Funky fuel system problems.. starving after 1/2 tank

[gintaras]

UPDATE, the problem was the fuel pump, and I have replaced it, but I am concerned about not having the correct one..

my original pump has 3 lines.. one from the tank, one to the carb, and one, for what I thought was a return line, but now I don't know..

parts store gave me one with only a supply and a line to the carb.. when I told that mine had a return they told me "no, that goes to the charcoal canister, just plug it up.. so I did just that, runs great, but I think I need the one with the extra fitting on it, I think it is a return... anyone?

I just got back from a 1200 mile trip from TX. I will post more about that in another thread after I get some sleep, but boy are those foam bench seats VERY uncomfortable after a long haul like that!


Let me run down the symptoms which I feel is a fuel issue..



First of all, the truck only has 68k miles on it, and only accumulated 1500 miles in the past 4 years until I added 1200 this weekend..

We were going along just fine, about 65-75mph.. when all of a sudden, 120 miles into our trip, I get some hesitation, and I find myself driving slower and slower.. the engine is bucking, and seems to get a lot worse if the secondaries kick in. and it seems to accelerate when the fuel sloshes around, kind of like a rhythmic accelerate, fall, accelerate, fall, accelerate, etc... I get down to 40 mph and have no choice but to pull over and shut it down for about 15 minutes and then it runs fine for a while. Also experiencing very rough idle, no matter if the tank is full or 1/2, but a little pedal smoothes it out.. this was not happening prior to hitting the highway.

I noticed that this happened after I hit the 1/2 tank mark..

I didnt think it was a fuel problem at first, so I cleaned the points on the road with a dollar bill, replaced the coil and the fuel filter in the carb.. we filled up and thought it was fixed but then again at 1/2 tank we were limping again.

I pulled out the feeder and return assembly and the screen was not restriced, so I put it back in.. oh, important note, the return tube was shorter than the supply tube, not sure if that is a problem or not, and the funny thing is that the return line seems about as long as a 1/2 tank...

another full tank and another 125 miles, again, limping..

So, from Houston to Chicago, stopping every 120 miles kind of sucks, and the 18 hour trip turned into 29.. with all the stops and troubleshooting.

Sorry for the long post, going on 36 hours no sleep, I am off to bed now!