Disconnected battery,
and it is recomended you have as much gas as posible drained from the
tank. Then underneath the car you will find the tank with 2 staps
holding it in place. Those staps should be taken off or at least out of
the way while the tank is being supported. There are vacume lines, the
fuel fill and vent lines, and the wiring harness that all have to be
unhooked. Once you are sure that all lines are disconnected, drop the
tank and pull to the side. Wash the top of the tank off, there will be
dirt and rocks on top of it, and you need to get all of these out of
the way. You will see where the wiring harness goes into the fuel
sending unit. Around that peice is a slide ring that has to be gently
hammered counter clockwise. Once it is free from its retaining clips,
the fuel sending unit will have to be wiggled out very carefully. Once
out, you will see the fuel pump mounted in line on the fuel sending
unit. You will have to work out how its mounted in line, and get it off
and unplugged. Reinstall the new fuel pump and reverse the procedure.
Lock ring O-ring
Posibly the fuel sending unit if you were having problems with your gas gauge.