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Discussion Starter · #1 ·
I just installed a new electric fuel pump in the tank of a 1996 Jeep Grande Cherokee Laredo with a 4.0 ltr. inline 6. I am not sure of the pump is working or the wiring is bad. there are four wires in the pump housing unit. Two for the sending unit ( Black and Blue) a red one and light orange one for the electric pump itself. I did not mark which was positive or negative. I am not getting any power indication on any of the external 4 prong connector plugs outside of the tank. Problems with the connectors ? The fuel sending unit is working properly according to the dash gauge and how much fuel is in the tank. The pump was bought at O'Reillys by the customer along with a new sock (which was wrong) and fuel filter. The fuel relay is the same for the starter and I have swapped them back and forth and the starter still works so I am sure it's not that. The Jeep has a New battery fully charged and running the Engine on the "wanna be starting fluid" it shows 13.8 volts on my tester. Has anyone else had this problem with the Jeeps before and which wire is the hot wire on the fuel pump ? Orange or red? Will it ruin the electric fuel pump if I put 12 volts to one and ground the othe or just make the pump spin backwards ? The Pump is a Master Pro. Has anyone had a bad brand new one before ?? I can pull the tank again without too much trouble but would hate to do so if there were another option/ sugestions !!! Thanks JYT ***
 

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You're going to need a helper. The ASD relay will provide power to the pump for a couple seconds when turning the key to run . It then shuts off and waits for a rpm signal from the engine.

You need to be checking for power while someone turns the key.

You might actually be missing a crank sensor signal to the computer.
 

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first things first , did you by pass the F/P relay and check for power at the F/P connector
 

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There should be 5 wires at your pump connector.

a dark green/red, this is the power feed that comes from the pump relay.

a black/light blue wire. This is the sensor ground wire for the level sending unit. This comes from the engine controller.

a dark blue wire. This is the sending unit's output to the instrument cluster for the gauge.

a dark blue/white wire. This goes to the cluster for the low fuel message.

a black wire. This is the ground for the pump motor.

your F/P connector should be like the one below , you only want #1 and #6

Motor vehicle Automotive lighting Rectangle Font Automotive exterior
 

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Discussion Starter · #5 ·
first things first , did you by pass the F/P relay and check for power at the F/P connector
No I did not ! Just checked for power at connector with the key on but not cranking the engine over. Will do that. There are only four wires going to this pump. This does help tho. Thanks JYT ***
 

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Discussion Starter · #6 ·
You're going to need a helper. The ASD relay will provide power to the pump for a couple seconds when turning the key to run . It then shuts off and waits for a rpm signal from the engine.

You need to be checking for power while someone turns the key.

You might actually be missing a crank sensor signal to the computer.
Thanks RR this also helps. JYT ***
 

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Discussion Starter · #7 ·
Got it fixed Guys !!! The Power wire at the plug was not getting power thru it so I made a jumper wire with spade clips for future removal if necessary. Thanks for all the great input ! JYT ***
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you soldered those connections right , other wise l would have just CUT the wires and used the low temp solder heat shrink butt connectors
 
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