C5 spin no start
Thread Starter
Intermediate
Joined: Sep 2021
Posts: 41
Likes: 2
C5 spin no start
Got an interesting issue. My 04 C5 will, about 1 out of 5 times, spin with no start or will fire but stumble and die immediately. Once it does this, I can spin it for as long as i want with no hint of starting. If I cycle the key a few times eventually it will start and run no issue.
It has the issue when it is cold or after it has been sitting for over an hour or so, never when just been running, It acts like no fuel.
Changed the ignition switch due to other issues. Thought maybe it would have an impact, no change.
Seems to me pump is good, so has to be something in between. I sure hope so, 04 is a bear to replace.
C5 has no fuel pump relay that I can find, just a fuse. Looked over wiring and grounds that i can get to. All are tight and clean.
Any ideas would be appreciated.
thanks in advance
It has the issue when it is cold or after it has been sitting for over an hour or so, never when just been running, It acts like no fuel.
Changed the ignition switch due to other issues. Thought maybe it would have an impact, no change.
Seems to me pump is good, so has to be something in between. I sure hope so, 04 is a bear to replace.
C5 has no fuel pump relay that I can find, just a fuse. Looked over wiring and grounds that i can get to. All are tight and clean.
Any ideas would be appreciated.
thanks in advance
Tech Contributor
Joined: Jan 2007
Posts: 19,115
Likes: 1,038
From: Dyer, IN
Got an interesting issue. My 04 C5 will, about 1 out of 5 times, spin with no start or will fire but stumble and die immediately. Once it does this, I can spin it for as long as i want with no hint of starting. If I cycle the key a few times eventually it will start and run no issue.
It has the issue when it is cold or after it has been sitting for over an hour or so, never when just been running, It acts like no fuel.
Changed the ignition switch due to other issues. Thought maybe it would have an impact, no change.
Seems to me pump is good, so has to be something in between. I sure hope so, 04 is a bear to replace.
C5 has no fuel pump relay that I can find, just a fuse. Looked over wiring and grounds that i can get to. All are tight and clean.
Any ideas would be appreciated.
thanks in advance
It has the issue when it is cold or after it has been sitting for over an hour or so, never when just been running, It acts like no fuel.
Changed the ignition switch due to other issues. Thought maybe it would have an impact, no change.
Seems to me pump is good, so has to be something in between. I sure hope so, 04 is a bear to replace.
C5 has no fuel pump relay that I can find, just a fuse. Looked over wiring and grounds that i can get to. All are tight and clean.
Any ideas would be appreciated.
thanks in advance
Your owners manual explains exactly where the fuel pump relay is, as does the back of the underhood fuse box cover.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,191
Likes: 3,874
From: Cape Coral, Florida
While the car is cranking look at your Tach and if it doesn’t move this may point to a bad crank sensor…with key on do you hear the pump run for 2 seconds and shut off ??
Last edited by C5 Diag; Aug 22, 2024 at 11:39 AM.
Thread Starter
Intermediate
Joined: Sep 2021
Posts: 41
Likes: 2
checked the relay, swapped for one of the other ones. When I googled the fuses got a different one back. Gotta find an owners manual, didn’t get one with the car.
When I hear it, it cranks.
tach doesn’t seem to move when it cranks, fires up on just about first rotation when it is good. Have to wait to see when it fails next
thank you guys for the quick replies.
When I hear it, it cranks.
tach doesn’t seem to move when it cranks, fires up on just about first rotation when it is good. Have to wait to see when it fails next
thank you guys for the quick replies.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,191
Likes: 3,874
From: Cape Coral, Florida
If you turn the key on and hear the pump run for 2 seconds
it’s not the fuse…a crank no start is easy to diagnose…you just need to follow a diagnostic process…when you say “when I hear it, it cranks”…do you mean when you hear the fuel pump it “starts” ??…verbiage is important when describing this.
it’s not the fuse…a crank no start is easy to diagnose…you just need to follow a diagnostic process…when you say “when I hear it, it cranks”…do you mean when you hear the fuel pump it “starts” ??…verbiage is important when describing this.
Last edited by C5 Diag; Aug 22, 2024 at 12:44 PM.
Melting Slicks
Joined: Nov 2014
Posts: 3,399
Likes: 1,338
From: Havre de Grace Maryland
Do not know your electrical or mechanical skills, but the C5 is a 'Rubix Cube' challenge to find what the problem is if you are not proficient in both. Before throwing money and parts at the problem, it may be more efficient and economical to let experts sort out the problem and fix it. A good source to find experts is from your local Corvette Club. JMHO.
Thread Starter
Intermediate
Joined: Sep 2021
Posts: 41
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Sorry, you are right, verbiage does matter.
So far, I hear the fuel pump every time and every time it has started no issue. I didn’t think it was the fuse as that tests good but I think it could still be an intermittent issue with the relay. It has not failed -yet- so if/when it does I will be able to add what I heard just before.
thanks to you and everyone that has given ideas/knowledge. It really helps and I appreciate it.
So far, I hear the fuel pump every time and every time it has started no issue. I didn’t think it was the fuse as that tests good but I think it could still be an intermittent issue with the relay. It has not failed -yet- so if/when it does I will be able to add what I heard just before.
thanks to you and everyone that has given ideas/knowledge. It really helps and I appreciate it.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,191
Likes: 3,874
From: Cape Coral, Florida
Well when it cranks but doesn’t start look at the Tach…if you hook up a fuel pressure gauge while cranking and if it is the crank sensor you will see the fuel pressure drop while cranking.
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Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,191
Likes: 3,874
From: Cape Coral, Florida
If no ignition pulse from crank sensor fuel pump will stop working…you will not have control side feed power to the fuel pump relay…if after 2 seconds PCM sees crank sensor signal fuel pump relay control side feed remains energized.
Thread Starter
Intermediate
Joined: Sep 2021
Posts: 41
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Everyone, thank you for the help.
it was the Fuel Pump Relay (#35 on the chart). I swapped it for another and it had no issues, replaced the original and it re-occurred. Think this one is solved.
I really appreciate the information and discussion, it made this an easy fix.
Thanks again
Ron
it was the Fuel Pump Relay (#35 on the chart). I swapped it for another and it had no issues, replaced the original and it re-occurred. Think this one is solved.
I really appreciate the information and discussion, it made this an easy fix.
Thanks again
Ron