First check for diagnostic fault codes. When the Check Engine light turns on there WILL be at least one code in memory. When the light did not turn on, as in your case, there still COULD be codes. Not all codes result in the light turning on.
Cycle the ignition switch from "off" to "run" three times within five seconds. Shortly after the Check Engine light goes off it will start to flash out two-digit codes. The first one will usually be one flash, a short pause, then two flashes, then a longer pause before the next one starts. Code 12 just means the ignition switch was turned off and can be disregarded. The last one will be code 55 which can also be disregarded. It's the codes in the middle that are important.
To check for spark after the engine stalls, unplug one of the front spark plug wires from the spark plug and hold the brass terminal about 1/4" from a metal part of the engine. Hold it by the rubber part of the wire. Because of the risk of getting jolted, I prefer to poke a screwdriver into the terminal and set it with that 1/4" gap. You should see about two sparks per second while a helper cranks the engine.
If you're alone you can crank the engine from under the hood so you can still see the spark plug wire. I think the '90 models still had metal relays bolted to the left inner fender. If you do, find the one that has a red, brown, black, and one or two yellow wires. That's the starter relay. Unplug it and jumper the red and brown wires in the connector. They will be the two fatter wires. You can use a piece of wire or a stretched out paper clip, but there will be about 20 amps going through it so those could get hot. I use a stretched out cotter pin.
The newer style relays are shown below. If you have that style in the under-hood fuse box, remove the starter relay and connect terminals 30 and 87 in the socket with the cotter pin or paper clip. If you think you might be doing this a lot, a better method is to pop the cover off the relay, reinstall it that way, then just squeeze the contact. It won't hurt to leave the relay cover off for a few weeks. Just put the cover back on the fuse box to keep rain water out while you're driving.
If you find a constant steady stream of sparks yet the engine doesn't run, you have a fuel pump or injector problem. If there is no spark, smell for raw fuel from the tail pipe. If you do smell fuel, you likely have a problem with the ignition coil pack. (The single coil was the cause of the intermittent problem on my 3.0L a few months ago. The symptoms, however, were unusual enough that the coil was ruled out until it finally quit completely).
In the most common scenario you will find no spark and new fuel smell. I always like to double check myself by measuring the voltage on the dark green / orange wire at the coil pack, one of the injectors, or the small terminals on the back of the alternator. A test light works best. You can use a digital voltmeter too but you might miss the first part of the test. If a helper is turning the ignition switch for you, you should see the test light turn on for one second then it will go off. That proves that part of the circuit is working. What's important is it must light up again during engine cranking. If it does not, there is a problem related to the crankshaft position sensor or the camshaft position sensor. Your test light is telling you when the automatic shutdown (ASD) relay is turning on. It turns on for one second after turning on the ignition switch and it turns on again when pulses arrive from those two sensors.
Friday, February 25th, 2011 AT 7:23 AM