How much voltage to fuel pump?

97fordrunner · 11-07-2009, 05:48 PM

I got a '89 BII the fuel pump in tank wasn't working due to some moron cutting just about every wire about three times and twisting them together so with that all fixed I am getting about 6 volts to the pump and no workie. With a 12 volt jumper the pump works and pumps. Is it supposed to be 6 or 12 volts and has anyone had an issue with this before?

**Earl43P** · 11-07-2009, 06:17 PM

Definitely 12v.

97fordrunner · 11-07-2009, 06:48 PM

any ideas why I would only be getting half that thru the Fuel Circuit?

03ranger4x4 · 11-07-2009, 07:39 PM

i have a few ideas, you could always check it out.

Are you sure your only getting 6v AT the pump ONLY? Stupid question, but its best to start with the simplest cuases 1st before going more in depth. Check the battery terminal JUST to be sure. even if the truck cranks over fine. you never know.

another thing, are you checking voltage at the pump while its connected, or at the connector while the pump is not connected. If you are taking it with the pump connected, theres a chance that the voltage is fine, and the pump is siezed up. If thats the case, the pump would be drawing maximum amperage, and given the size of the wire, or the amount the relay or fuse is able to carry, it could technically drop the voltage of the fuel pump circuit that low, possibly even without blowing a fuse.

then theres another thing, check the relay connections, and scan the wire (to the best you can, i know it can be tricky) all the way to the pump, and check for any shorts to ground or any partialy opens in the wire. The relay may also be bad, cuasing only a little voltage to slip by, but ive never seen this happen. Its unlikley, since its typically a part that fails complelety when it does go out. but it can happen, and given your readings, i would check it out to be sure.

I would suggest after proving that the fuel pump itself isnt bad, is to disconnect the battery and disconnect the pump connector, and take ohm readings from the fuel pump postive wire to ground at all the pionts you can running working towards to the pump to see if it is shorting to ground anywhere, even if you get a partial reading, that is bad. You should see infinate ohms (open) all the way to the pump.

Good luck, this problem is rather simple,and after taking the checks i menchined,you should narrow down the cuase in no time

97fordrunner · 11-07-2009, 08:00 PM

I was checking it at the connector with it unhooked from the pump. The pump operates ok with a jumper. I will check the relay for sure. I replaced a ton of wire that had opens and twisted wires it was a terrible mess really. Thanks for the info I'll look at all that tomorrow

97fordrunner · 11-08-2009, 06:43 PM

Got it running, Like a Top for that matter, found a bad wire and also a twisted fuel line

11-07-2009, 05:48 PM	#1
97fordrunner Member Join Date: Aug 2007 Location: New Richmond, WI Year: 1997 Make: Ford Model: Ranger Engine: 4.0 Class: 4x4 Used For: Weekend Wheeler Posts: 821 Rep Power: 13 iTrader: (6)	How much voltage to fuel pump? I got a '89 BII the fuel pump in tank wasn't working due to some moron cutting just about every wire about three times and twisting them together so with that all fixed I am getting about 6 volts to the pump and no workie. With a 12 volt jumper the pump works and pumps. Is it supposed to be 6 or 12 volts and has anyone had an issue with this before? __________________ '97 Ranger 4.0, Auto 5" custom Suspension 3" Body lift. 35" Baja Claws, 4.88 gears Rear locked. Warn jeep Hubs. Build Thread "since we didn't know what to do, we sat down and did nothing" - James May, Top Gear BBC Ranger Militia Member
	Tweet

11-07-2009, 06:17 PM	#2
Earl43P Premium Member Join Date: Aug 2007 Location: E-City, NC Year: 2000 Make: Ford Model: Ranger Engine: 3.0 Class: 4WD Used For: DD Posts: 2,784 Rep Power: 21 iTrader: (1)	Definitely 12v.
	Tweet

