96 GMC Jimmy Engine cut out

Last night I had the strangest problems with my 96 GMC Jimmy. (Bear with me)
Driving on a very hot day (38*C, 101*F) we drove about 30 KM, I had to slow down for a left turner, I gave the truck some juice, it started to
accelerate, then seemed to cough, and then flat-lined. The engine just stopped.
Having experienced this once before, I swore, got out, beat the gas tank with a handy stick, jumped back in and it turned over right away. I hastily turned tail and headed for home.
Clear cut case of a bad pump, right? Read on!
We drove about 10 or 15 minutes and it died once again. To myself I said "That's it! A bang will get it going once, almost never twice." but since I had my wife and 2 of my 3 kids with me, I dutifully got out and banged again. To my amazement, it turned over once more.
3 minutes down the road, it quits yet again. This time I pull over, count to five (no hitting this time) and try cranking again. She starts right up.
This time we made it 25 minutes and were 1/2 block from making it home before it quit yet AGAIN. Once again I counted to 5, turned it over and it started right up.
An hour later we drove it to the bank and back, just to see. Started fine every time.
This morning my wife took it out for a quick trip, no problems. Then I drove it to work, again no problems.
PLEASE tell me someone has a good idea what this might be. I'm not a mechanic, but am a pretty good hobbyist. This has me stumped.
Details: 96 GMC Jimmy SLT 4.3 Liter Vortec V6 344,000 KMs 80,000 (+/-) on the last pump.
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It still sounds like a fuel pump getting weak to me.

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Chris wrote:

You MIGHT have corrosion on the positive battery cable/terminal connection. When it happens, turn the key to start (the motor does not turn over). Have someone gently wiggle the positive battery terminal (while you hold the key in start). Make sure everything (arms-fingers...) is clear of rotating parts. To fix it. Take the positive terminal off. It has 2 cables attached. One of the cables feeds the starter, the other feeds everything else. Split the rubber boot and separate the terminals and spacer washer. There will likely be a lot of corrosion here. Wire brush everything good and soak in baking soda solution, then wire brush it again. Once you have bright metal, reassemble the terminals, washer, and bolt. Now there are two schools of thought here for what to do next. One says to coat the terminals with vaseline to inhibit corrosion. The other says to coat the terminals with an insulating rubber compound that you can brush on. I have used the vaseline solution with great success. Be carefull around the battery after this, as there is an exposed 12 volt source.
KenG
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Fuel pumps either work, or they don't. No in between. The truck has never stopped turning over, so it's not a battery post. The engine quit, but still had volts showing on the dash.
Suggestions have been: 1) Crank shaft sensor 2) Distributor cap
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well i must tell you that three of us had that problem and in each case it was solved by removing the battery cables and REALLY cleaning them good. 1. scrape of corrosion inside cable connections(they sre corroded and you cannot see it without removing them) 2.rinse with baking soda mixed with water to a paste mix 3. make sure connecting bolts are in good shape 4. clean the battery cable mount faces
rinse cleaned terminals with clear water to remove paste residue. remount to cleaned battery connections reattatch all cleaned parts. in every case, the starter would turn the engine over, but if it even started, it would run rough and the dash lights would indicate stop,start go
old john

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I'll give it a shot when I replace the distributor cap tonight.
It's been almost a week, haven't touched it and it is still running fine. No warning lights on the dash, now or then. Has been running rough (once in a while, for a moment or two) and hesitating once in a while for some time though, so can't hurt to try.
Thanks for the advice no matter.
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