I have mentioned this already some time ago but do not recall. 85 Toyota supra.
What does it mean when a car will not spark while turning over but at times gives off one spark sometimes when you first start to turn over and once always when you stop turning it over.
This engine was running at one time in a diff car. The distributor was removed from the engine. But putting it back in I set to top dead center. Cylinder for 1 is all the way up and the marks on the cam shafts marks are lined up. I set the rotor pointing to plug 1. So the distributor should be set right.
Looking at similar problems. I’ve found none like this exactly. But suggestions for that was starter or ignition switch. I would like to know what causes a no spark while it’s turning over for as many times as its turning and then to give one bright spark once you stop turning it over.
These modules function two modes.These are the start and run modes,
When starting the engine, the module allows full battery voltage to the ignition coil. Once the engine starts, the module drops the voltage to the ignition coil.
So, the module may have failed in the start mode but not the run mode.
And that’s why you see that single spark.
If the vehicle has a manual transmission, this can be verified by push starting the vehicle.
Suggest you first determine what sequence of events is designed to cause a spark when engine is rotating. No experience w/your engine, but one guess, a sensor inside the distributor senses the engine is turning and the ignition module (or perhaps a engine control module computer) determines from that sensor’s signal when it is time to fire the coil. If that’s how it works, first step is whether or not the sensor inside the distributor is working properly.
I expect you already know this, but there’s two TDC’s in an engine cycle. One is at the beginning of the compression stroke, and the other is the beginning of the exhaust stroke. Are you certain your timing setup is using the correct TDC?
I don’t remember what vehicle it was, but it was old and had throttle body injection. Had the same problem. Trouble shot everything down to the ECU. Had the opportunity to swap ECU with an identical truck. Both trucks started and ran beautiful after swap so I marked it as dirty or corroded ECU pins as the problem. In this vehicle the ECU controlled the spark switching from start to run.
Both of your examples are at BDC (bottom dead center)
TDC (top dead center) is at the end of the compression stroke, that is why you put your finger over the spark plug hole and wait till you feel compression then finish turning the engine by hand bringing it up to TDC, the other time it hits TDC (180 out on the camshaft) is at the end of the exhaust stroke (pushing the exhaust gases out)…
And a distributor that is 180 degrees out will still fire, but it will be firing at the end of the exhaust stroke/beginning of the intake stroke (valve overlap) causing back firing through the intake…
oops! @davesmopar is absolutely right. The possibility still applies however that the OP’s timing might seem correct, but could in fact be set 180 degrees out of sync.
Can you say fire in the hole… cause fire will be coming out of the carburetor if it has one (yes I know the OP’s vehicle is NOT carbureted, just using for reference)…
I am with Tester on this one, I think it is the ICM (ignition control module)… Possible ignition switch but more likely the ICM
Toyotas back in those years had an ignition system device called the Igniter - in addition to the distributor, which included, instead of the superceded “points,” an electronic “signal generator” also known as the pickup coil. Some makers called it an ignition control module.
IIRC the Igniter was a heavy black box with several wires and maybe a transformer inside. Maybe that has failed.
I know on older Chrysler products, a failed ballast resistor would give this system. It provided the reduced voltage in the run mode the same way that the ign. control module that tester described so I think tester is right.
