95 Caravan blows fuel pump fuse...replaced fuel pump twice

I've got a 94 Dodge Grand Caravan 3.3L, front wheel drive. I was going down the highway when the fuel pump fuse blew. I immediatetly put in another fuse and it blew after turning
the ignition on, but before cranking the engine.
I towed it to the local Tuffy's and they swapped out the fuel pump (I had them install an Airtex fuel pump ($160) instead of the regular AC Delco fuel pump ($350) they normally install.) They also replaced the 6ft(?) wiring harness that connects to the pump assembly, and they swapped out the fuel pump relay. (They normally replace the fp,relay, and harness, even if only one of these is bad.)
It ran okay for about 6 hours then blew the fuel pump fuse again. After about an hour, I installed another fuse and it ran fine. I took it back to the shop to diagnose why the fuse blew though. It ran fine for them for a while and then blew the fuse. They mentioned that the new wiring harness also melted during testing. So they again replaced the wiring harness and fuel pump with another Airtex fuel pump.
It ran okay for about 4 hours out of the shop and then the fuel pump fuse blew again.
One thing I have noticed and the mechanic noticed as well, if you start the engine while it's cold, there isn't any problems. If you turn the engine off and then restart it while it's still warm, the fuel pump fuse will either burn out immediately upon turning on the ignition, or it will usually be fine until you try to crank the engine again.
The mechanic also disassembled the fuse block under the hood but didn't see any problems.
The guy I spoke with at O'Reilly Auto Parts was the one that suggested the Airtex fp. He mentioned he had 5 years experience with Carter fp's and 5 years experience with Airtex fp's and said he has had about half as many returns with the Airtex units.
I've found a post by someone else that seems to be having the same problem, with the same year model:
http://www.autowhiz.com/messageboards/message.php?id 09
Any ideas would be appreciated.
Thanks, Jeff
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How about the fuel regulator on the fuel rail being shot and pump pressure going through the roof, thus causing too much current draw, thus blowing fuse etc. Of even a plugged filter.. Have a pressure check at the fuel rail.. Maybe even the return line to the tank is plugged. Just a guess.. Lottsa luck.. ;-)
eff Frohwein wrote:

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Don Ocean wrote:

Thanks Don. I had them check all of these but no luck. They gave up on it since the problem is very intermitent and they weren't getting anywhere.
LUCKILY, they gave me the ALLDATA wiring diagrams they had printed out. (They got these from alldata.com, I assume.) In these diagrams, I found the fuel pump relay. This part of the electrical system was missing from the Haynes manual I bought. :-\ With the ALLDATA daigrams I noticed the oxygen sensor also connects to the fuel pump relay output. After inspecting the oxygen sensor cable leading to the oxygen sensor, I noticed what appeared to be friction-related wear of the cable exposing wires.
I'm not 100% sure that is the problem, but so far with the oxygen sensor unplugged I haven't blow any more fuses.
Thanks, Jeff
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