Forum,

I am experiencing an occasional problem starting up the Z. Upon the turn of the ignition, it will fire up and then immediately dies out, and will eventually fire up on the second or third attempt. However today, it took about 5 tries before it would start up.

My Z is bone stock with no engine mods. The only thing done to it recently has been a new set of plugs.

Any input/assist would surely be appreciated.

 

I went through a similar problem and it ended up being the fuse box!

The relay contacts for the fuel pump were stressed.

I found this out when I pulled the relay and it came out REAL EASY.

NOT GOOD!

I "shimmed" the relay blades with a coating of silver solder.

Works now.

 

That makes sense as the symptom is almost like a lack of fuel.

A little more help on the location of fuse for the Fuel Pump please? I am without a manual.

 

So after work, I popped the hood on the Z and found the Fuse box. Looking inside, I found a 20A fuse (#15) and a rectangular Relay (#35). The fuse at 13 didn't look damaged but I replaced it, but 35 was on there pretty tight and so I just left it alone. Am I on the right track?

 

Sounds like you found it (location of fuses and relays).

Intermittent problems are the PITS to find.

You might wiggle these items in the fuse block (car running) and see if the relay "chatters" as mine did, due to the connection.

I helped a friend of mine (C5 Z06) with an intermittent starting problem and it ended up being the fuel pump.

 

Since you changed your spark plugs, re-check to make sure there is no play in any of them. I don't think this is your issue, but they used to back out on me if not tightened all the way.

Second, check the cables on the battery. Mine became loose once and it would take time to start. My clock would reset too which is how I found that they was a weak connection somewhere. Then it came down to one of the cables not being tightened to the battery. It had some play in it (you could grab and wiggle it around).

 

Thanks! I'll check the plugs to make sure they're all properly tightened. As for the battery cables, the car cranks and starts up everytime, but immediately dies out so that shouldn't be the potential culprit could it?

 

Well you aren't that far away.

If it gets to where your stuck, I might be able to give ya a hand.

 

Your battery connection is fine, otherwise you would not be able to turn the motor and once started your altenator would take over from there. Do you have any drivability issues? And what plugs did you put in? did this all start after you put the plugs in? I ask because you can buy plugs at different heat ranges. These heat ranges are for "cleaning" of the electrode so that hydrocarbons do not build but burn off. Check all the plugs and see if there is build-up. If so, clean with parts cleaner and reinstall. See if that fixes ur problem. If it does, just buy GM oem plugs, your only running a stock motor.

Tell us as much as you can...

 

I believe the new plugs are NGK Iridiums which came uninstalled when I bought the Z and I installed them along with new OEM wires. I have experienced no drivability issues (no sputtering, no misfires...) with the new plugs, just the intermittent start-up problem at hand. Hope to take a look at the plugs this weekend and we'll go from there. Thanks again for the input!


Thanks for the offer of assistance. I may take you up on it if I get stuck.

 

Your welcome.

Like I said, intermittents are the PITTS to find.

 

Well...the issue came up again after I changed the fuse. I have not tinkered with the Fuel Pump Relay at the fuse box as it was not easily removed.

I'll have to pull the plugs to see if they are fouled in some manner.

Hate these Gremlins.

 

I don't think you have a plug issue.

It might be the keyswitch.

 

Is there a code set?

I think you are having a VATS issue. If the car doesn't have a lot of miles on it you might just benefit from removing the ignition switch and cleaning the metal contacts. There is a thread by Bill Curlee that details this really well. There are other issues that go along with this whole problem but that one sounds like yours to me.

The last thing you want to do is start throwing money at it: key, ignition switch, BCM, SCM.....and the list grows.

 

Wow the first post with good advice.....

ANYTIME you have an issue, check your codes 1st.

I'm amazed at how many people with C5s waste hours of their time and make posts asking for advice without performing a simple diagnostic check. Learn how to check your codes, it should become 2nd nature. Note the codes and clear them and see if any come back. This should at least give you a starting point to fixing your problem.

Sorry for my rant, but I've owned my C5 Z06 for 7 years and I've been on the forums for even longer. I'm amazed at how many people don't realize the network of computers in a C5 Corvette will write errors to a log file that you display as DIC codes TO HELP YOU. Don't ignore this feature of your car...please

 

Well...I took the Z out to stretch its legs after dinner tonight and to my limited knowledge, I also don't think any issues are spark plug related as it is running as smooth and responsive as it can be from a standing start to freeway acceleration.

I'll have to take up the advise and may be dig further into the ignition switch as recommended.

Thanks all. I'll post some updates soon.

 

So I took the advise and learned how to use the on-board diagnostics and pulled the following codes:

TCS - C1276H
RDCM - B2265H

I don't think either one is related to my current issue. Ideas?

 

C1276 could give you a clue:

The EBCM and the PCM simultaneously control the traction control. The PCM reduces the amount of torque supplied to the drive wheels by retarding spark timing and selectively turning off fuel injectors. The EBCM actively applies the brakes to the front wheels in order to reduce torque.

The EBCM sends a requested torque message via a pulse width modulated (PWM) signal to the PCM. The duty cycle of the signal is used to determine how much engine torque the EBCM is requesting the PCM to deliver. Normal values are between 10 and 90 percent duty cycle. The signal should be at 90 percent when traction control is not active and at lower values during traction control activations. The PCM supplies a pull up voltage of 5 volts that the EBCM switches to ground to create the signal.

The PCM sends a delivered torque message via a pulse width modulated (PWM) signal to the EBCM. The duty cycle of the signal is used to determine how much engine torque the PCM is delivering. Normal values are between 10 and 90 percent duty cycle. The signal should be at low values (around 10 percent) at idle and higher values under driving conditions. The EBCM supplies a pull up voltage of 12 volts that the PCM switches to ground to create the signal.

When certain PCM DTCs are set, the PCM will not be able to perform the torque reduction portion of traction control. A serial data message is sent to the EBCM indicating that traction control is not allowed.

Conditions for Running the DTC
The engine is running.

Conditions for Setting the DTC
C1276
One of the following conditions exists:

The EBCM detects that delivered torque signal is out of the valid range.
The EBCM does not receive the delivered torque signal

The following conditions can cause this concern:

An open in the delivered torque circuit.
An short to ground or voltage in the delivered torque circuit.
A wiring problem, terminal corrosion, or poor connection in the delivered torque circuit.
A communication frequency problem.
A communication duty cycle problem.
The EBCM is not receiving information from the PCM.
Loose or corroded EBCM ground or PCM ground.



Since this error "could" be caused by a bad/loose ground (PCM/EBCM) maybe this bad/loose ground point has gotten worse and is now causing your starting issue.

Also, clear the codes you had and then see if they come back. If they don't come back then probably just a communication "hiccup".

Another odd thing you can try is disconnect the battery for 15 minutes at least. Then connect battery and leave the car alone for at least 15 minutes, let all the systems come up in order. If you had a dead battery recently that could be your issue. The computer systems have to come up in order on the network, otherwise your car can do all kinds of goofy things until the systems come up properly.

I want to be clear that I'm not saying it isn't your ignition switch, or what others have mentioned, it's just smart to check your codes first because it could tell you exactly what your issue is or give you some clues.

 

http://forums.corvetteforum.com/c5-t...tion-long.html

A good post on the electrical system and ground points.


http://forums.corvetteforum.com/c5-t...-and-dies.html

similar situation??

 

Wow...all this knowledge and on the 4th of July at that!! Thanks brother!

I acquired the Z in March, and the previous owner did mention that he hadn't been driving it enough and the battery had DIED so he purchased a new battery for it.



Another good pointer. Thanks!!!