C5 Hard start, DIC is displaying battery at 11.9 volts.
07-20-2018, 07:32 PM
#1
Racer
Thread Starter
C5 Hard start, DIC is displaying battery at 11.9 volts.
In my '99 when I turn the key into the run position DIC says battery volts is 11.9 is this normal and would this cause a hard start? The hard start only ever occurs when the car is left sitting overnight or is able to cool down. After driving for a bit then restarting the car it starts right up. Any ideas?
07-21-2018, 12:39 AM
#2
Racer
Thread Starter
Using the DIC to determine the state of health of the battery is an impossible task for several reasons. One is that the gauges are downstream of the ignition switch and the C5 ignition switch is well known for having pitted and burned contacts so the gauges typically report a voltage LESS than the actual voltage measured with a digital multi meter across the battery posts. Second the voltage seen with the key ON but engine off is the loaded battery voltage since there are many electrical circuits in the C5 that place an electrical load on the battery at that time. The voltage gauges were intended to help determine the state of health of the charging system and NOT the state of health of the battery. Unfortunately with the known ignition switch issues it typically reports an alternator output LOWER than the actual output. 
Many recent "hard start" threads on the forum the past few moths. Next time the engine is overnight cold, turn the key to ON (NOT START) and leave it there for about 10 seconds. Does the car start right up after the delay or does it still exhibit a hard start??? If it starts right up you have a fuel pressure leakage issue. Could be one or more bad (leaking) injectors or the fuel pressure check valve at the tank is leaning pressure.
Many recent "hard start" threads on the forum the past few moths. Next time the engine is overnight cold, turn the key to ON (NOT START) and leave it there for about 10 seconds. Does the car start right up after the delay or does it still exhibit a hard start??? If it starts right up you have a fuel pressure leakage issue. Could be one or more bad (leaking) injectors or the fuel pressure check valve at the tank is leaning pressure.
07-22-2018, 01:30 AM
#3
Racer
Thread Starter
07-22-2018, 05:52 PM
#4
Racer
Thread Starter
With the symptom being it only hard starts on cold (ie starts OK with warm engine) and apparently no loss of fuel pressure, the problem is most likely electrical/sensor related. Todays cars use all sorts of sensors to tell the PCM how to set fuel and spark. Likely one or more sensors are not telling the PCM the correct info and the fuel/spark are incorrectly set when the engine is cold. Temp sensor as well as cam and crank sensor and likely other sensor inputs are critical inputs to the PCM. Next time you have a cold start issue, once the engine is running, pull the codes WITH THE ENGINE RUNNING. If you are lucky a bad sensor may rear its head and set a code.
To pull codes with the engine running use the RESET button to clear any messages displayed in the DIC and then pull codes as normal.
You might also consider dong the ignition switch diagnostic testing in the following link:
diagnosis
http://forums.corvetteforum.com/1568186703-post64.html
Perhaps low voltage to one or more sensors is causing them to not report correctly.
Beyond that I have no other suggestions.............
To pull codes with the engine running use the RESET button to clear any messages displayed in the DIC and then pull codes as normal.
You might also consider dong the ignition switch diagnostic testing in the following link:
diagnosis
http://forums.corvetteforum.com/1568186703-post64.html
Perhaps low voltage to one or more sensors is causing them to not report correctly.
Beyond that I have no other suggestions.............
07-23-2018, 02:18 PM
#5
Tech Contributor
Member Since: Dec 1999
Location: Anthony TX
Posts: 32,736
Received 2,180 Likes
on
1,583 Posts
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Hmmmmm...
07-23-2018, 02:24 PM
#6
Racer
Thread Starter
07-23-2018, 03:53 PM
#8
Racer
Thread Starter
You need to have the battery checked!!! If you have a digital multi meter you can measure it as I described in my post #8 above.
With the messages that displayed on the DIC during your attempt to start the car there are certainly DTC's set if you pull the codes using the following procedure:
If you have never pulled codes on your C5 here is how:
https://youtu.be/SviRjIsy9G4
Post ALL the codes including the H or C or HC after each 5 character code. List the codes under the sensor they show with. ie 10 - PCM or 28 - TCS or 40 - BCM ..... etc .....
If any sensor(s) have NO COMM next to them post that also.
Many here can help you understand the meaning of the codes your car may have.
Pull the codes with the engine running. I explained how to do that above in post #6.
With the messages that displayed on the DIC during your attempt to start the car there are certainly DTC's set if you pull the codes using the following procedure:
If you have never pulled codes on your C5 here is how:
https://youtu.be/SviRjIsy9G4
Post ALL the codes including the H or C or HC after each 5 character code. List the codes under the sensor they show with. ie 10 - PCM or 28 - TCS or 40 - BCM ..... etc .....
If any sensor(s) have NO COMM next to them post that also.
Many here can help you understand the meaning of the codes your car may have.
Pull the codes with the engine running. I explained how to do that above in post #6.