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no start after head rebuilt. Think may be starter Help.

Old 06-13-2018, 10:01 AM
  #21  
C6Z06Silverbullet
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Originally Posted by ldscamaross View Post
Another update guys. Tonight i did the jump the starter relay trick. I took the plastic cap of the relay and connected the contact points of the relay. The starter cranked the engine and it was strong like normal. While at it I also had my dad in the car to see if I could get the engine to fire with manually cranking/ jumping the starter. I had him hit the igntion button and then i jumped the starter. The engine fired and ran for about 2-3 seconds and then died. I tried it again and same result.

My conclusion from this is that the engine was getting fuel and spark at the right time so fuel pressure good, injectors firing, spark timing firing ect. It also seems like the wiring from the battery to the starter is good and the grounds at least some back to the battery are good. I have swapped out a couple "good" starter relays meaning they worked and started the engine on my other car so I dont think it is the relay.
It seems for some reason the computer isnt giving the command to fire the starter and if it is manually done the car will run for a few seconds and then die. This problem seems to get more and more complex, haha.

Also I still cant get a connection with the obd2 code reader. it powers up but wont communicate with the ecu.

Do you guys have any new thoughts?

Thanks again in advance.
Well now it sounds like an ECM problem for sure.
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Old 06-13-2018, 02:03 PM
  #22  
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Originally Posted by ldscamaross View Post
Battery voltage was 12.22 when I checked terminals. The lcd screen in the car said 11.8v
12.1 volts is considered a completely dead battery. At 12.2, you'll have a really hard time cranking any car, let alone a high compression LS7.

Charge that battery up to full (12.7-12.8).
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Old 06-13-2018, 06:26 PM
  #23  
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Originally Posted by Must_Have_Z View Post
12.1 volts is considered a completely dead battery. At 12.2, you'll have a really hard time cranking any car, let alone a high compression LS7.

Charge that battery up to full (12.7-12.8).
are you sure bout that? I believe that is normal until the alternator kicks in and the voltage hovers around 14ish. The faulty suspect is something to do with that scanner not hooking up in my opinion. Just my 2c
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Old 06-13-2018, 06:29 PM
  #24  
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Is your code reader battery powered or does it use the power from the port it's plugged into. Did you confirm the 15 amp ECM fuse had power in and out? POWER, NOT OHM OUT THE FUSE FOR CONTINUITY.
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Old 06-13-2018, 07:52 PM
  #25  
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His battery is fine! (Does need a charge though)If you read his post correctly he jumped the solenoid and the car started for a few and died. Between that and the obd2 connector not working I'm betting it's an ecm problem. Again I'm guessing. Just putting the facts together. Do you have any reputable shops around you that do tuning? If so take them your ECM and have them check it out. At least that way you will know if the ECM is the problem or not.

Last edited by C6Z06Silverbullet; 06-13-2018 at 07:55 PM.
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Old 06-13-2018, 08:44 PM
  #26  
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This would probably go much quicker If he'd check the simple things he's been asked to check. Asked to check for power at the output terminal of the alternator. Should be hot all the time. No power and he blew the fuseable link. Still hasn't confirmed power where he's been asked to at the fuse block. Excuse me while I go spank the monkey
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Old 06-13-2018, 09:30 PM
  #27  
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Battery is at 12.8 now and is fine. As far as the code reader I am using one from autozone as well as hptuner. when I plug in the obd2 port the reader comes on so I am assuming it has power. I also have a obd2 reader that I use with my android phone that is powered by the car. I can try that.

Battery voltage is high 12 until alternator comes on. The it is around 14v when running

I haven't confirmed the ecu has power from the fuse panel. If the car cranks and fires meaning the fuel injectors cycled and the spark was sent at the right time for combustion doesnt that mean the ecu is getting power?

I do have two shops around that do tuning. Im in West Jordan Utah. Im leaning towards an ecu or some computer not working right. I havnt touch any wire going from the obd port to the computer and I was able to connect to the computer before and pulled misfire codes.

I have power at the fuse block. Also on one of the 4 pins for the starter relay in the fuse box. 12 volts all other ones have no power. If you were to draw a rectangle where the relay goes and staning in front of the car looking down at the fuse panel the pin with power all times is the upper left side of the rectangle.

As far as checking all the simple things I am also trying to problem solve this and I dont know why checking the positive output terminal of the alternator is going to show me why I cant connect to the obd port and why the computer isnt sending a signal to the starter relay to crank the car. I have checked ground from the battery forward as asked. I jumped the starter as asked which actually gave me new info and ruled out several possibilities. I have checked every fuse, and every relay in the fuse box. If a fusable link was bad I wouldn't be able to jump the starter relay and have the starter crank would I?

