1991 626 fuel pump problem

I recently got a 91 626 from my brother. It sat in his driveway for about a year. I put a battery from another car in it - and it started up fine, except at idle it would intermittently cycle from idling normal to high, up and down - up and down. This only happened when I was stopped and in 'park'. I had it in the shop to replace a tailpipe and they called me to tell me it wouldn't start. It cranks fine but doesn't start. Eventually they tell me the fuel pump is bad. They replaced it and I drove it home. The next day in the afternoon; after driving it to and from work, the same thing happens. After getting it towed to the shop they tell me the fuel pump is bad, again. They repalce it and drop my tank to clean it suspecting dirt or something in the tank caused the problem, and also to maintain the warranty on the second pump. I get the car back and a day later the same thing happens. It drives fine for a day or so then out of nowhere it will not start. I thought I might have noticed the idle start to rise as I was turning the key to stop the engine this last time. I am wondering if the idle could have anything to do with the problem, and if anyone out there might have some insight to what is causing my fuel pump to crap out on me after a day of working fine.
Thanks
Chris

Nooo... The high idle is trying to tell you, there is a problem, the computer is trying to maintain the correct air/ fuel ratio. Number one, replace fuel filter it is clogged. Two add a bottle of injector cleaner to a full tank of gas. should help a bunch. Then drive every day for about a week, and it should clear up. Is mostly varnish from bad gas after sitting for a year. Hope this helps. Later... Mark.

Thanks, mark. I got a third fuel pump (from a different manufacturer)and it's running good. I also took your advice, plus changed the thermostat (the temp guage would rise while sitting at a light - and would go down when I started driving or revved it in neutral) She's running like a champ.