It’s been a rough journey trying to figure this out. So I rebuilt a 2007 hummer h3 3.7 engine, during the process I dropped the crankshaft on the floor . I know dumb move. I checked the teeth and all and they all looked and seem fine no chips or cracks or anything. After I put it all together and trying to start it it would crank but no start. I took it to the shop . They saying that they did a scope and that one of the teeth is scuffed badly and that’s why the car doesn’t want to start. And that I need to replace the crankshaft. They said they were getting 1 signal out of the 2 and that they can read crank signal. They sent me a pic that I attached on here. I am not a scope expert but isn’t the green like is cam signal? Because usually there are crankshaft and camshaft signals and they have to be like in sync for the engine to start. So i think the yellow is crank and green is cam. Does that mean it’s actually my camshaft sensor or camshaft wiring?? Can someone look at them and give me their opinion. I don’t think it’s the crankshaft because the teeth were barely like affected .

 

I’m definitely not an expert on scopes either, but the yellow is definitely the crankshaft signal and green is definitely the camshaft signal.

The Green (Camshaft) graph, to me, appears to have something wrong with it; I would think it should have more peaks/drops than simply having one and then trailing off.

You said your engine is a 2007; you don’t happen to be using a cylinder head from a 2008+ engine do you? If your cylinder head was originally designed for a 2008+, and is now on a 2007, that means somebody had to machine in the intake camshaft sensor hole, and it is possible that whoever did the work machined it incorrectly and your sensor positioning is all out of whack. This can lead to no/intermittent starting, and this exact thing happened to H3 Humper (on YouTube).

Is this graph measuring the exhaust camshaft sensor, or the intake camshaft sensor?

 

no it’s the original head. 2007. I took it to the machine shop to resurface it and do valve job and such and that’s it.

i don’t honestly know which one does it measure but people been telling me based on the crank diagram which is the yellow meaning I have damaged teeth on the rectular and that’s why it’s not wanting to start. I was planning to replace the camshafts and its wiring connector this weekend . But everyone been saying that even if I did that it still won’t start because the crankshaft teeth are little damaged . I just want to make sure it’s 100% the crankshaft before I take it all apart again