No start, then start

[AndyMac]

I had a 07 c6 that was doing this. Classic signs of something funky in the cam sensor/ pick up.

Pulled the timing cover and bolts were backing out of the cam.

Had the exact same problem on my 05 C6, random start/no start. A few weeks later it started knocking and threw P0341 IIRC. Cam bolts coming out and wheel was contacting sensor. It was a bone stock car at the time.

Good luck!

[AndyMac]

Also, I hooked up my Snap-On Solus pro scan tool and watched cam and crank counts. The cam count wouldn't change until I reved the car to about 1500rpm.

[5_Liter_Eater]

The thing is, when it's cranking and not starting I can see the cam sensor counts incrementing. A while back I also measured the distance from the gear to the cover at different points of rotation thinking that the Summit gear was not to spec, and it checked out.

Thanks for the additional input/experience though.

[carlrx7]

I finally got a chance to get under the car, forgot to connect the sensor :derp:

just got done filling the trans, fuk GM for making it so retarded to fill an A6 on a vette.

-Carl

[5_Liter_Eater]

OK, haven't messed with this in a while. I just scanned it when it's cranking without starting and I am getting an RPM signal so it's not the crank sensor. Soooooo?

[Wrenched]

I'd be looking at cam & crank on a labscope. Do you have any access to one? Cam, Crank correlation could be the issue. I've seen this problem with no codes too.

[5_Liter_Eater]

You mean like an o-scope? I suppose I could wrangle one up somewhere. What would I be looking for exactly?

[DrLoch]

You'd be looking for the pulse train coming or lack of from the sensors.

[ls1x2]

[5_Liter_Eater]

So since the motor is apart I was able to get a good look at the internals. The cam gear was intact and the reluctor looks straight as an arrow. Could it be that the reluctor is clocked wrong? Ignortant question perhaps, I'm not sure if it even matters the orientation of the reluctor in relation to the crank.

[carlrx7]

So since the motor is apart I was able to get a good look at the internals. The cam gear was intact and the reluctor looks straight as an arrow. Could it be that the reluctor is clocked wrong? Ignortant question perhaps, I'm not sure if it even matters the orientation of the reluctor in relation to the crank.

Blame the Tuner or the Engine Builder, one of them fucked up somewhere! lol

[5_Liter_Eater]

Caaaaaaarrrrrlllllll!

[ElecTech]

So since the motor is apart I was able to get a good look at the internals. The cam gear was intact and the reluctor looks straight as an arrow. Could it be that the reluctor is clocked wrong? Ignortant question perhaps, I'm not sure if it even matters the orientation of the reluctor in relation to the crank.

Are you running an aftermarket cam gear?

[5_Liter_Eater]

Yes, it's a double roller from Summit. I do run an iron block so I guess I could take that out of the equation and run the rear cam sensor....or can I? I'd really like to not have this problem when the new motor goes in.

[ElecTech]

Yes, it's a double roller from Summit. I do run an iron block so I guess I could take that out of the equation and run the rear cam sensor....or can I? I'd really like to not have this problem when the new motor goes in.

The reason I asked is I have had similar problems on a couple of cars over the years and something we discoverd the other day made me think about situations like this.

The issue was with a transmission output speed sensor. We kept loosing a speed signal and after all attempts at wiring fixes, it was suggested that it maybe the speed sensor is TOO close. Seemed far fetched, but tried shimming it and damn if it didn't work. The best I could figure is that the sensor being that close is still reading the grooves and never really makes a transition from high to low.

It makes me wonder if the same could be true on the cam sensor. Especially when dealing with a double roller cam gear or one that may have a shallow groove cut. Both cars I've had with this issue were also intermitten but both had double roller LS2 style set-ups and one I know for sure didn't have the issue until after the cam and chain install.

Just something to think about.

[5_Liter_Eater]

Good points. Something I may have neglected to mention is that when I first dropped the motor in it was throwing cam sensor codes which ended up being a frayed wire but before I found that I thought it was the cam gear so I took measurements of the cam sensor, cover and gear and filed the cam sensor boss (~.010" IIRC) to get it closer to the gear. The thing is the cam sensor count increments while the car is cranking and doesn't start which makes me think it's fine but it could be a combination of the sensor being too close and the orientation of the cam gear on initial start.

The reason I asked is I have had similar problems on a couple of cars over the years and something we discoverd the other day made me think about situations like this.

The issue was with a transmission output speed sensor. We kept loosing a speed signal and after all attempts at wiring fixes, it was suggested that it maybe the speed sensor is TOO close. Seemed far fetched, but tried shimming it and damn if it didn't work. The best I could figure is that the sensor being that close is still reading the grooves and never really makes a transition from high to low.

It makes me wonder if the same could be true on the cam sensor. Especially when dealing with a double roller cam gear or one that may have a shallow groove cut. Both cars I've had with this issue were also intermitten but both had double roller LS2 style set-ups and one I know for sure didn't have the issue until after the cam and chain install.

Just something to think about.

[DSteck]

Have you hooked up noid lights to the spark and injectors to see what they're doing when it doesn't start?

[5_Liter_Eater]

Never investigated the injectors but I took a plug wire off and hooked up a plug and grounded it and it was throwing spark while cranking with no start.

And it smelled of gas when not starting so it definitely seemed like it was getting fuel. Soooo, no clue why gas + spark = no start.

[c.u]

Just leve the cam sensor out and let the crank sensor take care of it.

[5_Liter_Eater]

Uh, then it will double start every time and fire in batch mode (if it hasn't been this whole time).