Good luck. A lot of the fsm diagnostics start with "connect the tech 2". There is enough info in the fsm to help even if you don't have a scanner.
Btw...what did you do to get it started after replacing the harness??

 

I did the same thing I always do, I wiggled and jiggled wires. Sometimes it works, other times nothing changes. No specific area of jiggling is a common factor.
Sometimes the area around the ECM, sometimes around the coil, even once testing the fuse box with a test light caused it to start up. Sometimes I can wiggle every wire on the car and it won't start no matter what I do. Other times, it will start just by waiting a few minutes.

When I first bought the car, I could drive it about 10 miles, then it would die, but start back up. It got progressively worse, until it reached the point it is now.

Sara Lou

 

Magazine!

 

Since I've owned my 93 LT-1 I've had two 2 parts of the car cause a start, no start. One was the ECM, but it was heat related. After troubleshooting I finally decided to take it out of the car and inspect the internals. Now i was doing this in the summer in the AC and didn't find anything out of the ordinary. When I reinstalled it in the car it would start sometimes and then shutoff. I finally saw a recommendation to tap on the ECM and long behold the car died, so I had the ECM repaired.

The second part was the starter. I found out when I removed it that the internal copper contacts were worn out and sometimes the plunger would engage and sometimes it wouldn't. It cost me around $40.00 to repair. The repair kit comes with new contacts and a plunger.

Also, make sure your troubleshooting with a fully charged battery that passes a load test. It's a pain in the *** to take off parts, but most can be tested at the auto parts store if you don't have the right tools. If it were me and the starter hasn't been checked I would look there. Especially if everything else appears fine.

Just something to think about. Good luck!

 

Seems to be more to do with time than jiggling wires. But you were able to make it shut down by jiggling wires. I wonder if you can recreate that? If so, it can possibly lead you to a bad connection.

 

Even the time factor is not consistent, sometimes I can get it to start within a few minutes, other times, I can mess with it for 3 days or more without it starting.

I doubt the starter for the simple fact of it will crank till the battery dies, whether it starts or not, I have no problem cranking the motor.

Sincere apologies, my bad!! , in defense I was p*ssed at the time I posted that!!

I'm 90% convinced the ecm is the main culprit, i'm guessing the battery also isn't helping matters, and I really need to set aside time to check all the grounds.
Hopefully, winter is working its way outta here, and warmer weather is on the horizon. Then I can spend some serious time working on the vette.

Sara Lou

 

Only 90% this time? jk It has gotta really suck to have a car that you can't drive. Good luck and keep us updated.

 

Is this car a stick or an automatic ? My ZR1 constantly had no starts until I jumpered out the clutch innerlock switch. Its a fat purple wire behind the clutch pedal. I used to jump start it by rolling and popping the clutch so I knew that coil and ECM were good.

My 2 cents.

 

Nice! Now thats thinking outside the box. A bad neutral safety switch will do it too. At least worth checking.

For what its worth. My moneys on the ECM....h

 

Until I can get my hands on a Z06 C5, i've gotten lazy in my old age. Its auto...

I dropped it to 90% because i'm not 100% sure the opti isn't bad, plus I haven't checked the grounds yet either.

Sara Lou

 

The weather is supposed to be great this weekend. Maybe you will finally break the code on this one.

 

Finally managed to get my hands on book 2 of the FSM, so I did a little tinkering this week.

I started probing the ECM to Opti harness.
Low resolution wire= 5 volts
High resolution wire= 5 volts
Ignition wire= illuminates test light

Now the ground.
ignition off= 0 resistance
ignition on= I get a reading of 153. Is this normal?

I can't do much investigation just yet, due to the storms that went through here last week:



As you can see, I don't have much use of the workshop just now.

Sara Lou

 

The saga continues:

Well, I got the sheet metal back on the workshop (still gotta seal the holes left by the old screws, but at least I have some cover now).

Had another play around with the vette today. Started up, ran couple of seconds, then died. Got it started again, ran a little longer this time. It's now back to the same thing it was when I first got the car, just before it dies, SES light comes on with code 28, I then flash codes and it will start again.

I know the code 28 is quad drivers and shouldn't have any affect on it 'dying', but it seems soon as that code causes the SES, it kills the car. I'm wondering if the computer is dying and the only code it throws is 28 as it fails? (I also have a code 64, oxygen sensor, but that definitely wouldn't cause a no-start).

Reading all the previous owners posts here, he replaced both the opti and computer more than once?.

I'm at the point where i'm ready to just replace the ECM, but I don't like the idea of spending $350+ on a replacement if it isn't going to solve anything.

Anyone have any good tips for getting at the ground locations?, obviously I can't run it up on ramps (doesn't stay running long enough), ohh and car has long tube headers. Any good spots to jack the whole front end up?, I don't like the idea of getting it that high one side at a time, for fear of twisting the frame.

Sara Lou

 

Well I went back to the workshop and jacked the car little by little, one side at a time, so now its on ramps.

What I found was disturbing.....

This pretty little rats nest was carefully 'stuffed' in front of the air filter box:



Anyone care to guess where it went?....



Which is feeding power to.......



Why do people do things like this??. Kinda explains why I'm getting codes for O2 sensors.

I also tried the noid light test (dont have a noid light, so just used a test light). Strange results?, I have steady light on BOTH wires when grounded?. Tried two different injectors, same results.

Sara Lou

 

Sara, You will see voltage on both pins of the injector connectors because the ECM is sending a ground pulse to activate the solenoid inside the injector body. With the igntion ON, you SHOULD see 12V on
both sides of the injector coil/solenoid (this tells you that the injector is OK electrically). The ground pulse only appears during cranking or running and you should be able to see that with a Noid or a 12V LED if you want to make your own. (+) side of LED to 12V source and the (-) side to the pulsed side of the injector connector.

Mick

 

Ahhh, that explains that one then. Thanks Mick.

Sara Lou

 

I don't know about '93 Vettes, but I had a '90 Pontiac that gave a quad driver code when the connector to the Evap canister purge valve was unplugged (showing OPEN circuit to the PCM), so I am inclined to think "Yes". Further speculation, if the Ignition Control Module is switched by a "quad driver", then a intermittent open circuit on the GROUND wire on the ICM or a intermittent open circuit on the line from the PCM to the ICM could cause a code for bad quad driver, and the engine would quit. First thing I would check would be the ground wire on the ICM. I'd even try back probing the connector at the ICM and establishing a separate ground to see if the problem goes away.

 

Code '28' is quad drivers that control fan and a/c relays. I don't see what affect either would have on ignition spark.


I tried the noid light test again, no flashing light while cranking....

Sara Lou

 

WOW, Doesn't that bring us all the way back to missing voltage or pulses from the Opti. No pulses, no injector action from the ECU.
I think your OPti harness and surrounding wires need more attention.

Mick

PS The alternator has nothing to do with this no-start condition. You can evaluate it later, once the engine runs long enough
for the alternator to produce charging current.

 

To me if the fuel injectors are not pulsing...then its the ECM and not the Opti.

Sara....have you replaced the alternator yet? The ECMs in these cars need to have the proper voltage and even with a good battery, the alternator output must be good or the ECM has a tendency to lose its mind. Even a low battery will affect the ECM operation.

After checking/replacing the alternator, then try the "beating on the ECM" idea. All it takes is one cracked solder joint or crack in the circuit board to cause an operation problem.

Keep after it.