Yesterday evening as I was driving home from work, all of a sudden my
>'97 GMC Sonoma (4cyl) makes a quick "thump" sound and a gentle lurch
>(it felt as if I had driven over a cardboard box or something on the
>road - not an intense feeling, but definitely noticeable), then the
>truck lost all power and stalled. I managed to get it on to the
>shoulder, and now the engine tries to start, but will not turn over.
>Also, as soon as I turn the ignition on, I notice it has NO oil
>pressure. All my gauges were reading normal before this, and we've
>had no other engine problems since we've owned it. We've never had
>any puddles or anything under the engine block, no smoke from the
>exhaust, nothig out of the ordinary.
>
>It's at the mechanics as I write this, I'm just wondering if anybody
>might have some idea what the problem might be. (I'm keeping my
>fingers crossed that it's something simple!)
>
>Thanks!
The gauge WILL read no oil pressure when the truck's not running. I had a similar thing yesterday on my 4.3, had a slight thump, radio turned off then on, but the truck never stalled. Noticed my voltmeter was reading REALLY low, my alternator died. Was able to get where I was going and then home, replaced the alternator today. You may have a similar situation. I know newer vehicles don't like to run if the voltage is too low.