C5 no start issue

[cammy98]

Hi everyone, I just joined and already have a question if someone can help.
'98 C5, replaced the battery a few weeks ago, and it has been leaving me sit sometime due to a no start. Engine cranks, but does start. When I disconnect the battery overnight and reconnect the negative terminal the car starts right up. Anysuggestions what might be casuing this?

 

[dadaroo]

What is the ACTUAL voltage measured AT the battery before you try and crank it? The C5 will crank with low voltage since it needs high current but the electronics need good voltage. By letting the battery sit disconnected overnight it may be "recovering" some of it's charge.

A fully charged battery should be 12.6v ormore.

It's not 12 volts it's 12.6 because each cell is 2.1 volts.

If the battery is

12.5 = 85% charged
12.4 = 65%
12.3 = 50%
12.2 = 35%
12.1 = drained

 

[timfitz63]

Welcome!

Relative to the line of troubleshooting that "dadaroo" is suggesting: you should read through this thread in the "Technical and Performance" C5 sub-forum, and review the videos it references.

The C5 (like more and more late-model cars) is fussy about batteries, not only the voltage and CCA rating, but also the RC value. If these values are not up to spec on the battery you installed in your C5, it can create a lot of weird issues with the vehicle.

Good luck!

 

[gkayvee]

Welcome!

Relative to the line of troubleshooting that "dadaroo" is suggesting: you should read through this thread in the "Technical and Performance" C5 sub-forum, and review the videos it references.

The C5 (like more and more late-model cars) is fussy about batteries, not only the voltage and CCA rating, but also the RC value. If these values are not up to spec on the battery you installed in your C5, it can create a lot of weird issues with the vehicle.

Good luck!

I had similar, intermittent probs with my '02. I replaaced the stock Group 75 battery with the slightly larger Group 78 and probs vanished. Not sure if it was the old battery acting up or the new one having higher CCA, but no more probs...

 

[cammy98]

C5 no start

I had similar, intermittent probs with my '02. I replaaced the stock Group 75 battery with the slightly larger Group 78 and probs vanished. Not sure if it was the old battery acting up or the new one having higher CCA, but no more probs...

thanks and that is what I think the issue is. I noticed over the weekend the car started and ran fine until I had to start Sun moning and i could hear the fuel pump not running and sure enough wouldn't start. I put a battery charged on and started right up. I have to check my battery (which is new) but will put a group 78 in it.