Intermittent Starting Problem!!!
11-24-2007, 06:29 PM
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Intermittent Starting Problem!!! Here's the deal.
I have a 1999 Camaro SS, with a ls-1 engine. The Car has had ZERO problems until now. It starts now only once in a while. The battery is fully charged. The starter is cranking the engine. I can hear the fuel pump prime when I turn the key to "on". It starts once in say..every 15 tries. Hot or cold does not seem to be an issue. when it does start, it starts like there was never any problem, and runs great. as soon as I stop the engine, same problem.
Things I have done to the engine recently:
run fuel system cleaner
remove and replace the intake manifold to replace the knock sensors. (prob. did not start till about a week after this)
spray throttle body cleaner thru the throttle body (when i did the knock sensors)
The computer is not popping any codes. I am hoping someone has had a problem like this , and can help me narrow down the cause.
I have a 1999 Camaro SS, with a ls-1 engine. The Car has had ZERO problems until now. It starts now only once in a while. The battery is fully charged. The starter is cranking the engine. I can hear the fuel pump prime when I turn the key to "on". It starts once in say..every 15 tries. Hot or cold does not seem to be an issue. when it does start, it starts like there was never any problem, and runs great. as soon as I stop the engine, same problem.
Things I have done to the engine recently:
run fuel system cleaner
remove and replace the intake manifold to replace the knock sensors. (prob. did not start till about a week after this)
spray throttle body cleaner thru the throttle body (when i did the knock sensors)
The computer is not popping any codes. I am hoping someone has had a problem like this , and can help me narrow down the cause.
11-24-2007, 10:26 PM
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alright man first i would make sure that you are actually getting fuel pressure,try changing your filter first,
then after that check the wiring to the ckp sensor and the cmp sensor, if you still find nothing check the pcm wiring if nothing really stick its head at you, check the passenger door module, sometime if these fail the engine will not start but i think this is a far shot, when these go out none of the acc work in the car,,
check all that stuff and see, also make sure that there isnt a loose connection at the ignition coils on each side of the valve cover, that should keep you busy,
honestly my money is on the ckp has failed, when these intermantely fail theyre are really hard to diagnose, unless you have a lab scope and get lucky enought to spot it acting up,
good luck and post what you find
then after that check the wiring to the ckp sensor and the cmp sensor, if you still find nothing check the pcm wiring if nothing really stick its head at you, check the passenger door module, sometime if these fail the engine will not start but i think this is a far shot, when these go out none of the acc work in the car,,
check all that stuff and see, also make sure that there isnt a loose connection at the ignition coils on each side of the valve cover, that should keep you busy,
honestly my money is on the ckp has failed, when these intermantely fail theyre are really hard to diagnose, unless you have a lab scope and get lucky enought to spot it acting up,
good luck and post what you find
11-24-2007, 11:17 PM
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Cam postion sensor determins injector pulse and wont cause a non-start. Most likely it's a crank sensor, If the starter is cranking but no spark then I would replace it. Also check for proper fuel pressure if you do have a spark.
11-24-2007, 11:24 PM
#6
I had the same exact problem on my 98 and i couldn't figure it out. I finally took it to an electrician and he found it in about 20 minutes. it was some bad wiring and was not getting sufficient power to the fuel pump. he fixed it for $25.
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11-25-2007, 12:55 PM
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I know how a injector works but did you know if the cam sensor goes bad the the ref voltage will make the pcm throw a code? He said there is no codes i have seen crank sensors get dirty and now get a proper magnetic pick up but hey your the ase gold master tech here so why argue with you right?
11-25-2007, 12:59 PM
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Here's the deal.
I have a 1999 Camaro SS, with a ls-1 engine. The Car has had ZERO problems until now. It starts now only once in a while. The battery is fully charged. The starter is cranking the engine. I can hear the fuel pump prime when I turn the key to "on". It starts once in say..every 15 tries. Hot or cold does not seem to be an issue. when it does start, it starts like there was never any problem, and runs great. as soon as I stop the engine, same problem.
