Help! Must Crank Twice to start!

Rogue909 said:

So my dad just purchased a used 2005 suburban (our last one was an 02 that we ran into the ground) and got a good deal on it...
As with all good deals it has its qwirks, but my dad and I are handy with a wrench (OK not perfect, but on a scale of 1-10 id rate us pretty good at figuring stuff out and getting things fixed) so we figured sure why not, its a suburban, they are tough, the person we bought it from was less then mechanically inclined so its probably something stupid. Besides, we got a deal on it (even if we lose some money on repairs we still end up ahead.)
Ok, dead end now.
Heres what happens... when you crank the truck it cranks strong, but you sit there and crank it and it never fires... until you let go and drop the key back to the run position then crank again. Then it fires like a champ.
First thought was the fuel pump, so we primed it (put key in run and wait....) then cranked, same story.
So we drove it around for a bit (150 miles) hoping to trigger a code pop, nothing.
Took it to a friends dad (a retired mechanic, he has a knack for motors) who told me it must be a sensor issue (his first guess was the crankshaft position sensor), replaced that and no dice. Same story.
Took it to a local shop, had them scan it with one of their super scanners, nothing popped up on the scanners as being irregular.
Gut feeling got the better of me so I picked up a fuel pressure gauge and tried that, now I got some weird numbers....
When you first put the gauge on it reads 0 (car is off).
When the car is switched to run it reads 0. (if im correct it should have pressure here)
When you start cranking the gauge will slowly start going up, if you let it raise all the way to 45-50 it will fire and start running like a champ.
If you stop cranking early (IE when the gauge is at 25~) then drop it to run and crank it again, fires right away.
Once the truck is running, solid 60psi the whole time its running (havnt driven it with gauge on, the gauge we got has a short hose (dumb selection in hindsight) so the hood has to stay open while you ahve the gauge).
When you kill the truck the gauge rapidly drops down to about 9psi (in approx 3 sec)
From there the gauge will slowly drop to 0 (takes about 30-45 sec)
If you attempt to start the truck while the gauge is dropping, it starts fine. If you let it hit 0 psi, start cranking.
It should be noted that once the truck is running it has no problems, instant acceleration (for a suburban anyway), smooth idling, etc. I drove it to class and ran errands yesterday (150 - 200 miles) without any problems.
I checked fuel pump relay, it looked alright, was a little brown on one side, went ahead and replaced it, no dice.
Ran Chevron fuel cleaner through, no change.

Now im confoundled. What would cause those symptoms?
My first thought would be a leaking fuel check valve, but the system depressurizes so fast, and even when its in run it should be priming right?
So then I thought maybe the fuel pump? But then it would show up during drives.
Regulator? The pressure stays a solid 60 once its started.
Line/Fuel Injector? MPG is too high to be "wasting" gas... 17.9 mpg (city65/hwy35)

Maybe its not a fuel issue at all? Friends dad swears its got nothing to do with fuel and its a sensor (I would think the scans would pop something there)

Some specs;
2005 Suburban
Z71
4x4
5.3
FlexFuel
110k miles

Anyone have any thoughts? Im desperate here >.<

Click to expand...

Rogue909 said:

So my dad just purchased a used 2005 suburban (our last one was an 02 that we ran into the ground) and got a good deal on it...
As with all good deals it has its qwirks, but my dad and I are handy with a wrench (OK not perfect, but on a scale of 1-10 id rate us pretty good at figuring stuff out and getting things fixed) so we figured sure why not, its a suburban, they are tough, the person we bought it from was less then mechanically inclined so its probably something stupid. Besides, we got a deal on it (even if we lose some money on repairs we still end up ahead.)
Ok, dead end now.
Heres what happens... when you crank the truck it cranks strong, but you sit there and crank it and it never fires... until you let go and drop the key back to the run position then crank again. Then it fires like a champ.
First thought was the fuel pump, so we primed it (put key in run and wait....) then cranked, same story.
So we drove it around for a bit (150 miles) hoping to trigger a code pop, nothing.
Took it to a friends dad (a retired mechanic, he has a knack for motors) who told me it must be a sensor issue (his first guess was the crankshaft position sensor), replaced that and no dice. Same story.
Took it to a local shop, had them scan it with one of their super scanners, nothing popped up on the scanners as being irregular.
Gut feeling got the better of me so I picked up a fuel pressure gauge and tried that, now I got some weird numbers....
When you first put the gauge on it reads 0 (car is off).
When the car is switched to run it reads 0. (if im correct it should have pressure here)
When you start cranking the gauge will slowly start going up, if you let it raise all the way to 45-50 it will fire and start running like a champ.
If you stop cranking early (IE when the gauge is at 25~) then drop it to run and crank it again, fires right away.
Once the truck is running, solid 60psi the whole time its running (havnt driven it with gauge on, the gauge we got has a short hose (dumb selection in hindsight) so the hood has to stay open while you ahve the gauge).
When you kill the truck the gauge rapidly drops down to about 9psi (in approx 3 sec)
From there the gauge will slowly drop to 0 (takes about 30-45 sec)
If you attempt to start the truck while the gauge is dropping, it starts fine. If you let it hit 0 psi, start cranking.
It should be noted that once the truck is running it has no problems, instant acceleration (for a suburban anyway), smooth idling, etc. I drove it to class and ran errands yesterday (150 - 200 miles) without any problems.
I checked fuel pump relay, it looked alright, was a little brown on one side, went ahead and replaced it, no dice.
Ran Chevron fuel cleaner through, no change.

