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Fuel Pressure problem

7K views 9 replies 4 participants last post by  ron1004 
#1 ·
I have a 99 sportage 5speed 4x4 the fuel pump does not come on when the key is turned to start.but i can jump it on the test plug under the hood,and it comes on but there isnt what i would call a strong stream of fuel.I checked and replaced the fuse(inside)and the relay in the main under the hood what would keep it from activating when the key is turned?
 
#4 ·
Here's a schematic diagram from the web site in my sig.

The power to the fuel pump relay comes from the main relay and as you can see the jumper you used bypass the FP relay and FP fuse.

The ECU controls the FP relay - it should come on when you turn on the IGN switch, but if the CU does not see engine running within about 30 seconds it will take the power off.

Best to trace the power though using the diagram.

Although the fuel pump is capable of a fairly high discharge pressure, it doesn't have such a high flow rate - best to measure the rail pressure.
You could have a plugged main fuel filter or the pump suction strainer - most often the problem lies with the main fuel filter.
 

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#7 ·
Not suggesting flaws in your fault finding, but be aware that the ECU's very rarely fail, so I'd be more inclined to think there's a wiring problem.

I would use a test wire and ground the wire that goes from the FP relay's coil to the ECU starting at the FP relay then down at the ECU's terminal.
 
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