Long crank after sitting?

[Denali2k8]

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

 

[RED TAHOE LS]

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

Inline fuel filter, it's underneath on the frame rail, inexpensive.

 

[avalonandl]

How many miles. The pump can lose prime. Usually after that your on borrowed time...

 

[Fless]

Test the fuel pressure using the correct procedure, KOEO (key on, engine off). Post up the initial value.

After turning off the key, document the time it takes for the pressure to leak down, and what the pressure is at, say, 5 min. intervals after key off. Based simply on the strong fuel smell I'd guess a leaky injector. If it does leak down, there is a pressure leakdown valve in the fuel pump as @avalonandl noted, so there could be other causes. Doesn't this truck have an FPCM?

When it cranks long, floor the gas pedal and that puts it into clear flood mode. If it fires right up the fuel is likely leaking into a cylinder or two after shutdown.

 

[OR VietVet]

Last time I read here about this type of problem and the smell with it, was some hoses on top of tank but like @Fless said, bet it is leaking down and could very well be an injector. Don't put this off because could be dangerous if external fuel leak. Also, if is an injector leaking down, the gas gets in to the oil and breaks the oil down and can damage the engine. Get that fuel pressure gauge on there and do the listed tests. Also, there is no external fuel filter, is all at the pump in the tank.

 

[iamdub]

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.

 

[Denali2k8]

The smell is def strongest back by the tank

 

[OR VietVet]

I still think, like I had said, the leak is back by the tank and hoses and the pressure that is supposed to hold after shut down is bleeding off at that leak. Only one way to find out. Crawl under there with a light and mirror and start up the rig and see if you can see the leak. Hell, maybe it will be obvious and blow fuel right in the air and hopefully not in your face.

 

[iamdub]

The smell is def strongest back by the tank

Considering how well-sealed the fuel and vapor system is supposed to be on these things, you most definitely have a leak. You shouldn't be able to smell any fuel at all.

There's only one visible junction in the system in that area that is part of the pressure side of it. It's in front of the tank, near the frame rail. If it's not leaking from there, then it's likely on top of the tank.

Dropping the tank isn't the easiest task, so you might wanna consider replacing the pump module when you drop it to repair the leak. If the leak is a cracked and/or corroded fitting on the bulkhead, then you'd be replacing the module anyway.

 

[wsteele]

Inline fuel filter, it's underneath on the frame rail, inexpensive.

I don't think this model year has an inline fuel filter along the frame rail. I think the fuel filter is in the tank with the pump assembly. In any case, it isn't the filter.

 

[wsteele]

Test the fuel pressure using the correct procedure, KOEO (key on, engine off). Post up the initial value.

After turning off the key, document the time it takes for the pressure to leak down, and what the pressure is at, say, 5 min. intervals after key off. Based simply on the strong fuel smell I'd guess a leaky injector. If it does leak down, there is a pressure leakdown valve in the fuel pump as @avalonandl noted, so there could be other causes. Doesn't this truck have an FPCM?

When it cranks long, floor the gas pedal and that puts it into clear flood mode. If it fires right up the fuel is likely leaking into a cylinder or two after shutdown.

I agree, and yes it does have a FPCM.

 

[Fless]

Considering how well-sealed the fuel and vapor system is supposed to be on these things, you most definitely have a leak. You shouldn't be able to smell any fuel at all.

There's only one visible junction in the system in that area that is part of the pressure side of it. It's in front of the tank, near the frame rail. If it's not leaking from there, then it's likely on top of the tank.

Dropping the tank isn't the easiest task, so you might wanna consider replacing the pump module when you drop it to repair the leak. If the leak is a cracked and/or corroded fitting on the bulkhead, then you'd be replacing the module anyway.

Not part of the pressure system but if the fuel pump module gasket is leaking you can get fumes from that, too. Just dealt with that on my '04 due to a failing evap test; when performing a purge and seal, the seal wouldn't hold. Like @iamdub mentioned, if you get to the point of having to drop the tank it may be a good idea to have a whole new pump module ready just in case.

 

[okfoz]

I was wondering if there was an update to this? If so what was the problem?