Impala 2005, 3.4. A week ago car would not start as normal. Turn key and would try to turn over, but wouldn’t start. On fifth try I gave it some gas and car started. On initial take off in mornings car seems to be a little sluggish for the first few miles then smooths out. This past week I have put in fuel injector cleaner and have changed the fuel filter. Old filter was VERY dirty. Car is cranking but there is a pop right before it fires up. I got the fuel pressure checked and it registered at 50psi. I was told that it should register at least 80psi and it was suggested that I replace the fuel pump. I have also been told that when a fuel pump goes it just goes, that it is not a gradual thing. Is this a fuel pump problem or should I do some further research to find out what the popping sound is now when it cranks or is the psi indicitive of a fuel pump going bad?
Did anyone test the coldstart injection? Most cars today check the air temp and adjust the fuel to the coolant temp. As the engine warms the cold start sequence turns down the fuel volume to a lean mix. Temp sensors can cause this problem. The fuel pressure should be in the 60 psi range but 50 is probably fine. The mix does not depend on the fuel pressure but the oxygen sensor. Your starting problems if due to the temp could be fixed with a $30 sensor and removing the battery cable for 15 min or so. That will tell the comp to start with the right mix and retrim the long fuel mix.
If your fuel pressure is 50psi and it is supposed to be 80psi then I would be looking at replacing the fuel pump. Driving around with that dirty fuel filter didn’t help the pump at all.
I would not discount the cold start mix issue noted by euryale and would check the coolant temp sensor. But if you have a fuel injection system built needed 80psi, then 50psi will make a mess.