11-07-2009, 06:48 PM	#3
97fordrunner Member Join Date: Aug 2007 Location: New Richmond, WI Year: 1997 Make: Ford Model: Ranger Engine: 4.0 Class: 4x4 Used For: Weekend Wheeler Posts: 821 Rep Power: 13 iTrader: (6)	any ideas why I would only be getting half that thru the Fuel Circuit? __________________ '97 Ranger 4.0, Auto 5" custom Suspension 3" Body lift. 35" Baja Claws, 4.88 gears Rear locked. Warn jeep Hubs. Build Thread "since we didn't know what to do, we sat down and did nothing" - James May, Top Gear BBC Ranger Militia Member
	Tweet

11-07-2009, 07:39 PM	#4
03ranger4x4 Member Join Date: Oct 2009 Year: 2003 Make: Ford Model: Ranger Posts: 183 Rep Power: 8 iTrader: (0)	i have a few ideas, you could always check it out. Are you sure your only getting 6v AT the pump ONLY? Stupid question, but its best to start with the simplest cuases 1st before going more in depth. Check the battery terminal JUST to be sure. even if the truck cranks over fine. you never know. another thing, are you checking voltage at the pump while its connected, or at the connector while the pump is not connected. If you are taking it with the pump connected, theres a chance that the voltage is fine, and the pump is siezed up. If thats the case, the pump would be drawing maximum amperage, and given the size of the wire, or the amount the relay or fuse is able to carry, it could technically drop the voltage of the fuel pump circuit that low, possibly even without blowing a fuse. then theres another thing, check the relay connections, and scan the wire (to the best you can, i know it can be tricky) all the way to the pump, and check for any shorts to ground or any partialy opens in the wire. The relay may also be bad, cuasing only a little voltage to slip by, but ive never seen this happen. Its unlikley, since its typically a part that fails complelety when it does go out. but it can happen, and given your readings, i would check it out to be sure. I would suggest after proving that the fuel pump itself isnt bad, is to disconnect the battery and disconnect the pump connector, and take ohm readings from the fuel pump postive wire to ground at all the pionts you can running working towards to the pump to see if it is shorting to ground anywhere, even if you get a partial reading, that is bad. You should see infinate ohms (open) all the way to the pump. Good luck, this problem is rather simple,and after taking the checks i menchined,you should narrow down the cuase in no time
	Tweet

11-07-2009, 08:00 PM	#5
97fordrunner Member Join Date: Aug 2007 Location: New Richmond, WI Year: 1997 Make: Ford Model: Ranger Engine: 4.0 Class: 4x4 Used For: Weekend Wheeler Posts: 821 Rep Power: 13 iTrader: (6)	I was checking it at the connector with it unhooked from the pump. The pump operates ok with a jumper. I will check the relay for sure. I replaced a ton of wire that had opens and twisted wires it was a terrible mess really. Thanks for the info I'll look at all that tomorrow __________________ '97 Ranger 4.0, Auto 5" custom Suspension 3" Body lift. 35" Baja Claws, 4.88 gears Rear locked. Warn jeep Hubs. Build Thread "since we didn't know what to do, we sat down and did nothing" - James May, Top Gear BBC Ranger Militia Member
	Tweet

11-08-2009, 06:43 PM	#6
97fordrunner Member Join Date: Aug 2007 Location: New Richmond, WI Year: 1997 Make: Ford Model: Ranger Engine: 4.0 Class: 4x4 Used For: Weekend Wheeler Posts: 821 Rep Power: 13 iTrader: (6)	Got it running, Like a Top for that matter, found a bad wire and also a twisted fuel line __________________ '97 Ranger 4.0, Auto 5" custom Suspension 3" Body lift. 35" Baja Claws, 4.88 gears Rear locked. Warn jeep Hubs. Build Thread "since we didn't know what to do, we sat down and did nothing" - James May, Top Gear BBC Ranger Militia Member
	Tweet

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode