93 LT1 no start, possibly opti?
05-22-2016, 07:13 PM
#1
93 LT1 no start, possibly opti? Alright I know very little about LT1s and their goofy design and components. My girlfriends brother bought a 93 Trans Am a couple weeks ago as a project. It had a known overheating problem. We replaced the water pump and thermostat being careful to protect the opti. Then when trying fill and bleed the system the radiator boiled over and made a mess, soaking everything in coolant. The car still ran though, so we figured all was good. We found the radiator and heater core both had blockages, so we replaced them.
After this we pulled the t-stat and ran flush through the system. When we did this the car ran like crap; wouldn't idle at all, I had to hold it at 1k rpm with the throttle to run the flush through. We had to lay on top the engine though to get the heater hoses up by the firewall, so I was worried we may have bumped a connection somewhere. This was last sunday. Fast forward to today, we go over everything one more time, all looks good and connected. We fill/bleed the cooling system again, accidentally made a little mess again with the bleeder spilling more coolant out than I was expecting. Start the car and it runs rough for about 45 seconds then dies. Now it won't start again. It cranks over, and sputters a little, like it's firing a couple times, but it won't completely start.
Does this sound like we fried the opti? It did have coolant on it when we crawled underneath. Other possible culprits? The fuel pump does prime when you turn the key.
After this we pulled the t-stat and ran flush through the system. When we did this the car ran like crap; wouldn't idle at all, I had to hold it at 1k rpm with the throttle to run the flush through. We had to lay on top the engine though to get the heater hoses up by the firewall, so I was worried we may have bumped a connection somewhere. This was last sunday. Fast forward to today, we go over everything one more time, all looks good and connected. We fill/bleed the cooling system again, accidentally made a little mess again with the bleeder spilling more coolant out than I was expecting. Start the car and it runs rough for about 45 seconds then dies. Now it won't start again. It cranks over, and sputters a little, like it's firing a couple times, but it won't completely start.
Does this sound like we fried the opti? It did have coolant on it when we crawled underneath. Other possible culprits? The fuel pump does prime when you turn the key.
05-22-2016, 08:30 PM
#2
Alright I know very little about LT1s and their goofy design and components. My girlfriends brother bought a 93 Trans Am a couple weeks ago as a project. It had a known overheating problem. We replaced the water pump and thermostat being careful to protect the opti. Then when trying fill and bleed the system the radiator boiled over and made a mess, soaking everything in coolant. The car still ran though, so we figured all was good. We found the radiator and heater core both had blockages, so we replaced them.
After this we pulled the t-stat and ran flush through the system. When we did this the car ran like crap; wouldn't idle at all, I had to hold it at 1k rpm with the throttle to run the flush through. We had to lay on top the engine though to get the heater hoses up by the firewall, so I was worried we may have bumped a connection somewhere. This was last sunday. Fast forward to today, we go over everything one more time, all looks good and connected. We fill/bleed the cooling system again, accidentally made a little mess again with the bleeder spilling more coolant out than I was expecting. Start the car and it runs rough for about 45 seconds then dies. Now it won't start again. It cranks over, and sputters a little, like it's firing a couple times, but it won't completely start.
Does this sound like we fried the opti? It did have coolant on it when we crawled underneath. Other possible culprits? The fuel pump does prime when you turn the key.
After this we pulled the t-stat and ran flush through the system. When we did this the car ran like crap; wouldn't idle at all, I had to hold it at 1k rpm with the throttle to run the flush through. We had to lay on top the engine though to get the heater hoses up by the firewall, so I was worried we may have bumped a connection somewhere. This was last sunday. Fast forward to today, we go over everything one more time, all looks good and connected. We fill/bleed the cooling system again, accidentally made a little mess again with the bleeder spilling more coolant out than I was expecting. Start the car and it runs rough for about 45 seconds then dies. Now it won't start again. It cranks over, and sputters a little, like it's firing a couple times, but it won't completely start.
Does this sound like we fried the opti? It did have coolant on it when we crawled underneath. Other possible culprits? The fuel pump does prime when you turn the key.
05-22-2016, 08:52 PM
#3
Just curious.... How the F%#* did you run an LT1 without the thermostat? They're is no reason what so ever to do that!! The LT1s thermostat has a built in gasket so it was probably oozing coolant out of the thermostat neck on top of the water pump drenching the opti! I would check to see if your getting spark first off, if so then I'd check the fuel psi. Narrow the problem down by checking the basics.
05-22-2016, 08:56 PM
#4
Ya know, I didn't even think about that. I just wanted to get the flush through the block before the engine got too hot so I pulled it out. I'm going to check the fuel psi tomorrow. I didn't have the gauge with me tonight. I'm still wondering how an "engineer" at GM thought it was a good idea to put a distributor directly under the water pump.
05-23-2016, 08:53 PM
#6
Ok so I grabbed the fuel pressure gauge and multimeter and did some testing tonight. First I checked the fuel and it primes to 45psi, so that seems fine.
Next I followed shoebox's instructions to test the ignition at the ICM connector. A and D have 11-12 volts dc as they should. B reads 2.5 volts ac when cranking which is in the range it should be if the opti is working. Lastly C reads 0.3 ohms when off, which should be good I would think.
http://shbox.com/1/4th_gen_tech2.html#opti_test
So now I'm more lost. The rough idle we experienced the time we ran it before the time it died still makes me think opti, but this makes me think maybe ICM?
Next I followed shoebox's instructions to test the ignition at the ICM connector. A and D have 11-12 volts dc as they should. B reads 2.5 volts ac when cranking which is in the range it should be if the opti is working. Lastly C reads 0.3 ohms when off, which should be good I would think.
http://shbox.com/1/4th_gen_tech2.html#opti_test
So now I'm more lost. The rough idle we experienced the time we ran it before the time it died still makes me think opti, but this makes me think maybe ICM?
05-26-2016, 10:01 AM
#7
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. Im on my third optipark for 93 they are not vented in the casing they are very sensitive. Also the cam positioning sensor is located inside thr optispark for those style. The first one lasted 4 years then bought a faulty one from summit and they sent me a replacement. They are terrible to get to and in the worst spot. If u buy msd it is able to be convertible to be vented. But they are 450 bucks. Also if you dont hear the fuel pump turn on then that could have taking a crap. That also happened to me too. First i would determine if it is electrical or fuel. Take a plug wire off and get a spare spark plug try cranking the engine and place the spark plug near the header but not touching see if you get spark. If not then optispark is not sparking to fire the plugs. The icm can go bad but you can get it checked at an autopart store. Good luck
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05-29-2016, 06:05 PM
#8
Just to follow up, we got it running. Put a new opti on it and it would start but wouldn't run well, eventually sputtering out after a few seconds. Had spark and fuel, so started looking at the throttle body and found it was all gunked up and not opening properly. Now it runs good.