I think we need to move on from grounds, starter solenoid, power from the battery to starter and focus on the new info we have.
The car is getting power, the computer is at least partially working to run the engine for a few seconds.

I don't mean to be critical if that is how it comes across and I thank everybody for the suggestions they have given.

Last edited by ldscamaross; 06-13-2018 at 09:33 PM.
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Old 06-13-2018, 11:04 PM
  #28  
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Have you tried swapping the ignition switch?
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Old 06-13-2018, 11:06 PM
  #29  
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First off...I've red the entire thread. Look at the history. Car started and ran fine BEFORE head swap. AFTER head swap, car won't start as before. Meaning something was damaged or a component took a dump DURING head swap procedure. Retrace the affected area and ensure all electrical connections are correct and UNDAMAGED. If nothing is visible...or jumping out at you, based on everything else you've discussed as accomplished, maybe the ignition switch took a dump. That's a stretch I know...but all signs point to an electrical malfunction in the ignition/starter system. Especially when you said you could jump it. That means you BYPASSED the ignition switch to start the car...and it ran. I think you identified at least part of the problem right there. These cars are notoriously sensitive to electronic issues. I would bet a paycheck it's NOT an ECM issue as these will normally manifest themselves completely differently.
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Old 06-14-2018, 09:29 AM
  #30  
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Old 06-14-2018, 12:14 PM
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Originally Posted by JesC6Z View Post

are you sure bout that? I believe that is normal until the alternator kicks in and the voltage hovers around 14ish. The faulty suspect is something to do with that scanner not hooking up in my opinion. Just my 2c
12.2 is NOT normal. That is about 30-40% charged. It sounds like your battery is not the cause, but 12.2 volts is too low of a standing voltage for a Corvette. It needs to be around 12.5-12.7 for best starting performance (once you fix your issue).

https://www.yourmechanic.com/article...-a-car-battery
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Old 06-14-2018, 01:11 PM
  #32  
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Looking at the schematic posted above by Javvy, I think you have an issue with the clutch pedal start switch.



You mention that you get power at one of the starter relay pins. Which pin exactly? I am willing to bet its pin C4. Looks like you are not getting power to B4 of the starter relay. If you have no power at B4, that little arrow will not flip over to complete the circuit for power delivery to the starter solenoid contacts, as well of course, you won't have power to the BCM.


Press in the clutch and see if you get power at pin B4 of the starter relay when starting.

I'm not sure on the procedure for clutch re-learn, but I'm pretty sure the sensor itself is pretty cheap.


I have outlined this in red below:


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Old 06-14-2018, 05:58 PM
  #33  
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Using a test light, battery connected and car switched on, list every fuse that does have power (on both sides) and every one that does not. If I'm reading this correctly you say some did not have power.
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Old 06-14-2018, 08:12 PM
  #34  
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Hey guys I finally figured it out. Last night I was looking at the wire path for the can bus wires and they start at the obd port, go through the bcm, through onstar and through the BRAKE CONTROL MODULE and then to the ecu. When doing the head swap I disconnected the brake control module bcm. When I found it today it was connected like normal latched and everything. I remember that it was a little difficult to get back in before. I took it back out and looked at it and all pins were good and it was clean ect. I put it back and it was still a little difficult. I tried one more time and it slid in smoothly. The cranked it and it starter right up. It looks like the can wires weren't connecting for some reason even though the connector was fully seated. So for future if any body has a similar issue trace the can bus wires through the system and make sure the signal can get from one end to the other. Remember I also couldn't get the obd to talk with the ecu. The scanner connected today and I was able to pull codes. I had a fan code because my fan isnt connected yet. Hurray.

Thanks again for all your guys help. This is a great forum.
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Old 06-14-2018, 08:21 PM
  #35  
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Old 06-15-2018, 07:50 PM
  #36  
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Originally Posted by 390amx1 View Post
Suggest you don't over think this. Occums razor. If it worked before you f'ed with it, then something didn't go back together correctly or you have a discharged battery...
Post #2. Wish I could take credit for this but someone beat me to it.
We knew nothing about this other stuff you took apart so who could know? This is why questions are asked that might seem unrelated because in reality, it all matters. Especially from a thousand miles away.
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Old 06-15-2018, 08:07 PM
  #37  
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Wonderful!

edit: but why disconnect that harness for doing a head swap?

Last edited by JesC6Z; 06-15-2018 at 08:08 PM.
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Old 06-15-2018, 08:19 PM
  #38  
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Originally Posted by JesC6Z View Post
Wonderful!

edit: but why disconnect that harness for doing a head swap?
I also had to remove the steering rack to take off a broken inner tie rod. That harness was disconnected to releave tension so i could move the brake controller up and out of the way.
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