Okay, I’ve been told I’m nuts by two mechanics. (That’s actually not bad for me since people usually wander up on the street and offer that opinion unsollicited.) Anyway here’s my dilemma.
I have a 2004 Suburban with about 91,000 miles on it. About a month ago it died on the road when the fuel pump failed. I took it to my mechanic and had the pump replaced. My mechanic has been in business for 25 years and generally fixes high-end imports but also does Suburbans because there are so many of them where I live.
Everything with the fuel system is fine since the repair but I have noticed that when I start the car cold there is a much longer “crank time” ( the time between when I turn the key and when the car actually “catches” and starts up.) Before the repair, the car started almost instantly upon turning the key and now it does not and may require more than one “try” to start.
My mechanic has gone over it and said that it’s not the fuel pressure gauge or the ignition switch and has assured me that what I’m hearing is perfectly normal. He was suprised when I told him that before the car would start up immediately even cold and said that was a rarer thing that the problem I’m having now. Does this sound familiar to anyone? As I’ve said, I have a full warranty on the repair and my mechanic has never done me wrong before, so I have no reason not to believe him now.
Here is something to try:
When you’re starting it up, turn the key to the “on” position and leave it there for about 4-5 seconds before starting. Then see if it still takes a while to start. The fuel pump generally runs during that time so this would determine if “priming” would help.
If that’s not the problem, then it’s possible you have a clogged fuel filter or dirty injectors. If the mechanic changed the fuel pump and neglected the filter there could be some “crud” that got stirred up and is clogging things. Also it wouldn’t hurt to buy a bottle of Techron fuel cleaner and dump it in the next time you fill up.
Turning the ignition switch to the run position for 4-5 seconds WILL NOT reprime the fuel system. That’s because when the ignition switch is turned to run position the fuel pump only runs for a second or two and then shuts off.
Instead, turn the ignition switch to the run position for two seconds and then turn the ignition switch off. Repeat this a half dozen times and then try starting the engine. This cycles the fuel pump enough times to reprime the fuel system. If the engine starts right up, there’s a problem with the anti drain-back valve in the new fuel pump that was installed.
Tester
Cycling is a good idea, no need to yell 
The fuel pump has redundant power supplies. The ECM, throough a relay, turns on the pump 2 seconds to prime then off. When the ECM sees an RPM signal it turns the pump on again and it remains on while the engine runs. There is also a switch in the oil pressure sender which closes and powers the pump when engine pressure is above about 20 psi. If the relay fails the engine will start when oil pressure turns on the pump but that usually requires several seconds of cranking.