[shorod]

There are numerous issues that could cause this type of slow start. You could have a leaking injector as you mention, but this would usually only cause an issue after sitting more than 15 minutes and less than 4 hours or so. Beyond that time, the leak would bleed off any pressure in the fuel rail and allow it to leak past the rings into the crankcase.

You could have low system voltage as you mention, have you checked the system voltage with a meter during the start attempt? What is the voltage?

You could also have low fuel pressure due to a weak fuel pump, faulty fuel pressure regulator, or abnormal fuel system restriction (such as a plugged fuel filter). Have you checked the fuel pressure at the fuel rail?

Bad spark plugs could lead to difficulty starting. How many miles are on the car, and have the plugs ever been changed?

An abnormal restriction in the exhaust could cause symptoms such as you describe, but are not very common.

You could have a vacuum leak as well, but that would often lead to a rough idle once the car does start.

An EGR valve that is stuck open could cause difficulty starting, but again you would most likely notice a rough idle once the car did start.

What condition is the air filter in? If it is restricted, it could cause issues.

Immediately after the car starts, what does the exhaust look/smell like? Is it dark and smell like there is a high concentration of raw fuel in it?

-Rod