Start issue
Thread Starter
Instructor
Joined: May 2013
Posts: 157
Likes: 24
From: Simpsonville SC
Start issue
I have experienced a stumble start issue from day one. Hope this video clip will load. If it does, I welcome your thoughts.
This is an example of a single....have experience multiple stumbble....3 or 4 tries with a single start button push.
This is an example of a single....have experience multiple stumbble....3 or 4 tries with a single start button push.
Last edited by Coach32; Jan 21, 2019 at 10:14 AM.
Thread Starter
Instructor
Joined: May 2013
Posts: 157
Likes: 24
From: Simpsonville SC
Done that.....no help. On record with GM. Have seen some comments requarding tuner chart adjustments....airflow and fuel mixtures on start, similar to choke adjustments on a carborator. I hate that I’m dealing with this on a brand new car.....maybe it will solve itself after break-in
Burning Brakes
Joined: Nov 2016
Posts: 1,189
Likes: 437
From: San Dimas CA
This shouldn't be too difficult to troubleshoot. I would start by monitoring the voltage to the starter and following the dropout from there.
This is an electrical issue; not a fuel mixture issue.
This is an electrical issue; not a fuel mixture issue.
Last edited by laserdude2215; Jan 21, 2019 at 12:00 PM.
Drifting
Joined: Oct 2005
Posts: 1,352
Likes: 715
From: Terrell North Carolina
Even tho it is a new car, I suspect the battery, or at the least a poor connection at the battery. It sounds to me like while the car is cranking, it is turning over awful slow. As a test, put your battery maintainer on you car to make sure the battery is fully charged, and then do your starting test. If I was the dealer, I would do a starter draw test, & and a battery load test to start ruling out electrical issues.
Keep in mind a 50 mile or less drive is not enough to charge a battery that is in a low state of charge.
Keep in mind a 50 mile or less drive is not enough to charge a battery that is in a low state of charge.
Thread Starter
Instructor
Joined: May 2013
Posts: 157
Likes: 24
From: Simpsonville SC
Even tho it is a new car, I suspect the battery, or at the least a poor connection at the battery. It sounds to me like while the car is cranking, it is turning over awful slow. As a test, put your battery maintainer on you car to make sure the battery is fully charged, and then do your starting test. If I was the dealer, I would do a starter draw test, & and a battery load test to start ruling out electrical issues.
Keep in mind a 50 mile or less drive is not enough to charge a battery that is in a low state of charge.
Keep in mind a 50 mile or less drive is not enough to charge a battery that is in a low state of charge.
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Le Mans Master
Joined: Mar 2010
Posts: 7,049
Likes: 945
From: DFW TX
I don't get alot out of the video, but I can tell you my 14 changes its start up from time to time. I know the C7 has different start delay times based on coolant temp and ambient:
From GM the following are expected start times:
Above 50F may take up to 1.5 seconds
From 14F-49F up to 2.5 seconds
Unless the ambient temperature is -4F or colder it should not take 5 seconds
To the OP: Has it changed with ambient?
From GM the following are expected start times:
Above 50F may take up to 1.5 seconds
From 14F-49F up to 2.5 seconds
Unless the ambient temperature is -4F or colder it should not take 5 seconds
To the OP: Has it changed with ambient?
Moderator emeritus
Joined: Jun 2001
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From: Jacksonville Florida BWO Dayton, Cincinnati, Bloomsbury NJ, Cincinnati
2015 C7 of the Year Finalist
It looks, in the video, that the car hesitates during cranking. It starts fine, then hesitates, the cranks and then runs. That is not good.
Elmer
Elmer
Team Owner
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From: I live my life by 2 rules. 1) Never share everything you know. 2)
St. Jude Donor '11-'12-'13, '16-'17-'18
'member back in the day when the ignition was too far advanced that kind of cranking would happen (or pre-ignition when cranking)?
Le Mans Master
Joined: Mar 2010
Posts: 7,049
Likes: 945
From: DFW TX
I just rewatched the video with better audio (was on a plane earlier)....
Thats crazy that the car starts to crank then stops then does again on its own. Might be fuel related as others have mentioned. Rail pressure not making them makes.
