HELP - No cam signal -
HELP - No cam signal - Took engine out. Fixed head gasket. Put back in. Wont start. Turns over really hard like an engine with a ton of timing.
*found broken ground wire on back of head. Fixed it.
*Still wont start
*Logged all the sensors. Found no cam signal from high to low, and no signal from low to high. Swapped cam sensor. Inspected connector, good....... Still no cam signal and no start????????????
*How many grounds are back behind the head? Its a nightmare to see back there and do anything. Is this likely what it is? Grounds messed up on the back of head? I'll have to drop the engine again to get them if so.
*found broken ground wire on back of head. Fixed it.
*Still wont start
*Logged all the sensors. Found no cam signal from high to low, and no signal from low to high. Swapped cam sensor. Inspected connector, good....... Still no cam signal and no start????????????
*How many grounds are back behind the head? Its a nightmare to see back there and do anything. Is this likely what it is? Grounds messed up on the back of head? I'll have to drop the engine again to get them if so.
Last edited by pwrtrip75; Jul 27, 2012 at 07:11 PM.
In my experience, the cam sensor won't cause your hard cranking issue. It'll cause a no-start condition when the cam phase isn't right though.
What does your tach do when you're cranking it over?
What does your tach do when you're cranking it over?
I fished the entire harness up out so I can get to it, I cut the grounds off the back of the head. Im just going to redo them, extend them, and ground them somewhere that I can get to.
Still like to know how the cam sensor circuit works.... anyone? Grounds even related?
Still like to know how the cam sensor circuit works.... anyone? Grounds even related?
I dug into the cam sensor stuff a couple years ago trying to help out a buddy. Here's what I recall going off of memory:
On an LS1/LS6, the cam sensor reads a gear on the back of the motor that tells the PCM which stroke the engine is on. If the cam sensor isn't working, the computer always assumes its on cycle A. If its actually on cycle B, the exhaust will burble and pop and the car won't start. If you stop cranking and the motor is sitting on cycle A, it'll fire right up like nothing is wrong.
That being said, we tracked his issue down every which way and chalked it up to a broken cam sensor gear on the cam, and we still didn't fix it. So there's a chance that's all related to the bad PCM mentioned in the other thread, but we swapped PCM's to no avail.
On an LS1/LS6, the cam sensor reads a gear on the back of the motor that tells the PCM which stroke the engine is on. If the cam sensor isn't working, the computer always assumes its on cycle A. If its actually on cycle B, the exhaust will burble and pop and the car won't start. If you stop cranking and the motor is sitting on cycle A, it'll fire right up like nothing is wrong.
That being said, we tracked his issue down every which way and chalked it up to a broken cam sensor gear on the cam, and we still didn't fix it. So there's a chance that's all related to the bad PCM mentioned in the other thread, but we swapped PCM's to no avail.
On my 2002 no cam signal caused no tach, and the MIL came on. Car started and ran fine. My problem was hungry pack rats. On mine the sensor picks up a magnetic signal from the 4th cam bearing journal.
Al 95 Z28, 02 Z28, 73 Z28
Al 95 Z28, 02 Z28, 73 Z28
I dug into the cam sensor stuff a couple years ago trying to help out a buddy. Here's what I recall going off of memory:
On an LS1/LS6, the cam sensor reads a gear on the back of the motor that tells the PCM which stroke the engine is on. If the cam sensor isn't working, the computer always assumes its on cycle A. If its actually on cycle B, the exhaust will burble and pop and the car won't start. If you stop cranking and the motor is sitting on cycle A, it'll fire right up like nothing is wrong.
That being said, we tracked his issue down every which way and chalked it up to a broken cam sensor gear on the cam, and we still didn't fix it. So there's a chance that's all related to the bad PCM mentioned in the other thread, but we swapped PCM's to no avail.
On an LS1/LS6, the cam sensor reads a gear on the back of the motor that tells the PCM which stroke the engine is on. If the cam sensor isn't working, the computer always assumes its on cycle A. If its actually on cycle B, the exhaust will burble and pop and the car won't start. If you stop cranking and the motor is sitting on cycle A, it'll fire right up like nothing is wrong.
That being said, we tracked his issue down every which way and chalked it up to a broken cam sensor gear on the cam, and we still didn't fix it. So there's a chance that's all related to the bad PCM mentioned in the other thread, but we swapped PCM's to no avail.
The car blew a head gasket, then still ran and I drove it about 45 seconds and shut it off. It still idled fine. I dont think i damaged anything then...
When I found the broken ground on the back of the head, before i fixed that when i turned the ignition on all the gauges would bounce back and fourth once then the gas gauge would sit there and pulse back and fourth. I fixed the ground and the gauges all went to normal.... but still this issue.
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I took the whole harness off, cut the grounds off on the back of the head and spliced in longer ones to attach elsewhere. Also inspected the whole harness, all looks good....?
Put it back together... No cam signal. Replaced cam sensor again with one I know works... Nothing. Replaced the PCM..... Nothing.
I dont really know what to do now. ??
I also checked the terminal for the cam sensor, it has 12v on one, a low voltage on the other and nothing in the middle... Just like what the schematics say it should be. Im so lost. ??
http://www.chevythunder.com/Engine_c...CMP-CKP-KS.gif
Put it back together... No cam signal. Replaced cam sensor again with one I know works... Nothing. Replaced the PCM..... Nothing.
