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Old 11-11-2013, 11:18 PM   #1
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95 Z28 won't start

Hey guys I have a 95 z28 that was having problems, at first we thought it was the fuel pump. It was having really bad crank times, would take like 5-10 seconds to start sometimes then it would almost stall going into first gear on the streets, also smoke would come from the exhaust on start ups. There was also a really bad gas smell coming from the drivers side. It ended up stopping at an auto zone and I couldn't start it, it would crank fine though but it sounded like there was no gas which there was. The next day I had it towed and I left the key in the ignition like the guy told me. When we got home it wouldn't even crank. Now we replaced the starter, fuel pump, and the optispark wire harness and it'll crank once but it'll just crank once over and over we think its the optispark now since we checked it wasn't getting any volts. Any other problems y'all would think it is? Also can someone point me in the right direction on how to change the optispark, I found a thread once but then lost it. Thanks.

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Old 11-12-2013, 09:25 AM   #2
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Re: 95 Z28 won't start

Description of "cranking" is unclear. "Crank" to many people means the starter actually turning the engine. You indicate:

Quote:
it'll crank once but it'll just crank once over and over
To clarify, do you mean the starter turns the engine only once, and then stops working? Or do you mean when the starter is turning the engine, it attemps to start once?

Scan if for codes. A faulty Opti would set codes that will show up even when you are attempting to start the engine.

Then you indicate:

Quote:
we think its the optispark now since we checked it wasn't getting any volts.
Do you mean the PCM was not supplying 12V to the Opti on the red wire (terminal C), or do you mean there was no voltage on the signal wires from the Opti (red/black - terminal A - low resolution pulse; purple/white - terminal B - high resolution signal)?

Extended start experienced earlier could be due to a faulty check valve in the fuel pump, leaking injectors, or a faulty fuel pressure regulator. Did you check the fuel pressure? What was the psi as the pump primied, and how fast did the pressure drop off when the pump shut off?

Could also be a faulty coolant temp sensor in the water pump housing. If that tells the PCM the engine is cold, the PCM richens the mixture for a very cold start, and it would explain the extended start, near stall, and smoke coming from the exhaust. A faulty coolant temp sensor may set a trouble code (total failure), or it may not (incorrect resistance, producing incorrect temp readings).
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Old 11-14-2013, 07:04 PM   #3
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Re: 95 Z28 won't start

The starter turns the engine once but it goes over and over..I don't really know how to explain it. I'm not that experienced with cars since I work with my dad on my cars and he's the one that knows everything I've just been working with him for about a year. Also I went to autozone and I couldn't scan since they said I needes the check engine light. The terminal was B that had 0 voltage. I'm going to check out the coolant temp sensor tomorrow. Also new update: I drained the oil today and there was fuel everywhere..any ideas? My dad says it could be the fuel pump was running too much pressure? There was also fuel in a spark plug I pulled.

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Old 11-14-2013, 07:28 PM   #4
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Re: 95 Z28 won't start

The SES light does not have to be on in order to scan the PCM. Usual problem when they see a 95 is they see the 16-pin ALDL connector and assume you have an OBD-2 PCM. They hook up an OBD-2 scanner and get "cannot connect". You have an OBD-1 PCM and they need to use an OBD-1 scanner with the correct 12-pin to 16-pin adapter plug. Many auto parts stores won't even scan OBD-2.

Gas in the oil is a bad sign. It may be a damaged diaphragm in the fuel pressure regulator. That would pour fuel into the intake manifold via the fuel pressure regulator vacuum compensation line. Check that vacuum line for wet fuel.

Other things that could cause it to run rich enough to dilute the oil with fuel include:
-faulty coolant temp sensor
-leaking injector(s)
-excessive fuel pressure
-faulty O2 sensors.
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Old 11-14-2013, 07:28 PM
 
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