Now im confoundled. What would cause those symptoms?
My first thought would be a leaking fuel check valve, but the system depressurizes so fast, and even when its in run it should be priming right?
So then I thought maybe the fuel pump? But then it would show up during drives.
Regulator? The pressure stays a solid 60 once its started.
Line/Fuel Injector? MPG is too high to be "wasting" gas... 17.9 mpg (city65/hwy35)

Maybe its not a fuel issue at all? Friends dad swears its got nothing to do with fuel and its a sensor (I would think the scans would pop something there)

Some specs;
2005 Suburban
Z71
4x4
5.3
FlexFuel
110k miles

Anyone have any thoughts? Im desperate here >.<

Click to expand...

Rogue909 said:

So my dad just purchased a used 2005 suburban (our last one was an 02 that we ran into the ground) and got a good deal on it...
As with all good deals it has its qwirks, but my dad and I are handy with a wrench (OK not perfect, but on a scale of 1-10 id rate us pretty good at figuring stuff out and getting things fixed) so we figured sure why not, its a suburban, they are tough, the person we bought it from was less then mechanically inclined so its probably something stupid. Besides, we got a deal on it (even if we lose some money on repairs we still end up ahead.)
Ok, dead end now.
Heres what happens... when you crank the truck it cranks strong, but you sit there and crank it and it never fires... until you let go and drop the key back to the run position then crank again. Then it fires like a champ.
First thought was the fuel pump, so we primed it (put key in run and wait....) then cranked, same story.
So we drove it around for a bit (150 miles) hoping to trigger a code pop, nothing.
Took it to a friends dad (a retired mechanic, he has a knack for motors) who told me it must be a sensor issue (his first guess was the crankshaft position sensor), replaced that and no dice. Same story.
Took it to a local shop, had them scan it with one of their super scanners, nothing popped up on the scanners as being irregular.
Gut feeling got the better of me so I picked up a fuel pressure gauge and tried that, now I got some weird numbers....
When you first put the gauge on it reads 0 (car is off).
When the car is switched to run it reads 0. (if im correct it should have pressure here)
When you start cranking the gauge will slowly start going up, if you let it raise all the way to 45-50 it will fire and start running like a champ.
If you stop cranking early (IE when the gauge is at 25~) then drop it to run and crank it again, fires right away.
Once the truck is running, solid 60psi the whole time its running (havnt driven it with gauge on, the gauge we got has a short hose (dumb selection in hindsight) so the hood has to stay open while you ahve the gauge).
When you kill the truck the gauge rapidly drops down to about 9psi (in approx 3 sec)
From there the gauge will slowly drop to 0 (takes about 30-45 sec)
If you attempt to start the truck while the gauge is dropping, it starts fine. If you let it hit 0 psi, start cranking.
It should be noted that once the truck is running it has no problems, instant acceleration (for a suburban anyway), smooth idling, etc. I drove it to class and ran errands yesterday (150 - 200 miles) without any problems.
I checked fuel pump relay, it looked alright, was a little brown on one side, went ahead and replaced it, no dice.
Ran Chevron fuel cleaner through, no change.

Now im confoundled. What would cause those symptoms?
My first thought would be a leaking fuel check valve, but the system depressurizes so fast, and even when its in run it should be priming right?
So then I thought maybe the fuel pump? But then it would show up during drives.
Regulator? The pressure stays a solid 60 once its started.
Line/Fuel Injector? MPG is too high to be "wasting" gas... 17.9 mpg (city65/hwy35)

Maybe its not a fuel issue at all? Friends dad swears its got nothing to do with fuel and its a sensor (I would think the scans would pop something there)

Some specs;
2005 Suburban
Z71
4x4
5.3
FlexFuel
110k miles

Anyone have any thoughts? Im desperate here >.<

Click to expand...

RayVoy said:

Let it sit over night, then in the morning spray a little gas or starter fluid into the throttle body, see if it starts any faster.
It it does, it's a fuel delivery problem
If there is no difference, it's probably a spark problem.

Let us know what happens.

Click to expand...

Kanode said:

Any of you guys ever figure this out? I also have to turn my key twice about 2/3's of the time I try to start my truck. 2000 Silverado 5.3L. The problem started when I replaced the camshaft position sensor about a year ago. I replaced the camshaft position sensor because the truck wouldn't start at all. After I replaced it the truck started right up, but then the next time I had to crank twice and it's been this way ever since. My fuel pressure is normal. When I pulled the old camshaft position sensor out it was coated with sludge, so possibly there is more sludge on the new one. I've had regular oil changes and have run an engine flush through it before the last 2 oil changes.

Click to expand...