c5z starting issue
Thread Starter
Melting Slicks
Joined: Mar 2010
Posts: 2,301
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From: Los Angeles
c5z starting issue
'04 c5z, all stock, ~40k miles.
It seems lately when I turn the key to start the car, the starter cranks fine, but the motor feels/sounds like it takes a second or so longer than usual to start. Not sure what would be the problem.? Otherwise the car runs fine
I do have a check engine light for that stupid code with the vacuum line check valve thing that runs down to the exhaust manifold (I forget the code # but it's the one that has to do with the valve being behind the block and difficult to change, etc..). It intermittently comes on and goes off but I think it's un-related? That code has something to do with pumping air down into the exhaust manifold to heat up the cats faster? I forget
Do you think it's related? What should I look at?
Thanks
It seems lately when I turn the key to start the car, the starter cranks fine, but the motor feels/sounds like it takes a second or so longer than usual to start. Not sure what would be the problem.? Otherwise the car runs fine
I do have a check engine light for that stupid code with the vacuum line check valve thing that runs down to the exhaust manifold (I forget the code # but it's the one that has to do with the valve being behind the block and difficult to change, etc..). It intermittently comes on and goes off but I think it's un-related? That code has something to do with pumping air down into the exhaust manifold to heat up the cats faster? I forget
Do you think it's related? What should I look at?
Thanks
Last edited by mammoth713; Jun 26, 2018 at 01:18 AM.
Thread Starter
Melting Slicks
Joined: Mar 2010
Posts: 2,301
Likes: 656
From: Los Angeles
It's a habit of mine that I usually turn the car to run, wait a second, and then turn it to start; I'm not literally just putting key in and turning to start immediately.
Only clue so far is it doesn't seem like it's in any way related to starter.. almost seems like a sensor or fuel issue? or idk. Idk even what to begin looking at honestly. But I'm convinced it's not electrical/starter related atleast since the starter cranks fine
I also have a '00 z28 camaro and it has always started immediately once I hit start with the key. (the ls6 vs ls1 are similar designs obviously) I bring up the ls1 camaro because I've never had this issue on that car and it's older and has ~100k miles FWIW. I'm surprised I'm seeing this issue on the vette first
Best way I can describe the issue:
Imagine putting key in, turn to run. Wait a second, turn to start.. starter starts turning motor.. Motor starts spinning but then takes like ~1second longer than you'd think it would to actually fire off
OTHERWISE... car runs, idles, drives, perfectly fine. MPG has not changed. etc...
Only clue so far is it doesn't seem like it's in any way related to starter.. almost seems like a sensor or fuel issue? or idk. Idk even what to begin looking at honestly. But I'm convinced it's not electrical/starter related atleast since the starter cranks fine
I also have a '00 z28 camaro and it has always started immediately once I hit start with the key. (the ls6 vs ls1 are similar designs obviously) I bring up the ls1 camaro because I've never had this issue on that car and it's older and has ~100k miles FWIW. I'm surprised I'm seeing this issue on the vette first
Best way I can describe the issue:
Imagine putting key in, turn to run. Wait a second, turn to start.. starter starts turning motor.. Motor starts spinning but then takes like ~1second longer than you'd think it would to actually fire off
OTHERWISE... car runs, idles, drives, perfectly fine. MPG has not changed. etc...
Last edited by Vetteman Jack; Jun 26, 2018 at 08:59 AM.
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Thread Starter
Melting Slicks
Joined: Mar 2010
Posts: 2,301
Likes: 656
From: Los Angeles
If that is the issue... Does that mean my fuel pump is dying, or what part is on it's way out?
Why would the car run/idle fine?
Drifting
Joined: Aug 2014
Posts: 1,626
Likes: 174
From: North pole
'04 c5z, all stock, ~40k miles.
