Fuel pump has over 300,000 miles.

[Redranger45]

My truck has over 300,000 on the original fuel pump. I’ve been having a cold start misfire issue. Truck starts rough and runs rough for 1 to 2 minutes then smooths out. On occasion it will stutter while accelerating at 60 or 70. But not much. As I continue to troubleshoot this issue I’m wondering if it just makes good sense to replace the fuel pump. I have put a pressure gage on it and it is 57 and seems to hold that at idol but am not able to drive around. It seems to hold at 54 for a good while after cutting off engine.

Could the fuel pump be failing and intermidently causing the rough idol and p0301 and p0303 misfires? Does it make sense to just put in a new one and see if it is the problem?

 

[Dirtman]

In my experience fuel pumps rarely go bad slowly. They just up and die one day. So no, I dont think you should start by just throwing expensive parts like a fuel pump at it without a definitive diagnosis.

What engine?, with 300k miles when was the last major tuneup (plugs, wires etc)? When was the fuel filter last changed? whens the last time you cleaned the MAF, IAC and throttle body? Rule out the simple things first.

 

[Redranger45]

All been done. Rebuilt engine, new injectors, new plugs, wires, IAC, coolant temp sensor, throttle body position sensor.