Fuel pump there is no power going to the fuel pump. i jumped the pump with a wire from the battery and the pump works. i have juice at the fuse busbar but i loose the wire in the wire harness.

The only way is to trace the wiring to hunt down that short. Just ck the wiring every few feet until u narrow it down to see where your losing your ignition power. Good luck

The biggest diameter wire goes to biggest fuse. All the wires to the fuse box are the same. Doesn't matter which goes where. The alternator wire goes to the side of the panel. 175 amp fuse.

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The wiring diagrams in the Haynes book should show the washer pump circuit? Often the washer pump shares the same fuse as the wipers.
You could pull off the electrical connector for the washer switch, or the multi-function switch if so equipped, and check for voltage on the pump wire going to the switch, key on. Then check if power going out of switch to the pump-key on and pump switch on. If power on both, the wire from switch to pump must be broken. Run a new wire. If power into switch but none out-switch is bad. If no power into switch for the pump, may have to keep looking for a bad fuse or the wire from fuse panel to the washer switch may have a problem. Hope this helps, good luck.

The main fuel pump in a Volvo is really well built and rarely fails (Bosch simply makes great fuel pumps). A good survival trick if you think a main fuel pump might be bad... give it a quick tap with a wrench. For best results, if possible, tap the pump when cranking the engine (while power is going to the pump). If the pump is bad, often the tap will make it come to life and it may stay running until you shut it off. This trick can get you back on the road and get you home in an emergency. If it's a bad fuel pump relay, this will NOT work as there will be no power going to your pump. If this is the case, you might try the below relay bypass "jump" trick to get power going to the pump. TESTING YOUR FUEL PUMP
How to "JUMP" the fuel pump circuit at your Volvo 240 fuse panel:The fastest method to make the main fuel pump run (bypassing the Fuel Pump Relay) is by jumping two circuits at the fuse panel (left side driver's kick panel).

You can make a jumper from a wire with stripped ends or even a straightened paperclip. Jump the circuits on the right side of the fuses for best results
For a 1979-84 240, jump fuse circuit #5 to #7.
For a 1985-93 240, jump fuse circuit #4 to #6.

If the main fuel pump doesn't begin running when jumped (you should definitely hear it humming), you either have a faulty fuel pump or faulty wiring to the pump (bad wiring is really common under an old 240, near the pump). This test of course assumes your battery is good.
If one of the fuses blows during this test, the pump circuit wiring is shorting to ground somewhere between the fuse panel and the pump.
thx

under the hood in the black main relay and fuse box.look for fuel pump relay.the relays most likely bad. or a loose wire to the fuel pump.has it been wrecked? have to ask yourself alot of questions when you bypass the pump straight to battery and it works. start with simplelest 1st. check main fuse relay and fuse panel 1st.then go to wiring harness that goes to the pump. thank you for choosing fixya.com.

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.

The relay has power on 2 terminals not just one. the relay uses a smaller current to control a larger current...Apply 12 volts to the grey wire aka battery positive and see if the fuel pump will run. if it does ,Check all fuses. and check operation of the fuel ballance module.

i think you answered your own question on if its the pump itself. if you had an extra power source hooked up and it worked then that tells you that is good.. i would try replacing the battery (whether its the problem or not it needs a new one to run anyway.) Think Logically. when you turn that key not only is the fuel pump looking for power. so is the starter the ignition control module. dash lights Daytime running lights if your truck has them and umpteen sensors are begging for power too. someone is the low man on the totem pole and with the fuel pump being the farthest away i would guess thats it.

Electricity is lazy. it takes the shortest path to ground. If it can go through this sensor to get to ground easier than running through the fuel pump then its going to.

one thing that might work (i haven't tried this i just spun this idea off the top of my head) is hook your truck up like your going to jump start it and try to start it and see if that second battery gives it that little extra umph to start.

check mas air flow sensor they used to put power to fuel pump when cranked also check engine computer ,its puts ground to relay when first turned on to give a 2 second shot to the fuel pump to prime fuel system