Fuelpump will not run and start car part of the time
Replaced fuelpump relay twice same results ,checked voltage at fuelpump with switch on and in start posiion. pump starts car part of the time. no voltage sometimes in the run posiion voltage in the cranking position. bybass relay and pump runs gas into the carb. id it the switch? wiring,or pump?
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Hello, You might try a Relay that controls the PCM or ECU. They would be in the Powerbox where the fuelpump Relay is. Some of the Relays are identical so you could buy 1 and it would be a backup part for several.
You should also look at the other things the Ignition switch turns on in the Run position. Does the radio work, the fan motor, or turn signals? If they do not work look at replacing your Ignition switch.
The PCM and ECU get their power indirectly from the Ignition switch. When all have power they will connect to the fuelpump Relay. Since you said you checked the Relays, I am taking that to mean you checked the fuelpump Relay only. Many times people do not know that there are several relays which all need to connect to get the fuelpump to run. When you determine the Ignition switch is good, then the ECU and PCM relays should be getting power. Have you tested the fuelpressure Regulator? It needs to demand fuel from the pump.
The fuelpump relay depends on the ECU or PCM relays to work. One of the 2 relays may be bad and preventing the fuelpump relay from working. When you get to trouble shooting the terminals you can get wiring diagrams online or the info may be in a book at the Autoparts store.
One of the benefits of using a Dealer with the hardest problems is the tools they have. They have machines with connectors that match every wiring connector inside your car. If one section is unplugged they can test the wire loom section by section until the problem is found.
I hope you have found my solution to be very helpful and that I have brought up a few new areas to try. If trying different parts does not help, you are left with a wire by wire battle to fix this and the Dealers' better tools may make more sense.
Alot of times a bad fuelpump will run with the extra voltage not often but sometimes, i would check the power voltage and ground at the fuelpump, this is the only way to know for sure, if you get 12 volts and have a good ground at the fuelpump then i would say the pump is bad, check all wires going to the battery, make sure there are no loose wires or connections at battery terminals and try changing the fuelpump relay with another one and see if that helps, a bad relay can also cause this, good luck.
when the car won't start. turn ignition switch off . remove gas cap and have someone turn ignition switch on without cranking the engine.listen for a hissing sound that should last for around 3 to 4 seconds, If you don't hear it the most likely problem is the fuel pump. you can further confirm this by checking voltage at the fuel pump by repeating the first step . There should be 12 volt supply for a few seconds when ignition is turned on.If voltage is present and no sound ,replace fuel pump and raplace fuel filter. Fuel pump is in gas tank. this is a very dangerous operation and suggest you bring it to a mechanic.If there is no voltage ,check the electrical plug to fuelpump as to my experience a lot of unsolved intermittent fuel pump problems could be traced to this plug.The other cause could be fuelpump relay or ECU.
The fuelpump is located inside the gas tank, you will need to drop the tank to replace the pump, heres a picture of the pump and in goes in through the top of the tank, the fuelpump is called a fuelpump module because it comes complete with holder sending unit and all other parts as you will see in the picture,hope this helps, good luck.
If you hear the fuelpump operate the first 1 or 2 seconds when the key is turned to RUN position, the fuelpump is working. If you do not hear the fuelpump run, check the Inertia switch which should be in the side panel of the rear cargo area. If you have an owners manual check for the Inertia switch location.
To reset the Inertia switch, hold the button on it for 2-3 seconds. You should now hear the pump run. You may also have a fuelpump relay under the hood in one of the Powerboxes. The Powerbox may have a fusible link from the Battery. When the fusible link is OK and the Pump Relay is OK, there is a fuse in the Fuse panel. Then finally the Ignition switch will trip the Pump relay. As power flows through the wire to the fuelpump the Inertia switch can break the power connection.
So you have 5 powerpoints before the fuelpump will work. Fusible link, Pump Relay, Fuse Panel, Ignition Switch,and Inertia switch. These must all work before the fuelpump can run.
Check in the trunk on the drivers side for an opening in the carpet. There can be 2 switches and 1 is for the Air ride and the other is a fuelpump safety switch. The safety switch is called an "Inertia switch" and it has a push button for Reset. Just hold the button down for 3 seconds and it will reset.
Then turn on the Ignition and you should hear the fuelpump run for a few seconds. It should be ready to start. If the Inertia switch was tripped it is made to kill the fuelpump upon impact. Slamming a door or the trucklid can make it kill the fuelpump.
The fuelpump is primed by the oil pressure switch.When the fuel pressure reaches normal PSI the computer shuts that pressure switch off and turns thepoweron to the fuelpump relay.You have a bad fuel pump relay