Need help on 94
Thread Starter
Burning Brakes
Joined: Oct 2005
Posts: 1,020
Likes: 18
From: Anderson SC
Need help on 94
What do I look for when the car doesn't fire? I've changed plugs, swapped out computers, swapped out ign module and coil and still nothing. What should the plugs going to the ignition module and the coil read? How do I check to make sure they are sending the correct signal to the coil/ign module? The car ran rough the last time it was driven and then was parked for a month or more and now won't fire. The car is getting fuel up to the fuel rail and the fuel pump is new and working also. Help please! Again, it is a '94.
Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
pull a wire off of the plug, hook up a spark trester if oyu have one (preferred) or if not use an insulated set of pliers to hold the wire near the block while a friend hits the key.. you are watching for the spark to jump from the wire to the block.. if no jump, i suspect the optispark.. if it does jump ohm the injectors.. (they should all be within 1.5 ohms of each other - i think, someone else please verify this number). if they ohm out, you have fuel to the rail (41 psi) and the spark jumps it sounds like the timing chain jumped (rare on an LT1)..
good luck let us know how it goes
good luck let us know how it goes
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
There are many places to start, hear is one to check part of the ignition circuit systematically.
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 Ignition Control Module connector and check the ground connection on pin C - BLK/WHT wire, (resistance about 0) .
Next, “Key on”, check for about 12 volts at pin A - PNK /BLK wire and pin D – Dark green wire. If no voltage check the coil fuse 10A, (#25), or wiring.
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. Key off! Put connector back on. If OK, this indicates opti and PCM are probably working. If not, opti or PCM could be source of problem. Opti is most likely, (optical portion). If all is good, the Ignition Control Module could be defective. Although the coil could cause the same symptom, the ICM is more of a likely candidate.
To eliminate the coil wire, attach another wire from coil and hold near ground while some one cranks engine. If is arks, coil wire could be bad usually near the water pump.
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 Ignition Control Module connector and check the ground connection on pin C - BLK/WHT wire, (resistance about 0) .
Next, “Key on”, check for about 12 volts at pin A - PNK /BLK wire and pin D – Dark green wire. If no voltage check the coil fuse 10A, (#25), or wiring.
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. Key off! Put connector back on. If OK, this indicates opti and PCM are probably working. If not, opti or PCM could be source of problem. Opti is most likely, (optical portion). If all is good, the Ignition Control Module could be defective. Although the coil could cause the same symptom, the ICM is more of a likely candidate.
To eliminate the coil wire, attach another wire from coil and hold near ground while some one cranks engine. If is arks, coil wire could be bad usually near the water pump.