It seems lately when I turn the key to start the car, the starter cranks fine, but the motor feels/sounds like it takes a second or so longer than usual to start. Not sure what would be the problem.? Otherwise the car runs fine
I do have a check engine light for that stupid code with the vacuum line check valve thing that runs down to the exhaust manifold (I forget the code # but it's the one that has to do with the valve being behind the block and difficult to change, etc..). It intermittently comes on and goes off but I think it's un-related? That code has something to do with pumping air down into the exhaust manifold to heat up the cats faster? I forget
Do you think it's related? What should I look at?
Thanks
It seems lately when I turn the key to start the car, the starter cranks fine, but the motor feels/sounds like it takes a second or so longer than usual to start. Not sure what would be the problem.? Otherwise the car runs fine
I do have a check engine light for that stupid code with the vacuum line check valve thing that runs down to the exhaust manifold (I forget the code # but it's the one that has to do with the valve being behind the block and difficult to change, etc..). It intermittently comes on and goes off but I think it's un-related? That code has something to do with pumping air down into the exhaust manifold to heat up the cats faster? I forget
Do you think it's related? What should I look at?
Thanks
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,500
Likes: 3,999
From: Cape Coral, Florida
Sorry to hear your ride is a little harder to start...if it takes only a second longer to start that might be a little harder to diagnose. My '01 does that very very seldom and I'm not to worried about it unless it takes say 5 seconds to start. It can be fuel related, ignition related, maybe even a crank sensor going a little wonky but without some diagnostic tooling and a little diagnostic knowledge it's basically a crap shoot. Does it do it cold or even after the car has been running ??
Le Mans Master
Joined: Sep 2014
Posts: 5,278
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From: Kelowna BC
Interesting thread...
Me; 04Z, around 50K miles (?), similar non-issue. I wish I could recall when it changed, but my car used to be instant. For some time now it's just a tiny bit of a crank first (nowhere near an actual full second).
Watching, and will try the same 4 second wait...
Me; 04Z, around 50K miles (?), similar non-issue. I wish I could recall when it changed, but my car used to be instant. For some time now it's just a tiny bit of a crank first (nowhere near an actual full second).
Watching, and will try the same 4 second wait...
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Thread Starter
Melting Slicks
Joined: Mar 2010
Posts: 2,301
Likes: 656
From: Los Angeles
IF the cause of your slightly longer crank time is due to fuel pressure bleed off when the engine is OFF, then there can be several possible causes of the pressure bleed off. Could be the pressure check valve is failing, could be a slight leak in the fuel lines between the tank and injectors or could be one or more injectors that are leaking. The pumping portion of the pump is NOT likely the cause of the bleed off. But, unfortunately on the mid year and later 2003 and 2004 C5, the fuel system was changed by GM (new one is dubbed FFS) and the back flow check valve was incorporated into the pump module. Worst part of that is that the on FFS system you have to drop the tanks to get to the fuel pump. Unless you have the tools and skills to do this yourself, it is a very expensive repair mostly due to the labor costs.
As other posters have stated there might be other causes to the slightly longer crank time. My suggestion to wait 4 or so seconds with the key in the ON position before going to the crank position should help narrow down if the cause of your symptom is fuel pressure bleed down or not. Worth a try cause it costs nothing but a few seconds of your time.............
As other posters have stated there might be other causes to the slightly longer crank time. My suggestion to wait 4 or so seconds with the key in the ON position before going to the crank position should help narrow down if the cause of your symptom is fuel pressure bleed down or not. Worth a try cause it costs nothing but a few seconds of your time.............
*Waited 4sec before turning key to "start" on cold motor: still did it
*Waited 4sec before turning key to "start" on warm motor: acted fine
*Waited 4sec before turning key to "start" on cold motor: acted fine
Need more data points. Nothing is conclusive from this yet.
I believe this following information is NOT pertinent to my current symptoms but I'll write it out regardless:
Backstory on battery (for what its worth)
1) (months ago) the battery died, bought new duralast battery
2) duralast battery failedfafter 6 mo and got a new one under warranty
Car doesn't typically sit. I swap between driving this and my '00 z28 to work daily. There was a period I didnt drive the car for 3 weeks and then started it, and it seemed a little weak on starting that particular time. I attributed it to the battery maybe drained a bit. That particular time that it started weak, it had a definite different signature more in line with a weak battery: where the starter kind of sounded like it was having more "trouble" turning over.
