01 Suburban no spark when it's cold out.

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Feb 29, 2012
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Location
Jasper, AL
01 Suburban K1500
5.3
262k miles
18 degrees F
Trucks runs great but the last 2 mornings it won't start. After it warms up it will start and run fine.
During the no start condition, it has 55 psi fuel pressure, strong battery that turns engine over fast, but does not have spark. To check spark I pulled a plug wire off plug and connected a new plug and grounded the plug threads to the engine block. After about 5 tries it showed spark and immediately started. I shut it off and immediately tried again and had no spark again. I had to go to work so that's all the testing I was able to do.
I have an idea of where to start troubleshooting, but wanted to hear some suggestions from you guys.
 
I was going to suggest cap and rotor but do the 5.3's even have those?
 
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Originally Posted By: zrxkawboy
+1 on the crank sensor.


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My ex fiancée had a Suzuki Reno that wouldn't start in the cold, and here in az cold to us is 27° as a quick fix till u get the part ect, unplug the battery and reconnect it and it should start..... it worked for her car. Had the shop replace the part and now she lives in a freezing climate with no issues.
 
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Well, I tried to warm up the crank sensor with a blowdryer today at lunch and it didn't help. I also swapped around the ignition relay with the starter relay with no luck.
 
Originally Posted By: bama7x57
Well, I tried to warm up the crank sensor with a blowdryer today at lunch and it didn't help. I also swapped around the ignition relay with the starter relay with no luck.




Check for 12 V on the Light Green wire and ground on the Yellow/Black wire to the Crankshaft Position (CKP) sensor.
Test for a 0-12 V square wave signal from the CKP sensor to the PCM, pin 12 of the blue connector, Dark Blue/White wire, when cranking....A Lab Scope is easiest, Lets you see the square wave signal in a graph. An Analog/Digital Volt Meter can be used in a pinch, Just to see if CKP is producing voltage.

Or go the "part changer" route & replace the CKP.
 
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