won't start: how to test timing chain?

(99 Cavalier 2.2L) Suddenly won't start. Going through spark, fuel, sensors, etc, and not finding anything so far.

Not that I think this is the problem, but, is there a way to tell if the timing chain has jumped? (There is no distributor.) All I can think is to watch the valves and feel the piston with a wire? And, it seems like that would be to crude to be useful.

Maybe, is there some know timing between the Crank and Cam position sensor pulses?

Thanks, George

Reply to
George
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you'd have to remove the timing cover and check where the timing marks are.. Do you have fuel pressure? I don't know if the Cavilier has a fuel cut off switch or not.

Reply to
m6onz5a

Dual trace lab scope on the crank and cam sensors, should be easy to spot.

Reply to
aarcuda69062

Compression test may help. See if all cylinders are way down.

Reply to
Paul

Thanks. Do you know what the timing relationship is? Like, leading edges match, or what? Those wires are not easy to get to (the pickups are down on the back of the block), so I'd like to know what I'm looking for before crawling in.

G
Reply to
George

Well, not pressure, per se. I'm having a lot of trouble separating the 'quick disconnect' (HA!) fittings on the fuel lines.

But, I pulled the fuel rail/injector assembly, and the injectors squirt. So, I think fuel is OK.

What else I'm getting is a strange action in the starter, where the overrunning clutch seems to break free after a short crank. It's hard to be sure what's going on, but there may be a sort of 'clang' from the engine at the same time. (There's a lot going on, and most of it is bad. And it's cold out.)

Anyway, that's one reason I suspect the valve timing.

G
Reply to
George

Sent to your e-mail

It might be easier to obtain the cam sensor signal at the PCM (terminal #"7" brown & white wire) and the crank sensor at the ignition control module (terminal "A" solid purple wire)

Reply to
aarcuda69062

If you've done this (or similar), what do you use to probe the wires? I've been using syringe needles. They're very sharp, and get through the insulation well, but I have to hold them in place. It would be a little awkward to do that, and reach from the PCM to the ign module.

G
Reply to
George

I back probe the terminal at the connector,

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piercing the wire would be a last resort, if that's the case, I use a bed of nails type alligator clip.

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Reply to
aarcuda69062

I had a similar problem

was a crack in the crank position sensor problem is that to check it you will wind up breaking the sensor since they are fragile to begin with. The cost was reasonable so i would start there

if your rotor spins your timing belt works / off time is another story

see if it will start with ether

Reply to
Ray

That's an appealing thought. Did you have spark?

No rotor. If it had one, checking the cam timing would be a lot easier.

G

Reply to
George

It's a lot easier to probe the ign module connector than it is the PCM. Of course, there's no cam sensor signal at the ign module. But, there are two signals from the PCM, called "Ignition Control A & B" in my book. Since the PCM only has the cam signal to work with, I'm guessing that these are derived from it.

In any case, they appear sync'd with the crank signal. (Leading edge is centered on the zero-cross of a crank pulse.) ...

Ign .------. .--- control ______| |______________________________________| . crank ____/\. ___/\ ___/\ /\ ___/\ ___/\ ___/\ ___/\ __ \/ \/ \/ \/ \/ \/ \/ \/

(view with fixed-pitch font)

I'm thinking that this looks pretty 'reasonable', but I really don't know. Would anyone know whether this is indicating that the cam timing is OK?

G
Reply to
George

Well, it now starts. After I replaced the starter. Which failed (bad bearing, it felt like) while cranking the engine to test various theories of why it wouldn't start.

I will swear that the starter was cranking OK when we started. But, I replaced it, and now it starts. I hang my head in embarrassment.

Thanks to all who contributed.

G
Reply to
George

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