So my 08 Yukon Denali will crank longer after sitting (typically overnight or longer). Not sure reason but assuming loss of fuel pressure or whatever. I also have a string fuel smell when it sits for similar periods, but no gas leak or drips anywhere noticable.
Any ideas where to start with this to diagnose? Hoping issues are related
How much do you mean by "longer", compared to whatever your normal cranking time is?
The common cause of this is a failed check valve in the fuel module. It leaks, causing the system to lose its prime. Turning the key on (not start) for about five seconds, then off for about five more and repeating this two or three times primes the fuel system. After a couple of primes, go straight to start as normal. If it fires right up, then you know you have a leak.
A leaky prime valve doesn't cause a smell of fuel since the leaked fuel just drains out of the lines and back into the tank. So you either have leaky injectors or a leak elsewhere. I'm leaning away from a leaky injector since this usually won't affect cranking times much at all. One or two cylinders having some liquid gas in them won't affect the others from popping off, and all eight cycle multiple times during cranking. So, you'd get more of a rough start that should quickly clear up rather than just an extended start.
My bet is a small leak in a fitting somewhere, like at the bulkhead on top of the tank. Small gasoline leaks can be difficult to pinpoint since the gasoline often evaporates before it's seen. So, sniffing around is your best tool. After you park and it's sitting, sniff around from under the hood to around the top of the tank (through the left rear wheel well should be close) and note where the smell is strongest. You might have to do this a few times as the leaked gas needs time to puddle wherever it is.
