fuel pump?

im getting major hesitation from mother-in-law's 97 s-10 4.3l eng X. it starts off great but the more it warms up the worst it gets. ive replaced all the vacuum lines, the fuel pressure is perfect according to the book. replaced the fuel filter, vac tested the regulator. if it quits, turn off a couple of seconds, and it fires right up. the pump is making a lot of noise, but the pressure is good(by the book). my wife did run out of gas about the same time as the problem started. could she have damaged the pump? what about the pressure being within spec? if i take off the air collector from the throttle body, it will die out like it has too much vacuum!

I know that you replaced the fuel filter, but I'd almost take it off again and blow it out. You might have gotten a lot more junk in there some how.
Also try Gas Line antifreeze.

I wouldn't replace the fuel pump right now if it's up to spec's, It's a big job and an expensive part.
And when you do have to replace it, drop the tank and flush it right out.
It'll help save the fuel pump and keep the fuel filters cleaner in the future.

If it's really noisy you might want to change the fuel pump right before it gets cold out. That would be a bad time for a break down.

thanks for your reply

i checked the filter, and its clean as a whistle. i removed the filter and ran the pump a few times. it seems to be comming out pretty good. i dont get it. when the truck is cold you can get in and go without any problems, runs fine, but when it reaches normal operating temp it goes south! could i be missing some vacuum lines or something? there dont seem to be a lot.

The easiest way to check the vacuum is spray wd40 on the lines, and anywhere that you might have a leak.
It's suposed to suck in and cause the engine to rev up.

To be perfectly honest I've never been lucky enough to have it work for me, so for all I know it's a wives tale. But I've also never had a large leak or an open hose

Also check the coolant temp sensor. If its going bad it will tell the computer the wrong info when the engine is hot. The best way to test your fuel filter is to first remove it then drain the gas from it and put it to your lips and blow through it. If there is any resistence replace it. You could have good fuel pressure but low volume,. By running the tank dry you will pick up lots of crap thats in the tank also that is a sure fire way to kill the fuel pump. The intank pump needs gas as a lube and to cool the pump

thanks guys

the filter has no resistance. the temp gauge seems to be o.k., but ill try to check it out. what about vapor-lock. im thinking its the sensor or the gas cap, maybe im right. if its either of these two im gonna loose my mind cause i already bought a new pump.

Vapor lock is old school fuel pump problems. Your system runs a high pressure so vapor lock is not your problem. Dirt in the injectors , the problem started after the fuel tank was run dry right?? You dont have a vacuum leak if you did you would have a high idle and a check engine light on run a few cans of injector cleaner in it and see what happens

ill give it as much time as ia can. i just dont get it why i have fuel delivery problems only after if reaches normal operating temp. when the engine is cold, i can jump in and take off with no problems. ten minutes later it starts bogging down. somebody told me maybe its the cat converter. any thoughts on that?

One thought is fuel pressure. This system needs 60-66 psi. If it gets low or starts to go below 50psi you will start to see a running problems.
The muffler shop can run cat back pressure test for you. But It should cause problem hot or cold.

the fuel pressure holds steady where the book states it should be. what could cause the truck to run perfect till operating temp then awlful when it reaches temp? ive replaced the coolant temp sensor hoping that it could give an incorrect signal to the computer, nothing different. is there another sensor that reads temps that could affect the fuel supply? map, airflow,air intake, etc.?

My truck would fire right up when it was cold.Once it warmed up and I shut the truck off and then restarted it,it would crank a bit before it would fire.Turned out to be the fuel pump.

Have you checked the cat? (just throwing it out there) a clogged cat can cause the same symptoms.

i read in another post to put on the pressure gauge and run it behind the hood and drive the vehicle and monitor the pressure. i did it and the pressure was running good it never droped below 50psi and usually stayed around 58 to 62 or so. ill check the cat next. my wife is drving me crazy to replace the pump because i already have a new one, i almost agree but.... the pressure is always within spec. the pump is noisy, but its working!

i read in another post to put on the pressure gauge and run it behind the hood and drive the vehicle and monitor the pressure. i did it and the pressure was running good it never droped below 50psi and usually stayed around 58 to 62 or so. ill check the cat next. my wife is drving me crazy to replace the pump because i already have a new one, i almost agree but.... the pressure is always within spec. the pump is noisy, but its working!

50 is wayyyyyyy too low, it should be a constant 60-64 at running

i dont mean to beat this thing to death, but my haynes manual states 55-61 psi. for the CFSEI? engine and 3 - 10 psi. drop when running at idle. last night i drove the truck for 45 minutes without any problems. when i cut off the engine and restarted it instanatly gave me problems. now that i think about it, it seems that since ive been having this problem it always does good till i stop the motor and come back to restart. also, when its cold, the pressure is up but the idle speed doesnt seem high enough for when its a cold engine. ive got an autoxray code scanner and get no codes. ive still got to check the cat. what about an oxegen sensor? dont want to rule anything out but, i just dont think its the pump! maybe im wrong!

update
last night it was running like a champ, spinning the wheels off, running 80 -90 mph with no problem for as long as i drove it. when i cut it off and restarted, here we go again. this time i noticed that the fuel gauge was wayyyyy wrong and not holding a constant value. maybe the fuel pump ground or another wire. the oil pressure was moving back and forth just a little while at idle, maybe this is normal. will take any suggestions! thanks guys!