Confirmation that crank signal is bad
Thread Starter
Teching In
Joined: Oct 2011
Posts: 4
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Confirmation that crank signal is bad So my 01' Trans Am WS6 stock 5.7L LS1 has been having an issue with stalling out some time after the car starts, usually just enough time to get me a few miles from home, and then won't re-start, it just cranks and cranks. If I leave it sit for say maybe greater than 8 hours, it will start up again just fine. So reading thru the interwebz, I've begun to suspect the crank sensor, and took some measurements with an oscilloscope to try to confirm that this is the issue before I just start replacing parts randomly.
I would like to know if you guys think that the crank sensor is the primary culprit or something else.
Video showing what I presume to be a normal trace of crank signal
Video of the car stalling out ( I can't beleive I was filming when it happened!)
Here is a cranking attempt from inside the car after the car stalled out
Another cranking attempt this time measuring the crank signal
Video of my o-scope setup
I would like to know if you guys think that the crank sensor is the primary culprit or something else.
Video showing what I presume to be a normal trace of crank signal
Video of the car stalling out ( I can't beleive I was filming when it happened!)
Here is a cranking attempt from inside the car after the car stalled out
Another cranking attempt this time measuring the crank signal
Video of my o-scope setup
Thread Starter
Teching In
Joined: Oct 2011
Posts: 4
Likes: 0
I tested the fuel pressure previously and it was 53psi during initial prime, then 56psi while running and all thru the stalling out, and was in that same range while cranking afterwards and not starting. Thanks for the input!
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
You need to increase the time base and capture more signal, then compare it to this (you need both CKP and CMP so you can compare their relative positions):
the crank reluctor is divided into 4 quadrants, each quadrant has a unique sequence of wide (12°) and narrow (3°) pulse pairs.
the crank reluctor is divided into 4 quadrants, each quadrant has a unique sequence of wide (12°) and narrow (3°) pulse pairs.