I dont really know what to do now. ??
I also checked the terminal for the cam sensor, it has 12v on one, a low voltage on the other and nothing in the middle... Just like what the schematics say it should be. Im so lost. ??
http://www.chevythunder.com/Engine_c...CMP-CKP-KS.gif
Last edited by pwrtrip75; Jul 27, 2012 at 08:06 PM.
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Verdad Gallardo It still wont start but I logged it again.. this time the cam sensor signal did change. It turns over and I get a random pop out the exhaust. Error codes below. Maybe whatever was wrong with the cam sensor I fixed. But the POS still wont start. 
Also just sprayed starting fluid in it and it does fire. Injectors must not be working. There is 12v there at the injector though ??????????????????? And the log shows the PCM firing them.
Also just sprayed starting fluid in it and it does fire. Injectors must not be working. There is 12v there at the injector though ??????????????????? And the log shows the PCM firing them.
Last edited by pwrtrip75; Jul 27, 2012 at 08:06 PM.
Also took the harness apart again, tested the continuity between all the cam sensor wires and the connection at the PCM, I had logged it again and the cam sensor signal hi to low and low to hi remained at 0 when cranking.......... What is this supposed to do? But all the wires are good and reading good.
So lost here. Car still will not start and have no clue what to do next.
Also when it fired with starting fluid, did once, wont anymore. All the plugs on just the passenger side were carboned up, the drivers side looked good yet. ??
When it fired with starting fluid, did it run long enough for you to hear if there was a heavy misfire? The hard cranking thing makes it sound like a mechanical issue to me.
If it were me and I was troubleshooting the no-fire issue, I'd hook up a test light on a plug wire and see if it's getting spark. If it is, next I'd lift the fuel rails and see if the injectors are firing while cranking. That would at least give you a little direction for troubleshooting the no-fire.
If it were me and I was troubleshooting the no-fire issue, I'd hook up a test light on a plug wire and see if it's getting spark. If it is, next I'd lift the fuel rails and see if the injectors are firing while cranking. That would at least give you a little direction for troubleshooting the no-fire.
When it fired with starting fluid, did it run long enough for you to hear if there was a heavy misfire? The hard cranking thing makes it sound like a mechanical issue to me.
If it were me and I was troubleshooting the no-fire issue, I'd hook up a test light on a plug wire and see if it's getting spark. If it is, next I'd lift the fuel rails and see if the injectors are firing while cranking. That would at least give you a little direction for troubleshooting the no-fire.
If it were me and I was troubleshooting the no-fire issue, I'd hook up a test light on a plug wire and see if it's getting spark. If it is, next I'd lift the fuel rails and see if the injectors are firing while cranking. That would at least give you a little direction for troubleshooting the no-fire.
I dont think i can lift the rails....all the injectors would blow out. Thats what I am guessing is either the injectors are not timed right or not all firing. Everything worked fine prior to the head gasket failure.
Based on looking at the plugs, My guess is the drivers side bank of injectors are not fully working or working intermittently. But they have power to the injector wires. If the PCM wasnt switching them... Not sure. I replaced the PCM, I replaced the cam sensor, I replaced the crank sensor.... still nothing.
I am not sure how to diagnose this further? If it had a broken injector signal wire in the harness... one injector would not work right? It would run and misfire. But have it so it wont even start? I dont get it.
I also just checked the voltage at the injectors. Of the 2 wires going to each injector one of them has 12.2 volts to ground. Then if you check the two wires to each other there is 6 volts in between them on all of them. .. this is with just the ignition on. Is this normal? Why would there be any ground there if the injector is not being switched?
This makes no sense to have a constant ground that has 50% resistance. ???
This makes no sense to have a constant ground that has 50% resistance. ???
If you're checking resistance/continuity with a DVOM, this will probably give inaccurate ground readings. IIRC, I ran into this same sort of issue on a friends swap, where we were trying to probe pcm controls to relays for adding electric fans to his swap. We would get some sort of messed up reading (iirc,6volts) on the "ground" side of PCM relay control outputs. I was later informed that the grounding of the PCM controls is of a "floating" ground nature, and that a DVOM will interpret this incorrectly.
I'm not sure if this is the same issue that you're running into, but it might be.
I'm not sure if this is the same issue that you're running into, but it might be.
Also just checked continuity of all the injector wires to the PCM... all good. And just did the crank sensor wires also. All good. ??? I dont know what else to do.
What else is there?
What else is there?
Back to basics time. I know it's probably going to sound crazy....but "fuel pressure,compression,and spark". You've already checked what is reasonable....maybe its time to take a step back to the basics?
I seen a post on a "crank relearn" ... never heard of it.. Found one post it said hard starting and stuff. Could it be? No idea what this is and cant find a procedure. Can HP Tuners handle this?
I have stock PCM HP Tuners 2 bar SD, and some Billet atomizer 160 lbs/hr injectors that took some major tweaking to get them to start and run. So if it is this "crank relearn" problem it might be more of a problem on mine than others.....not even starting. ??? im just grasping at straws now i have no experience with that... sound logical? Anyone?
Last edited by pwrtrip75; Jul 29, 2012 at 10:01 PM.