Things I have done to the engine recently:
run fuel system cleaner
remove and replace the intake manifold to replace the knock sensors. (prob. did not start till about a week after this)
spray throttle body cleaner thru the throttle body (when i did the knock sensors)
The computer is not popping any codes. I am hoping someone has had a problem like this , and can help me narrow down the cause.
I have a 1999 Camaro SS, with a ls-1 engine. The Car has had ZERO problems until now. It starts now only once in a while. The battery is fully charged. The starter is cranking the engine. I can hear the fuel pump prime when I turn the key to "on". It starts once in say..every 15 tries. Hot or cold does not seem to be an issue. when it does start, it starts like there was never any problem, and runs great. as soon as I stop the engine, same problem.
Things I have done to the engine recently:
run fuel system cleaner
remove and replace the intake manifold to replace the knock sensors. (prob. did not start till about a week after this)
spray throttle body cleaner thru the throttle body (when i did the knock sensors)
The computer is not popping any codes. I am hoping someone has had a problem like this , and can help me narrow down the cause.
if you take it to a shop they will charge about $60 for diagnostics and will carry the fee over toward the repair if you get it done there
11-25-2007, 01:02 PM
#12
So you've never seen a sensor fail with out throwing a code. If you read the first post you would see he said it was a intermitent problem. I mearly stated the two most obvious sensors to look at. But you know best because no one else but you can fix a car. Better ask for that raise!
11-25-2007, 01:08 PM
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So you've never seen a sensor fail with out throwing a code. If you read the first post you would see he said it was a intermitent problem. I mearly stated the two most obvious sensors to look at. But you know best because no one else but you can fix a car. Better ask for that raise!
11-25-2007, 01:34 PM
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So you've never seen a sensor fail with out throwing a code. If you read the first post you would see he said it was a intermitent problem. I mearly stated the two most obvious sensors to look at. But you know best because no one else but you can fix a car. Better ask for that raise!
But i shouldn't say a cam sensor wont cause a non start because it can but he said there was no codes so first thing i was thinking was spark, fuel and air (vacumm).
11-25-2007, 01:42 PM
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i too have diagnosed a failed ckp sensor with no trouble codes,
sometimes they collect too much metal fuzz and the signal can be distorted,
this also sounds like a long shot but try disconnecting the alternator connector, sometimes an alternator can emit a rf signal which interefears with many sensors,
sometimes they collect too much metal fuzz and the signal can be distorted,
this also sounds like a long shot but try disconnecting the alternator connector, sometimes an alternator can emit a rf signal which interefears with many sensors,
11-25-2007, 01:46 PM
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also the way i understand it,
if you are driving and your cmp sensor fails or the pcm loses connection with it, you car can still run, you pcm just uses the ckp, but as soon as you turn your car off it will not start again.
so with that said i to agree with ls1z that i would first check the cmp sensor and or wiring and ckp sensor and or wiring, i think you will find your problem there,
luke
if you are driving and your cmp sensor fails or the pcm loses connection with it, you car can still run, you pcm just uses the ckp, but as soon as you turn your car off it will not start again.
so with that said i to agree with ls1z that i would first check the cmp sensor and or wiring and ckp sensor and or wiring, i think you will find your problem there,
luke
11-25-2007, 02:16 PM
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Before we get all technical and start getting into sensors let check fuel pressure, and spark. Let not get ahead of things here guys, he did say it starts sometimes but no DTC. if everything checks out fine let go into the sensors if the crank/cam sensor where to loose connection with the pcm the pcm would throw a code when it dosn't get a ref voltage from it. but you never know sometime **** happens. it dosn't have to be a cam or crank sensor gone bad, it could be voltage to the injectors/coil packs as well. Injectors and the coil packs have fuses to you know, Before you start sending him to go buy expensive sensors he need to determine the cause of it. Since ive seen non blown fuses do funny things. It can even be VATS because the key has a resistance that you BCM uses to know the car is not being stolen.
Last edited by XpEdItIoUs; 11-25-2007 at 02:46 PM.
