1991 Isuzu Rodeo Won't Start

Find the timing mark on the main crank pulley. When the marks are aligned, the #1 cylinder should be at top-dead-center. Pull the #1 spark plug and use a wooden dowel to check. Put a socket on the main crank pulley bolt and go on and off the mark. The raising and lowering of the dowel should match. Of course, this will only tell you if there was a big change, only one or two teeth, you won't be able to tell the difference. Just a quick check.

Possibilities;bad fuel- clogged injectors-mechanical fault in cyl/s inc broken v/v spring. Do compression test.

It also could just be a bad ECM? I had a car with similar symptoms; it would intermittently stall and/or lurch very badly. Has the "check engine" light ever come on? Is the battery voltage and the alternator output okay? Just my $0.02... good luck!!

Okay... to those few of you who responded... thanks for the suggestions. Here's what I did to fix the problem. During the afternoon, I put an induction timing light on the #1 spark plug lead, and turned the engine, but could not see the light on the timing marks, so waited until almost dark to try again. Well, once again, the timing light was too dim to illuminate the marks. In fact the timing light would not fire at all (indicating that the voltage in the spark plug lead was too weak to fire the light), but I heard a strong spark firing in the area of the new coil and when I glanced toward the sound I saw a spark jumping from the coil-to-distributor ignition lead to ground on the top of the coil. I pulled the lead off of the distributor and found massive corrosion at the terminal that was disrupting the spark, and the insulation on the lead was bad in a couple areas. A substituted lead fixed the problem. Yeah!