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93 z28 won't start please help

Old 01-03-2015, 02:04 PM
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93 z28 won't start please help

Hi I need a little help I am stumped on what to do. Recently the car was running perfect. Then the other day I noticed it was leaking oil like crazy. I crawled under to find the oil pressure sender was cracked I replaced it and started it up, pulled out the drive way and around the block. Then it started chugging and was barely able to get it home. Now it just cranks and cranks and cranks but won't start. I made sure it had fuel and can here the fuel pump whine. I know it's get fuel to the rail by pressing the pressure valve. I am stumped any help would be amazing.
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Old 01-03-2015, 03:08 PM
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Re: 93 z28 won't start please help

Did you refill the oil before restarting it?

Did the leaking oil coat the O2 sensors? They can be contaminated by external material.

Have you scanned it for codes:

http://shbox.com/1/dlc2.jpg

You need to verify fuel pressure with pressure gauge. Simply depressing the pin in the Schrader valve does not prove the pump is producing adequate pressure.
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Old 01-04-2015, 12:05 AM
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Re: 93 z28 won't start please help

Yea I topped off the oil. The exhaust stayed pretty clear of the oil pretty much the only thing that got any I it was the underside of the floor board and the driveway. I know for sure it's kicking some codes not sure which ones thou cause the check engine light has been on since I put on the cold air and the exhaust from the cats back. Only thing is now I am kinda stuck with out it starting I can't get it to the autozone to check them and they want a ridiculous amont to rent the obd. Is there any other way to check them? I took the first spark plug out to see if it was wet from just cranking over and it was dey as a bone and fresh looking like the day I bought them. I will have to get a gauge tomorrow I just thought since gas was in there it was working never thought it wasn't enough thank you.
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Old 01-04-2015, 09:21 AM
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Re: 93 z28 won't start please help

Did you not look at the link I posted?

It tells you how to pull codes on a 93 using a paper clip.

HERE IT IS AGAIN

http://shbox.com/1/dlc2.jpg

And here's a list of the codes - note 93 codes are different than other years, and are indicated separately on the right side of the page, where different.

http://shbox.com/1/Dtcs.htm

When someone tries to help you, you have to read the response carefully, and follow the links.
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Old 01-04-2015, 11:56 AM
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Re: 93 z28 won't start please help

Ohhhhhhh wow I didn't even see the paper clip that is a really fancy trick I ran out and did it the light flashed 5 times x3 and 6 x3
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Old 01-04-2015, 01:05 PM
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Re: 93 z28 won't start please help

Go back and read the instructions for counting the pulses. All codes have two digits, not a single digit. The first digit flashes, there is a brief pause, then the second digit flashes. Then there is a long pause. Process repeats two more times.

Did you get code 12 first, which acknowledges the the PCM is in diagnostic mode?
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Old 01-04-2015, 03:57 PM
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Re: 93 z28 won't start please help

That makes so much more sense I got 15, 16, 22 and 26
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Old 01-04-2015, 05:18 PM
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Re: 93 z28 won't start please help

DTC 15 = coolant temp sensor, low temp indicated.

This is the coolant temp sensor in the water pump housing. Could be as simple as the wire being off the sensor.


DTC 16 = Loss of low resolution pulse from the optical cam position sensor in the Optispark distributor.

This is what is preventing the engine from starting, if the code is active (could be stored). ECM shuts down the fuel system.


DTC 22 = Low voltage on the throttle position sensor.

Easy to check with a volt meter.


DTC 26 = Quad driver module #1

You have a open or shorted circuit on one of these systems - AIR pump fuse, EGR vacuum solenoid; EVAP purge solenoid.


Clear the codes by pulling the ECM BAT fuse in the panel at the end of the dash for 30 seconds. Try and start it again. See if DTC 16 comes back. That will tell you if the Opti (or the Opti harness connector) is the problem.
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Old 01-04-2015, 07:06 PM
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Re: 93 z28 won't start please help

Ok I pulled the fuse and paper clip then gave a long 30 count and replaced the fuse then the car started but wouldn't idle unless was giving some throttle the service engine light came back on and the car sputtered dead. I checked the codes again and the same four popped up including dtc 16

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Old 01-05-2015, 07:51 AM
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Re: 93 z28 won't start please help

Are you sure they "cleared"?
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Old 01-05-2015, 04:40 PM
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Re: 93 z28 won't start please help

The 15 and 16 must be stored cause I pulled the fuse before I went to work I came back after work and reran the test and the other two didn't flash only 15 and 16
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Old 01-05-2015, 06:08 PM
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Re: 93 z28 won't start please help

You may need a new distributor. But first, check the coolant temp sensor to make sure the harness connector is plugged in. If it is, unplug it, turn the key to "run", and measure the voltage between the two wires in the connector - should be 5V. Then, harness off the sensor, read the resistance across the two pins on the sensor. Table of resistance vs. temperature is on shbox.com

Advise results of above tests.

Then check both ends of the short Opti harness for corroded connectors, damaged pins, or missing insulation on the wires.
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Old 01-06-2015, 10:04 PM
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Re: 93 z28 won't start please help

Ok so today I tested the temp sensor the connector had 5v but the sensor itself had like 3 ohms so I replaced the sensor. The car starts up and runs but something just didn't seem right still so I checked the codes the temp gauge was gone but still getting and egr valve one and tps so I trouble shot the tps like the website you sent said which by the way I absolutely love. I had power on gray wire and using the ground so know the power and ground were good then check volts on blue wire and had like 3 I belive but when throttle was applied it didn't raise so I figured something was up. It has a aftermarket holly throttle body from the previous owner. I unscrewed the tps and sure enough when they had put the tps on the throttle body they rounded off the Notchs on it so the when the throttle opened it never grabbed the tbs to turn it. I have to order a new one do you think this could be a big part of the problem
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Old 01-07-2015, 08:53 AM
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Re: 93 z28 won't start please help

A faulty coolant temp sensor can cause hard starts (extended cranking), rough idle and high fuel useage. But it shouldn't prevent the engine totally from starting. If it's causing a very rich condition that tends to flood the engine, put the accel pedal on the floor BEFORE you turn the key to "start", and hold the pedal on the floor until the engine starts. That puts the PCM in "clear flood" mode. A fault TPS reading prevents this though, because the PCM doesn't know the throttle is "wide open".
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