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Thread: 81 Won't Start

  1. #1
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    Default 81 Won't Start

    Hello,

    I'm a first time owner of a 1981 corvette with an automatic transmission. I shorted/ grounded the starter/ solenoid while changing the spark plugs which caused the car to have absolutely nothing when I turned the key. I'm not a mechanic but have always tried fixing things myself before paying someone else. I've been troubleshooting this voltage/ wiring issue on my small amount of spare time for the past 4-6 weeks. It appears that everything is original on the car. Not to sound like I'm throwing parts at the issue BUT I decided to replaced the starter, solenoid, ignition switch, dimmer switch, fuse links, battery, alternator, alarm relay and the negative cable from the battery to the frame (which brought the car back to life) along the way for piece of mind later. I did'n't replace the ground cable above the starter because it checked good. Ok, here's where I'm at: I don't have any voltage on the PURPLE wire entering the starter extension harness that feeds the solenoid. I think the issue is between what I think is the starter relay under the ashtray, the neutral safety switch or the relay under the arm rest?? All test are with the ignition in the ON position. With all items plugged in and in park I have 12+ volts on the PINK & SOLID PURPLE wires on the NSS. In reverse I have 12v on the GREEN. I didn't have anything on the PURPLE/ WHITE wire but when I pressed on it the relay under the arm rest clicks. Also, when I turn the key on, the relay in the arm rest clicks? I've traced the wires between the items and they appear to be fine? I need help with testing the NSS and what I should be seeing on the wires? When I unplug the Alarm relay, I don't have any voltage on the pins feeding it? When I unplug what I think is the starter relay, I have 12V on one of the pins feeding it? Am I on the right track? Any help appreciated.

    Sorry so long, Thanks in advance

  2. #2
    Administrator Tom Bryant's Avatar
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    Are you sure you didn't fry the ECM? Are you getting codes?

    Tom
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry
    1959 Chevrolet Corvette 1981 Chevrolet Corvette , 350 L81 automatic Frost Beige

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    Tom,

    I don't know if I fried the ECM? I took it out a couple weeks ago while tracking a short/ ground. I didn't notice anything obvious and after I found the trouble, I just put it back in. How do I test it? I'm clueless about if I'm getting codes... I read something a few weeks ago on how to check lights blinking but I didn't have any power at that time.

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    I read how to check the codes and I got code 23- Mix control solenoid (from memory)?? Not sure what or where that is? Will it cause a no start?

  5. #5
    Administrator Tom Bryant's Avatar
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    The code 23 is a Mixture control solenoid thing and I can't see how that would keep the engine from turning with the starter. It may be pointing to other drivability issues though. The Mixture Control solenoid is internal in the carb. The M/C connector is on the right front top of the carb. Check to be sure it is plugged it tightly. If it's OK remove voltage from the circuit to clear codes. Do this by either removing the ECM fuse or disconnect the battery ground for a minute or so. Then reconnect. Check for codes again. If no code 23 circuit is OK.

    If code is still there unplug the lead. Then turn ignition switch on (engine stopped) and check voltage at the M/C lead terminals. If under 10 volts there is a break in the system. If over 10 volts check voltage at ECM terminal 18. If under 10volts there is a open in the sol/ecm wire. If over 10volts check resistance through the M/C sol. Check at the sol terminals at the connector on the carb top. If under 10 ohms the manual says to replace the solenoid and the ECM. If over 10 ohms you have a faulty ECM connection or ECM.

    So worst case is that code 23 is telling you that you have a bad ECM and possibly a bad M/C solenoid. I still don't see how this would prevent the starter from running. Might prevent the engine from starting but it should still turn with the starter. I'll post the flow chart and the text from the service manual relating to no cranking issues. From what you have replaced so far I'd lean toward the relay or the purple wire (less likely).
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry
    1959 Chevrolet Corvette 1981 Chevrolet Corvette , 350 L81 automatic Frost Beige

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    Administrator Tom Bryant's Avatar
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    Scans of manual.
    Attached Thumbnails Attached Thumbnails 81-corvette-shop-man-starter-1-jpg   81-corvette-shop-man-starter-2-jpg  
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry
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    1959 Chevrolet Corvette 1981 Chevrolet Corvette , 350 L81 automatic Frost Beige

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    Tom, I'll study the information and get on it in the morning. I appreciate your insight. Thanks
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    Hello Tom,

    I figured out that I created several issues but finally got the Vette started. I grounded the starter solenoid hot wire to the block when I replaced it which put me right back where I started and also fried the neutral safety switch when I turned the key with one of the relays unplugged! Now the car starts but runs horrible. It idles high and shuts off unless I rev it at about 2000rpm. It idled rough on a cold start before all of this but would stay started and drive OK. I checked the codes and got the 23-Mixture Control Solenoid Circuit and 44-Oxygen Sensor Lean. I was told that a carburetor rebuild would fix this? Any suggestions ?

  9. #9
    Administrator Tom Bryant's Avatar
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    If the m/c sol is causing a lean mixture that would explain the o2 lean code. I suggest that before you throw any money at that carb do the tests I outlined in post 5 of this thread. Do this to see if you can isolate the problem to the m/c sol or wiring/connector. The first thing here is to remove the ECM fuse or disconnect the battery ground cable for 5 to 10 minutes. This erases the codes and also erases the ECM memory. Then reconnect the battery or reinstall the ECM fuse, start the car and go for a drive. Now the ECM has forgotten all of the settings it has remembered that were adjustments to a bad running situation and will start to learn fresh settings. Sometimes this will clear up a rough running situation. I used to do this plus add some fuel system cleaner like Lucas or Sea Foam every spring when I got our 81 out and it did smooth out the engine. If the codes set again and it still runs rough then do the tests I outlined.

    Tom
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry
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    1959 Chevrolet Corvette 1981 Chevrolet Corvette , 350 L81 automatic Frost Beige

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    Hello,

    I finally had time to troubleshoot. I disconnected the power and rechecked the spark plug wires and connections to the distributor. I had 2 wires crossed! I also went through and looked at everything I had disconnected during this whole process and all seems to be good. I reconnected the power and if I pump the gas once, it fires right up. However, I have to keep giving it gas to keep it running. I forced it around the block and checked the codes and now I get code #12. (which if I remember correctly is good?) I changed the fuel filter. With one pump of the gas, it idles high and after that fuel burns off, it shuts off. Fuel pump, maybe?

    Your thoughts are respected and appreciated
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  11. #11
    Administrator Tom Bryant's Avatar
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    Code 12 is "no reference pulses to ECM" This code is not stored in memory and will only flash while the fault is present. Check again your 4 post terminal distributor connector. Check closely that the terminal contact surfaces are clean and that they make contact when plugged in. Also recheck your ECM plug terminal 10. Even the slightest amount of crud or tarnish on these terminals can mess up the signals.

    Connect a voltmeter to the terminal 10 and to ground. With the engine idling check voltage and then check again at part throttle. If voltage increases you could still have a faulty ECM connection at either the ECM or the distributor or the ECM could be bad. If voltage doesn't increase at part throttle you could have a faulty distributor module. This is a common problem with HEI distributors. If you replace the distributor module get a good brand name replacement and not a cheap Chinese copy. They often fail quickly if they run at all.

    It could be a break in the wire from the distributor to the ECM also but I think you said you checked your wires before. I don't suspect the fuel pump because a weak pump would supply some gas and it would idle but starve at higher rpm.

    Tom
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry
    1959 Chevrolet Corvette 1981 Chevrolet Corvette , 350 L81 automatic Frost Beige

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