Need Help. LT1 don't run...
02-09-2017, 08:52 PM
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Need Help. LT1 don't run... 1995 Trans Am LT1 auto. Has spark and runs on starter fluid. Fuel pump and tank were just replaced due to the car sitting for like 9 years (what fun) and now reads good fuel pressure at the rails.
The fuel injectors are not pulsing. I only get a positive reading on both wires and each injector during crank. So I am assuming this is related to something between the PCM and optispark.
Where I stand after todays testing is when taking voltage readings at the 4 wires that go to the optispark from the PCM I have good 12v, good ground, and 5v on each of the resolution wires from the PCM. However when I plug the harness back into the optispark, one of the resolution wires is dropping the 5v out almost down to zero volts.
Does anyone know if this points more towards a bad optical sensor or a bad PCM? Or are there any other tests I can conduct to help point me in the right direction or confirm anything? I don't have a spare PCM to plug in and test and I also do not have another known good optispark unit to plug in and test.
I tried to get readings from my old Snap On code reader that has the adapter and chip card to work with that wonky OBD2 port that is actually an OBD1 and it is not throwing any codes (reader says no codes) nor is any light flashing on the dash.
It is not the VATS has I have crank, the security light goes out after a few seconds of ignition on, and no trouble codes such as would happen if the TDM was not sending a signal to enable fuel injectors.
Any help would be greatly appreciated.
The fuel injectors are not pulsing. I only get a positive reading on both wires and each injector during crank. So I am assuming this is related to something between the PCM and optispark.
Where I stand after todays testing is when taking voltage readings at the 4 wires that go to the optispark from the PCM I have good 12v, good ground, and 5v on each of the resolution wires from the PCM. However when I plug the harness back into the optispark, one of the resolution wires is dropping the 5v out almost down to zero volts.
Does anyone know if this points more towards a bad optical sensor or a bad PCM? Or are there any other tests I can conduct to help point me in the right direction or confirm anything? I don't have a spare PCM to plug in and test and I also do not have another known good optispark unit to plug in and test.
I tried to get readings from my old Snap On code reader that has the adapter and chip card to work with that wonky OBD2 port that is actually an OBD1 and it is not throwing any codes (reader says no codes) nor is any light flashing on the dash.
It is not the VATS has I have crank, the security light goes out after a few seconds of ignition on, and no trouble codes such as would happen if the TDM was not sending a signal to enable fuel injectors.
Any help would be greatly appreciated.
Last edited by Ron G; 02-09-2017 at 09:08 PM. Reason: spelling
