Voltage at fuel pump

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10-05-2012, 05:33 PM

88cherokeepyles

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Year: 88

Model: Cherokee

Engine: Inline 6 4liter

Voltage at fuel pump

I have 4 V at crank when probing the big wire and the black one at the fuel pump connector harness... What's the verdict? How many volts are there supposed to be? It turns over and starts but then stumbles out - I have 10 psi at the rail.

My fuel pump goes bad often it seems, you'd think if that voltage was too low it wouldn't work when I replace?

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10-05-2012, 05:36 PM

freegdr

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Year: 1989 xj sport 2dr

Model: Cherokee

Engine: 12 hole bosch Injectors

bypass resistor sounds bad it drops voltage down to 10 from 12 i believe .

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10-05-2012, 05:43 PM

88cherokeepyles

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Year: 88

Model: Cherokee

Engine: Inline 6 4liter

Intriguing. So the resistor makes it 10.. thats still a lot more than what I have.

What is interesting to me is that it seems 4 volts is enough to start the thing. Maybe the constant undervoltage kills the pumps eventually?

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