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16 years of no trouble, won't start, ideas please.
Problem. Will not start it acts as if it wants too. I ran it for about 30 minutes (no problems) parked it and got up the next morning to use it and that's when the problem began.
What I have. 1972 Chevy 400 with 1993 lt1 electronics and ltcc controlling the motor. The opti is mounted on a distributor on the back of the motor.
Troubleshooting . Fuel pressure 44 psi, spark from all eight coils.
Ltcc is telling me two and four blinks. Key on green then red flash when cranking the motor the green light is on. (I read up on it and talked to Bob b. Briefly. He said opti.)
question? . I have 2 other opti modules that I tried with the same results. Is it possible,? I guess it could be, 1 being a used Mitsubishi and the other Aip sensor(don't own a o scope to rule it out).
I just read through the opti sticky and will double check the wiring and voltages when I get home. Tomorrow from the Fire Dept.
Any other advise on what I may have missed?
I did order another opti sensor and the harness because that one is original. I have spent 10 + hours on this.
Re: 16 years of no trouble, won't start, ideas please.
One last thought that I forgot to mention, after reading the codes from the Ltcc and seeing2 blinks and 4 blinks which says check the white wire I redid the connection and still the same problem of not starting. no trouble codes in the 93 computer.
And an off-the-wall-comment..... are you sure the Opti shutter wheel is rotating in the correct direction? Seems to me if you have spark at all 8 coils, the Opti is working and info is getting to the LTCC.
Last edited by Injuneer; Jun 17, 2018 at 10:07 AM.
Re: 16 years of no trouble, won't start, ideas please.
First problem with this setup using the 400 in 8 years. The codes for the LTCC pointed to two errors
2 blinks and 4 blinks
4 said check white wire. Redid to rule it out. Now it's only 2 blinks.
But then again Bob stated to someone usually you get 2 and 4 togather.
. I'm with you it seems my problem is somewhere else. Maybe something chewed a wire.
Re: 16 years of no trouble, won't start, ideas please.
You guys are awesome with your advise. I was able to escape for an hour on father's day, before my family took me out.
. I reset the connection on the ltcc and I had a black wire that came off the ignition control module that I had grounded. That ground was on by a few legs so I re crimped it. (Please correct me if I'm wrong but that black wire went from the ICM to ground.) So I double grounded it.?
Black wire C in question.
it's back to running, no I didn't check the ltcc module for faults.
Re: 16 years of no trouble, won't start, ideas please.
On the stock LT1 setup the ICM/coil bracket is bolted to the front of the driver side head. The black ground wire is short and attaches to one of the mounting studs for the bracket.
The wiring diagram you posted is not for a 93, because it doesn’t show the tach filter, which is unique to the 93. The tach wire seems to be what causes the confusion on 1993 LTCC conversions.