In my CURRENT problem, the starter has 0 issue turning and seemingly turns with ease. Thus, I am convinced it is not a battery issue for now. (If that makes sense)
Generally speaking, even with the battery dying, me getting new one, etc... The symtpoms that I'm describing were intermittently present throughout the whole battery saga of new, old, replaced battery, etc.. So I don't think it's related to the battery.
I'm an EE and pretty good with debugging complicated systems.. it's what I do for a living, etc... And for now I'm convinced it's not battery related. So I'm looking for other possible things I could check or consider.
Thread Starter
Melting Slicks
Joined: Mar 2010
Posts: 2,301
Likes: 656
From: Los Angeles
Over past few days I think I have tried it enough that the method of turning the key to run and waiting before starting motor did not yield improved results.
What else should I check?
What else should I check?
Last edited by mammoth713; Jun 28, 2018 at 02:04 AM.
Drifting
Joined: Aug 2014
Posts: 1,626
Likes: 174
From: North pole
just for the gell of it..drivers side the back of the head there is a metal bracket that cuts into the wire harness for the coils,injectors take alook...
Thread Starter
Melting Slicks
Joined: Mar 2010
Posts: 2,301
Likes: 656
From: Los Angeles
Trying to find the cause of an intermittent 1 second longer to start symptom without benefit of an engine analyzer or data logging scan tool is going to be a crap shoot at best. Could be a fuel issue, could be any one of many possible electrical/sensor issues (coils, grounds, cam position sensor, crankshaft position sensor.......) Until it becomes a very prolonged crank, or sets one or more codes or fails to start at all you have a witch hunt in front of you. C5's are very well known for grounding issues so if you need to keep busy hunting, go after all the grounds. Here are a couple ground related links that might help:
http://forums.corvetteforum.com/c5-t...locations.html
http://forums.corvetteforum.com/c5-t...tion-long.html Post #1
Good luck.
http://forums.corvetteforum.com/c5-t...locations.html
http://forums.corvetteforum.com/c5-t...tion-long.html Post #1
Good luck.
Let's say it was a crank or cam position sensor on it's way out... Wouldn't that cause the car to idle funny?
What about injectors.. I don't know anything about injectors and how they actually work. Should I try some kind of gas tank treatment and see if it cleans up the injectors a little or is that a waste of time? I'm wondering if the injectors are playing a part in this somehow.
Is there some kind of corrosion or build up in an injectors that would cause it to not properly deliver fuel on cold starts but then it be fine once the motor is running?
Last edited by mammoth713; Jun 28, 2018 at 11:02 AM.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,500
Likes: 3,999
From: Cape Coral, Florida
I agree with 8Vette...an intermittent problem like yours would be VERY difficult problem to diagnose...a no start is one thing but this is getting a little bit more involved. I have a lab scope and I think even for me to find this problem would be a challenge at best. I'd be looking at a lot of different inputs....Yes, a bad cam/crank would cause the car to idle rough, intermittent stalling, and a host of other things...I think it's the most important sensor in an auto these days and often overlooked in troubleshooting. For a "cranking no start" I like looking to see if I see some RPM movement on the Tach which gets it's signal from the crank sensor...no RPM equals no ignition or fuel injector firing !!...I wouldn't waste your money on fuel injector cleaner for this issue...maybe over the next few days if I have time I'll get a crank / cam waveform off my "01 and see if I can get it when the car doesn't fire on the first crank...I have to get the 2 signals at the PCM being that it's hard to get to both sensors.... so it's a little PITA !!!....now you said it's fine when the engine is warm...that's the only direction we have...you would think it's something "mechanical" but I doubt it !!
p.s. and like I had said my '01 usually starts on the first crank and the few times it does not I don't worry about it !!
p.s. and like I had said my '01 usually starts on the first crank and the few times it does not I don't worry about it !!
Last edited by C5 Diag; Jun 28, 2018 at 11:40 AM.