Fuel pump ground wire has power coming from it
#1
Fuel pump ground wire has power coming from it
Hello fellow Jaguar XJS lovers! I have a 94 XJS and it conked out back in May. I have spent the summer tinkering around with it and have put on a host of new sensors, engine components and so one. The most recent was the Crank position sensor. Still won't start. I replaced the fuel pump as well. It doesn't seem to be working so I have the back brace off thinking that MAYBE in my genius I left the fuel pump unplugged. HOWEVER, what I have found in checking for power is that my light comes on in both the power wire and the ground. I know that there should not be power coming from the ground side. The Alldata diagrams show the ground wire as attaching to the body somewhere. Where could this power be coming from???
Thanks,
Tony in NM
Thanks,
Tony in NM
#2
Hello fellow Jaguar XJS lovers! I have a 94 XJS and it conked out back in May. I have spent the summer tinkering around with it and have put on a host of new sensors, engine components and so one. The most recent was the Crank position sensor. Still won't start. I replaced the fuel pump as well. It doesn't seem to be working so I have the back brace off thinking that MAYBE in my genius I left the fuel pump unplugged. HOWEVER, what I have found in checking for power is that my light comes on in both the power wire and the ground. I know that there should not be power coming from the ground side. The Alldata diagrams show the ground wire as attaching to the body somewhere. Where could this power be coming from???
Think of a light switch, current goes to the switch, but not out of it unless the switch is closed, in which case the entire circuit is carrying current.
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warrjon (09-23-2018)
#3
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Greg is correct, of course, in that a ground circuit/ground wire is 'live' because it carries current just like a "+" voltage supply wire...which some call a "hot wire".
If you mean that both wires show "+" voltage then, yes, the pump can't operate.
Just to clarify, are you using an ordinary simple test light with a probe on one side and wire with an alligator clip on the other? If so, with the clip attached to the battery "-" post, the light with glow only if you probe 12 volt "+".
With the alligator clip attached to the battery "+" post, the light will glow only if you probe a ground/earth.
If you had 12 volt "+" on a wire that is attached to a body/chassis ground....you'd have smoke and melted wires
Can you post the diagram you are using and/or describe the test method you are using?
Cheers
DD
If you mean that both wires show "+" voltage then, yes, the pump can't operate.
Just to clarify, are you using an ordinary simple test light with a probe on one side and wire with an alligator clip on the other? If so, with the clip attached to the battery "-" post, the light with glow only if you probe 12 volt "+".
With the alligator clip attached to the battery "+" post, the light will glow only if you probe a ground/earth.
If you had 12 volt "+" on a wire that is attached to a body/chassis ground....you'd have smoke and melted wires
Can you post the diagram you are using and/or describe the test method you are using?
Cheers
DD
#4
Do you have voltage on the ground wire with everything connected or did you disconnect the ground wire, THIS IS IMPORTANT. because if everything was connected then you have a break in the ground connection.
If everything was connected then disconnect the plug from the pump and check continuity to ground, it must be less than 1ohm.
If everything was connected then disconnect the plug from the pump and check continuity to ground, it must be less than 1ohm.
#5
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