Thats crazy that the car starts to crank then stops then does again on its own. Might be fuel related as others have mentioned. Rail pressure not making them makes.
E-Ray, 3LZ, ZER, LIFT
Joined: Sep 2007
Posts: 34,932
Likes: 12,344
From: NE South Carolina
thanks for the reply.....battery was ruled out by our first guess. It was replaced with a 770 cca Delco.....checked the connections to the battery and have been connected to a battery tender. I should have mentioned preliminary attempt. The conditions have been after a short trip to a gas station....shut off and restart after pumping gas....bump, bump, bump then start. This clip was similar, 20 mile drive, park, atempt to restart, 3 bumps and a second try is the clip you see.......very puzzling. Bad ECM or adjustment, or fuel????
Could be a starter as well.
Last edited by JerryU; Jan 22, 2019 at 06:57 PM.
Race Director
Joined: Mar 2001
Posts: 19,947
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From: Bonneville Salt Flats
I've never experienced this on my '18 I've had for a year and a half. I'd suggest, as others have, faulty starter. I don't see why this would be a big deal for the dealership, or at least a half-*** competent one. Assuming they have access to another correctly starting C7, swap starters and see what happens... duh. 
Thread Starter
Instructor
Joined: May 2013
Posts: 157
Likes: 24
From: Simpsonville SC
Trying to get a field rep/engineer from GM to look at this clip. Short of starting to replace components like the starter or the ECM.....seems a trouble shooting process should isolate the problem.
Thread Starter
Instructor
Joined: May 2013
Posts: 157
Likes: 24
From: Simpsonville SC
The dealership wants to take possession of my car for as long as it takes to find the problem. I have a problem handing the keys to my car over for as long as it takes. The car starts find 90% of the time. I have captured this video clip of a single stumble even though I get a triple stumble at times. I don’t understand why it can’t be diagnosed. Tech. Thinks it is the starter but can’t get them to just replace the components that could cause this. My have to continue driving the car until I get a complete failure.
Le Mans Master
Joined: Mar 2010
Posts: 7,049
Likes: 945
From: DFW TX
The dealership wants to take possession of my car for as long as it takes to find the problem. I have a problem handing the keys to my car over for as long as it takes. The car starts find 90% of the time. I have captured this video clip of a single stumble even though I get a triple stumble at times. I don’t understand why it can’t be diagnosed. Tech. Thinks it is the starter but can’t get them to just replace the components that could cause this. My have to continue driving the car until I get a complete failure.
Le Mans Master
Joined: Oct 2014
Posts: 8,672
Likes: 2,726
From: Atlanta GA
Dave
Thread Starter
Instructor
Joined: May 2013
Posts: 157
Likes: 24
From: Simpsonville SC
Had the car out yesterday and it never scripted a beat....puzzling.....did some reach on micro relay problems with the starter relay, fuel pump relay, & engine control module. These are located in the fuse panel, passenger side engine compartment. I feel I have a better chance of identifying the problem than allowing some knucklehead driving my car around looking for the starter to stumble the same way I showed in this video clip. Their plug-in shows zero faults, the battery and alternator show healthy. You would think proper trouble shooting would identify a weakness. Trying to get a GM field engineer to take a look but I'm way down on the priority list.
Burning Brakes
Joined: Apr 2014
Posts: 854
Likes: 302
From listening to the video, it seems like the starter disengages the re-engages until lift off. so, what would cause the starter to disengage? The load on the starter should not change other than temperature causing more drag from thick oil. The mechanical HPFP is another source of drag, but the starter and engine don't strike me as something that would sporadically cause high drag one moment and not the next. Even if there was a lot of continual drag, starters stay engage even with locked engines. So I would rule out engine and HPFP issues. Next is the starter's engagement mechanism - say it is weak and it pops off the flywheel? I'd rule that out too as I don't hear any starter overrun. Lastly is the command to the starter solenoid and the solenoid itself. Which is where I'd be looking. Does the starter lose and re-engage the command to start, or does the solenoid drop out even though the car is commanding it to engage. The latter means change the starter assembly. The former means digging into the electrical/electronic side of things. IMO this has nothing to do with the fuel side.