Q: Truck won't start unless I remove the fuel pump relay

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I just did a head job on my 90 nissan d21 with a 2.4 now the truck won't start unless you unhook the fuel pump relay then as soon as it cranks hurry and hook it back up. When it does crank it runs really rough and idle up and down. Once you shut it off you have to go through the whole process over again. I've changed the fuel pressure regulator and still no change.

My car has 165000 miles.
My car has a manual transmission.

Hey there. This is a sign of a failing fuel pump or potentially a faulty power connection to the fuel pump. As you know, if the fuel pump fails to supply adequate fuel pressure to the motor, this will cause an imbalanced fuel load to be supplied to the motor resulting in the erratic idle you have experienced. I would recommend replacing the fuel pump.

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