2007 Yukon Denali Intermittent Crank No Start

[Maxpower_454]

HELP! I have a very nice 07 denali that left me stranded with a crank - no start issue. Did it twice now. It will crank and sputter sometimes but no codes snd good fuel pressure. I replaced yhe fuel pump after the first time it did this. Any ideas? All the posts I see are for no crank no start. Mine will crank, just not start. Fuel pressure tests good. It does it when its idling. Idle will drop, truck shuts off, and won't start. I tried holding the pedal to the floor for flood clear but no luck.

 

[rdezs]

I'm thinking the camshaft position sensor. Often will not throw a code. Do a relearn with a bidirectional scanner after installation. This is one part you want to be ACDelco or genuine GM. Wouldn't hurt to do the crankshaft position sensor also. From experience, it's better to replace one and do a relearn. Then replace the other and repeat the relearn versus replacing them both of the same time.

 

[Maxpower_454]

I'm thinking the camshaft position sensor. Often will not throw a code. Do a relearn with a bidirectional scanner after installation. This is one part you want to be ACDelco or genuine GM. Wouldn't hurt to do the crankshaft position sensor also. From experience, it's better to replace one and do a relearn. Then replace the other and repeat the relearn versus replacing them both of the same time.

I replaced the cam sensor when I bought it a few months ago. it was actually running without one but would crank longer than usual and then start or would not start but then fired right up when the key was turned the second time. replaced with a gm sensor. those are classic cam sensor symptoms, not an intermittent no start. It also gave a cam sensor code before. Not now

 

[j91z28d1]

if you've got fuel pressure at the rail while it'd dying.. next would be to see if the injectors are opening and it's making it into the cyl. pull a plug and check for unburned fuel, or scanner o2 going full lean or rich.

next would be spark. do you have it at the spark plug, if not, do you have power at the coil. if so, do you have the trigger signal from the ecm telling it to fire.

rpm reading in the scanner while cranking no start can help too.

 

[Fless]

Some of the cam and crankshaft sensor issues like long crank times are due to the fact that a CASE relearn isn't done after one or both were changed. If it's not done, the crankshaft position sensor doesn't know where the crankshaft is in relation to the camshaft, so if the ECM doesn't sense a start, it'll try with the opposite relationship. It might take a little time for it to switch, causing the long crank.

The engine can start without a cam signal, or with an unsynchronized signal, but long crank times may be experienced. Eric O describes how it works in this video:

 

[petethepug]

I'm thinking the camshaft position sensor.

I replaced the cam sensor when I bought it a few months ago.

The Ol’ I forgot to mention I replaced the cam sensor when I bought it a few months ago issue.

@rdezs nailed it like he works at the psychic friends network.

 

[donjetman]

@Fless
I like Eric O. I watch his videos for fun and learning all the time.
My favorite saying of his is "IT CAME IN WITH THE MONEY LIGHT ON".

 

[rdezs]

a little off topic, but coming from the psychic Friends Network....Funny how these issues have not changed much since working on that 327 back in 1978. Make sure you have correct valve timing, compression, ignition timing and fuel. Still the basics of any engine. Only now we have sensors that are supposed to tell us which issue it is..... And often this so-called smart system doesn't tell us. And we have somehow stop checking these items ourselves manually. Worse yet, it can be some module buried under the rear passenger seat that prevents the engine starting. And these products are supposed to be better? Or make dealerships more money?

 

[Fless]

@Fless
I like Eric O. I watch his videos for fun and learning all the time.
My favorite saying of his is "IT CAME IN WITH THE MONEY LIGHT ON".

Yeah, I certainly enjoy his sense of humor. "What the world?" If you watch his older videos he's come a long way with his camera presence.

I've learned a lot watching his stuff, as well as Ivan's at Pine Hollow Auto Diagnostics, but some of the issues he diagnoses can be a bit rare and he can get in the weeds. But good info nonetheless.

 

[Maxpower_454]

After about 2 hours of it not starting, it magically starts. It only did it twice. It'll start and run fine now. No long crank, nothing. I can't make it not start so troubleshooting whether it has fuel or spark is tough. If it was that easy I wouldn't be posting here