I have owned a 94 Dodge Ram 1500 LST with a 318 and 2wd for 15+ years and have had the following recurring problem (as many others also have had).
<br/> I have had to replace the $200 fuel pump 4 times due to the following:
<br/> As the fuel level approaches 1/4 tank the engine will begin a gradual decline in performance then rapidly falling off to barely running on 2 or 3 cylinders (occasionally this can start happening just below 1/2 tank). It starts with a barely noticeable roughness and may go for many miles before getting worse. Then suddenly within just a mile or two the misfiring starts, one, two then most of the cylinders misfiring. It has never completely died on me and in a several situations I have had to limp 20 or 30 miles to get to a service station.
<br/> Here's the kicker: Once I put 5 or more gal. of fuel in it I can restart it rev it a little and within a minute or so it will be running fine and I can go on down the road.
<br/> I have stopped many times and checked the fuel pressure (always around 40psi), checked for bubbles (none noticeable), checked for water or crap in the fuel - from the check valve (none noticeable).
<br/> I have taken the old (replaced) pumps and bench tested them and have found no problems and they have good pressure (they make good pressure washer pumps for washing parts w/diesel or kero).
<br/> I examine the contraption that the pump, filter, and float sender are mounted in and cannot find any defects.
<br/> No fuel line problems are ever found and always replace the stupid little $20 plastic line that attaches to the h/p feed line.
<br/> I have talked to other mechanics that have no clue either but said they bought a lot of beans w/the money from replacing these idiotic devices. (Oh the good old days of spending $20 and 20 minutes once every 10 years replacing a fuel pump out in front of the parts store with a 1/2inch wrench a grease rag and a screwdriver.
<br/> My cheap solution is to keep at least a 1/2 tank of gas and a 5 gallon can in the back.
<br/> Except for the multiple water pump changes (which are also a lot of fun) I have had an excellent truck over these many years.
<br/> Any explanation would help me retain what little sanity I have and a permanent fix for this problem would be greatly appreciated.