1989 Ford F-350 no power to fuel pump

Tiny
BHERBIN
  • MEMBER
  • 1989 FORD F-350
  • 7.5L
  • 4WD
  • AUTOMATIC
I have no power going to my fuel pump. A couple weeks ago my truck kept dieing I thought it was the fuel pump so I replaced both the high and low pressure fuel pump but now have no power going to pump. I have checked the eec and fuel pump relay have a constant 12v at yellow wire and 4.5v on red wire. I have checked the inertia switch and its not popped. All my fuses are good. I am about ready to just blow it up. Please help
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Monday, February 16th, 2015 AT 8:24 AM

6 Replies

Tiny
HMAC300
  • EXPERT
Check the brown wire that goes to the inertia switch then see if inertia switch has power on both sides it could be just a bad switch. It could also be a bad relay as well. If no power coming out of brown wire at relay try replacing it with a like relay and see if it works. It can also be a bad ground on fuel pump. I am assuming this h as dual tanks so it could also be the tanks switch I am sending that along on how to check for that.
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Monday, February 16th, 2015 AT 8:45 AM
Tiny
BHERBIN
  • MEMBER
There is only a red and a black wire coming out of the inertia switch
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Monday, February 16th, 2015 AT 8:51 AM
Tiny
HMAC300
  • EXPERT
Unless someone has changed the wiring or it may be old as well. It should be brown on one side and pink on other. Regardless check for power on both sides if power on one but not the other then the inertia is bad or the switch has popped. Or you can use an ohm meter and see if you get 0 through both. The stuff I sent you spells out everything on dual tanks which I am assuming you have as it's 7.5L there are a few thing there that can go wrong like the switch for one on the truck not dash.
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Monday, February 16th, 2015 AT 9:32 AM
Tiny
BHERBIN
  • MEMBER
Let me back up a minute so to begin with my truck ran out of gas I put gas in it and then it started acting funny, it would die then start right back up so I thought it might be a clogged filter so that was the first thing I replaced. That had no affect so I thought the fuel pump might be going out so I changed the high pressure one first. The truck ran fine for a day then when I went to start it the next day nothing so I again changed the high pressure pump thinking I just got a faulty one, but no same problem. OK so I have just swapped out the inertia switch still no results. The truck ism7.5 L 460 motor. The back tank is not hooked up. There is no power to the inertia switch and no power to the pump.
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Monday, February 16th, 2015 AT 10:11 AM
Tiny
HMAC300
  • EXPERT
Check the wire I have pointed out coming from fuel relay at relay. If no power coming out try switching with a like relay to see if it does if it doesn't come out of the relay then the relay may not be turning on so check wires by wiggling to see if anything changes. That means to check previous wires there already tested. If wires come out the brown wire or wire I'm pointing to in pic then there is a broken wire someplace between inertia switch and relay. It could be a connection problem as well so check that due to the age of the truck.
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Monday, February 16th, 2015 AT 12:08 PM
Tiny
HMAC300
  • EXPERT
One other thing check ground going to ecm as it may not be making a good ground and not giving sufficient power to relay
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Monday, February 16th, 2015 AT 12:08 PM

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