92 LTI No Spark
Thread Starter
Heel & Toe
Joined: Sep 2019
Posts: 17
Likes: 1
From: Louisiana
92 LTI No Spark
I have a 92 convertible with an LT-1. I changed the plugs and wires about a month ago and the car ran great. Tried to get it out this past Sunday and it won't start. It cranks fine, but no start. I couldn't hear the fuel pump running when I turned the key on. But it also has no spark.Is there something in the ECM that would shut down the spark if there's no fuel pressure? I haven't been able to check the fuel pump fuse yet, it started raining again before I could move the car out to get to the fuse box. Does anybody have any good ideas?
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,628
Likes: 4,071
From: Cape Coral, Florida
If you believe you have a fuel delivery issue spray some Brake Kleen into the intake and see if it starts or tries to start...this is an ignition related by the "Master"...it may help in your diag...the car is a 1994 !!
Last edited by C5 Diag; Sep 4, 2019 at 12:37 PM.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,628
Likes: 4,071
From: Cape Coral, Florida
Not sure !!...if it does it would shut down fuel if no spark...not the other way around...you don't want to pump all that fuel into the combustion chamber !!...that was actually something I wanted to test on my C5...disable the coil and see what the injector does !!
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
There are lots of 92-93 LT1 no start threads you might search them. Opti sends signal to ECM. ECM activates injectors and sends signal to ICM. Injectors can still pulse with no spark or pressure. ECM can still turn on ICM as long as it can process signal from Opti.
Fuel pump coming on doesn't mean adequate fuel pressure.
Manuals would be handy if you intend to DIY.
Tools. Spark tester. Fuel pressure gauge, Noid light, DVOM, test light, obd1 scanner hand held or laptop/tablet.
Fuel pump coming on doesn't mean adequate fuel pressure.
Manuals would be handy if you intend to DIY.
Tools. Spark tester. Fuel pressure gauge, Noid light, DVOM, test light, obd1 scanner hand held or laptop/tablet.
Thread Starter
Heel & Toe
Joined: Sep 2019
Posts: 17
Likes: 1
From: Louisiana
To answer all the replies. I haven't been able to check for codes yet. But I did for check spark with a tester on 2 plugs and at the coil. Tester showed no spark. Hoping it's not the opti!
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Drifting
Joined: Jun 2018
Posts: 1,678
Likes: 229
From: Michigan
To your original question, there is nothing that shuts down spark for lack of fuel. The ECM doesn't monitor fuel pressure. It shuts down fuel for lack of spark so it doesn't dump raw fuel in the engine. If you hear the fuel pump running, you have fuel if the injectors will fire.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Sounds like you have a spark problem but I would always check for spark first off the coil.
Wrote this up few years ago to check if there is voltage drive to the ICM to determint if the ICM is bad or if it could be ECM or opti, or something else.
Here are a few tests to get you started on the problem. Be the utmost of careful not to short anything to ground. ING key off, remove ICM connector and check the ground connection on pin C -BLK/WHT wire, (resistance about 0) .
Next, “Key on”, check for 12 volts DC at pin A - PNK /BLK wire and pin D – Dark green wire. If no voltage check the coil fuse 10A, (#25), or wiring.
ECM voltage drive check;
If all is good, set meter to read AC volts and connect probe to terminal B - white wire. Have some one crank engine, meter reading should be between 1 to 4 volts. If OK, this indicates opti and ECM are probably working and ICM possibly bad. If no voltage, opti or ECM could be source of problem. Figuring out which one might take some doing and would be phase 2.
Wrote this up few years ago to check if there is voltage drive to the ICM to determint if the ICM is bad or if it could be ECM or opti, or something else.
Here are a few tests to get you started on the problem. Be the utmost of careful not to short anything to ground. ING key off, remove ICM connector and check the ground connection on pin C -BLK/WHT wire, (resistance about 0) .
Next, “Key on”, check for 12 volts DC at pin A - PNK /BLK wire and pin D – Dark green wire. If no voltage check the coil fuse 10A, (#25), or wiring.
ECM voltage drive check;
If all is good, set meter to read AC volts and connect probe to terminal B - white wire. Have some one crank engine, meter reading should be between 1 to 4 volts. If OK, this indicates opti and ECM are probably working and ICM possibly bad. If no voltage, opti or ECM could be source of problem. Figuring out which one might take some doing and would be phase 2.
Thread Starter
Heel & Toe
Joined: Sep 2019
Posts: 17
Likes: 1
From: Louisiana
sounds like a good starting point, I'll try this afternoon. I've had this car for 7 years and this is the first time it never started. I checked for spark on 2 plugs and had nothing. I suspect the opti, but I'm holding out hope that it's not
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
SOME LINKS FOR OPTI TESTING;
https://www.corvetteforum.com/forums...ls-to-ecm.html
https://petrisenterprises.com/blogs/...roubleshooting
https://www.corvetteforum.com/forums...ls-to-ecm.html
https://petrisenterprises.com/blogs/...roubleshooting
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Thread Starter
Heel & Toe
Joined: Sep 2019
Posts: 17
Likes: 1
From: Louisiana
It's running again. Everything pointed to the coil. When I took it off it was the original coil and ICM. I guess 27 years isn't a bad life span. (I'm sure the new parts won't last that long) Changed both and it cranked up. My thanks to everyone for their help.