Fuel pump keeps going out

Tiny
JUSTIN66106
  • MEMBER
  • 1995 CHEVROLET BLAZER
  • 4.3L
  • V6
  • 4WD
  • AUTOMATIC
  • 270,000 MILES
When I pull it out of tank half the wires and plug is melted. It is only getting 8.5 volts. What can make this happen all of a sudden?
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Saturday, April 13th, 2019 AT 5:53 PM

12 Replies

Tiny
SCGRANTURISMO
  • EXPERT
Hello,

Check the ground to the fuel pump and also check the amperage of the fuse to the fuel pump circuit. If the ground to the fuel pump has a lot of excessive resistance to it will not allow the current to return to the battery, heating the wires up to the point of melting them. The fuse protecting this circuit might be too high of an amperage fuse and not blowing like it should. Think of electricity like water, they flow and work very similarly. If you had water in a pool (battery) and it was flowing to a water wheel to turn it (fuel pump) through a pipe(wire) and the return pipe(ground/vehicle body to battery -) was blocked not allowing the water to return to the pond, but the water kept coming from the pond, do you think that return pipe would be under pressure? Would the water wheel eventually stop turning? I have included wiring diagrams for the fuel pump in the diagrams down below with the part of the fuel pump circuit we are concerned with high lighted.
Please check this out and get back to us with what you are able to find out please.

Thanks,
Alex
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Saturday, April 13th, 2019 AT 6:28 PM
Tiny
JUSTIN66106
  • MEMBER
We tested the voltage from the ground from the battery to the plug for the fuel pump and only got 8.6 volts.
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Saturday, April 13th, 2019 AT 8:48 PM
Tiny
SCGRANTURISMO
  • EXPERT
Hello again,

What pin on the connector dis you test? The positive (gray) wire or the negative (black) wire? And was the vehicle running or not?

Thanks,
Alex
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Saturday, April 13th, 2019 AT 9:46 PM
Tiny
JUSTIN66106
  • MEMBER
I tested the gray. The vehicle was on.
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Saturday, April 13th, 2019 AT 9:52 PM
Tiny
SCGRANTURISMO
  • EXPERT
Hello again,

Okay, with the van running can you test the black from the connector to the ground where it connects to the body. Test in VDC, please, as before and get back to us with that reading to please. This is what is known as a voltage drop test and it will tell us if there excessive resistance in the ground wire.

Thanks,
Alex
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Saturday, April 13th, 2019 AT 11:02 PM
Tiny
JUSTIN66106
  • MEMBER
I did yesterday and I believe it was negative 3.21.
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Sunday, April 14th, 2019 AT 8:25 AM
Tiny
SCGRANTURISMO
  • EXPERT
Hello again,

Okay, there's your problem. The ground wire or the ground connection to the frame is bad. You should have no more than 0.1 volts in any segment of the circuit. The goal of any circuit is to dump all available voltage across the load, which in this circuit is the fuel pump, but because of corrosion, broken wire, bad connector, you are dumping 3.21 volts across the ground wire because of the resistance in this segment of the circuit. Replace the connector a new one and run a new ground wire and make sure the connection to the frame is clean, tight, and metal to metal and you should be back on the road worry free.

Thanks,
Alex
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Sunday, April 14th, 2019 AT 8:59 AM
Tiny
JUSTIN66106
  • MEMBER
Well, I do not know what I did yesterday but I am not getting any negative volts from the negative today.
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Sunday, April 14th, 2019 AT 10:05 AM
Tiny
JUSTIN66106
  • MEMBER
I went ahead and pulled the pump and there is no visible damage. Still only getting 8.6 volts.
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Sunday, April 14th, 2019 AT 11:11 AM
Tiny
SCGRANTURISMO
  • EXPERT
Hello again,

You got negative volts yesterday because you had the positive and negative terminals on the multi-meter switched around, but that makes no difference. You have them one way and it's negative, the other way it's positive. That's not what is important, what's important is the voltage number itself. The fuel pump is not the issue. It is the ground wire from the fuel pump and the ground point where is grounds to the vehicle body. There is a massive amount of unwanted resistance in this wire and connection to the body frame, and this is your problem. Again, get a new wire harness connector with pigtails and install. Make sure the screw you use to ground the ground wire makes clean, tight, metal to metal connection with the frame and you are done.

Thanks,
Alex
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Sunday, April 14th, 2019 AT 6:15 PM
Tiny
JUSTIN66106
  • MEMBER
I did and its still only 8.5.
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Sunday, April 14th, 2019 AT 6:20 PM
Tiny
SCGRANTURISMO
  • EXPERT
Hello again,

Okay, I was just checking to make sure you understand what is going on. What we had you do is called a voltage drop test. It showed that voltage was present in the ground wire. The voltage from the ground wire to the ground connection should read 0.1V. This indicated 100% that the wire and/or ground connection is bad and needs to be replaced. Once this is done, your fuel pump will run as it was designed to.

Thanks,
Alex
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Wednesday, April 17th, 2019 AT 10:30 PM

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