Cam Position Sensor?
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Cam Position Sensor?
I was wondering why my truck wont start sometimes. It only happens when its colder outside. I check the fuel pressure and the pump was fine, and it held pressure over night. It will crank forever but won't fire. The other thing I was thinking about was the cam position sensor. I got a code for it probably 5 months ago but it never gave me a problem. Now it won't start at all. Does anyone have a idea if that is what the problem is or is it something else?
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Joined: Jan 2001
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From: Central NYS
When it won't start, see that the CEL lights with the key in the "ON" position. Then turn the key to the "Crank" position and crank it. If the CEL stays on, the PCM hasn't seen a crankshaft position (CKP) sensor signal. (The PCM needs that signal to figure out WHEN to fire WHICH sparkplug.) If the CEL goes out while cranking it indicates the PCM saw a CKP signal, and we gotta look someplace else for the no start condiction.
The camshaft position (CMP) sensor is used by the PCM to figure out WHICH fuel injector to fire, since the cam turns half the speed of the crankshaft (i.e, if cyl #1 is reported to be at TDC by the CKP sensor, the fuel injector driver needs to know if that is TDC on the compression stroke or TDC on the exhaust stroke.) If the PCM doesn't see a CMP sensor signal, it will try a couple of patterns to try and stumble on the correct injector timing. Once the engine starts, it doesn't need the cam postion sensor.
The camshaft position (CMP) sensor is used by the PCM to figure out WHICH fuel injector to fire, since the cam turns half the speed of the crankshaft (i.e, if cyl #1 is reported to be at TDC by the CKP sensor, the fuel injector driver needs to know if that is TDC on the compression stroke or TDC on the exhaust stroke.) If the PCM doesn't see a CMP sensor signal, it will try a couple of patterns to try and stumble on the correct injector timing. Once the engine starts, it doesn't need the cam postion sensor.
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Thanks, I'll try it when it acts up again. Later that same day it gave me the problem it started up fine, when the temp outside was warmer. I don't know if that has anything to do with it but that's what happens every time.
