Intermittent no start condition

[Rich Biebel]

Originally Posted by ss3011

Thanks for the info John. Now we know that none of the trigger electronics in the Opti-Spark have anything to do with your no start condition. It is so hard to track down intermittent problems. Since you have spark it is a good bet that you have a connection or wiring problem. Usually ECU's either work or they don't. Have you tried disconnecting the main injector connector and reconnecting it ? Most all the terminals are crimp connectors. If you know which wires are the power leads, then when you have a no-start condition leave the power on and probe to see if indeed you have the 12v power to the injectors. The ECU provides the ground to pulse the injectors. If you don't have it set up for sequential , which I don't think you do, because the Opti-Spark trigger is not hooked up. Then your system fires 4 injectors at once. Everytime the ECU sees 4 pulses from the crank trigger it fires a set of 4 injectors, usually bank to bank. It doesn't know when, since it has no particular cylinder reference, just every 4 pulses. Your ignition works, so the ECU is getting the pulses. If the injectors aren't firing then check the simple things first, like the connector connections, 12V supply to the harness, etc. You will figure it out, that DFI system is very reliable.

I agree 100% with this post.....and this advice is spot on....

[John Nechiporchik]

SS3011 and Rich,
This morning I read your post again and went back to the drawing board. I have the wire pin out list and started looking for the power feed circuits(+12v) to the ECU. I found a power feed that had an in-line fuse in a Packard fuse holder with a cover on it. I looked at this previously and thought it was a connector....not a fuse. Well, I popped the cover and found a blown 30 amp fuse. Replaced the fuse, car fired right up. I started it 7 times and each time it fired up.
Recall this started as an intermittent problem, then a full blown no start. So, the fuse got the car running again. I'm hopeful that running the ground back to the negative battery lug solves the intermittent issue. I will continue to start it randomly throughout the day and validate that the problem is solved.
I will also replace the coil as the MSD 8261 seems to have a history of problems.
I hope this is the last I need to post on this issue.
I want to say "Thank You" to all of the help you guys have given me as we walked through this thing.
I learned more about this electronic fuel injection system in a week then I thought I would ever learn!!!

[Rich Biebel]

Great news John and I was pretty sure you would find something if you dug into the wire connections.

I work on electrical equipment everyday.....Nothing worse than an intermittent problem but I get them all the time...

We have a little Joke saying at work that covers this....

A good visual inspection will often reveal the problem...

I work on Miller Welders and that saying comes from them and has always been true...

With all the electronics these days that is not so true anymore but you have to start with the basics....

I am glad something I wrote may have helped you

I kind of wish I had my Firebird back....I really loved the wheelies.....LOL

[Bobby DiDomenico]

Originally Posted by John Nechiporchik

SS3011 and Rich,
This morning I read your post again and went back to the drawing board. I have the wire pin out list and started looking for the power feed circuits(+12v) to the ECU. I found a power feed that had an in-line fuse in a Packard fuse holder with a cover on it. I looked at this previously and thought it was a connector....not a fuse. Well, I popped the cover and found a blown 30 amp fuse. Replaced the fuse, car fired right up. I started it 7 times and each time it fired up.
Recall this started as an intermittent problem, then a full blown no start. So, the fuse got the car running again. I'm hopeful that running the ground back to the negative battery lug solves the intermittent issue. I will continue to start it randomly throughout the day and validate that the problem is solved.
I will also replace the coil as the MSD 8261 seems to have a history of problems.
I hope this is the last I need to post on this issue.
I want to say "Thank You" to all of the help you guys have given me as we walked through this thing.
I learned more about this electronic fuel injection system in a week then I thought I would ever learn!!!

John,
Been following this with some interest after talking with a guy at a cruise night near me who installed a tuned port Chevy into his Avanti and he mentioned some issues he was having. That 30 amp fuse is pretty big, maybe see if you have a loose connection somewhere which popped it when contact was re-established. A 30 amp breaker would reset but you'd need to have some type of indication it tripped, such as a light which illuminates when that circuit becomes open so you would be aware of potential issues.

[John Nechiporchik]

Bobby, After I got the car running, I tried to carefully reconstruct the test process that I followed and determined the following: The intermittent condition turned into a 100% no start condition as I was testing the various components. When I got to testing the injector connector, the homemade noid light ( a line lock light with two 6" leads with the correct terminals) .......I plugged one lead into the connector and the second lead momentarily touched the intake, resulting in a quick spark. I subsequently realized that this spark was the indicator that the fuse blew.
So, I'm pretty confident that I have isolated the root cause of the blown fuse.
Also, I believe isolating the ECU ground circuit from the stud with 6 ground leads stacke up (ran ground to - battery lug) took care of the intermittent condition. This was based on advice from an Accell service rep.
Thanks for your input.

[FED 387]

jon --sent u a PM--FED 387

[John Nechiporchik]

Got it.