Hello geniouses...have a problem, was wondering if anyone could help. 2000 gmc jimmy 4x4, 4.3L vortec. Problem started a little over a month ago. Started small, now its horrible. When it first started, the car would never start on the first try, but most of the time on the second. kept on for about 2 weeks. Thought maybe i needed to get a fuel injection/induction service. The day i got it done, the acceleration was horrible. seemed like the harder i stepped on it, the slower i went. thought maybe it was just the stuff working, cleaning etc. After the first tank, i filled it up again. then a few days later, the car wouldnt start at all. one of the guys i work with took off the air intake hose and sprayed starter fluid and voila, it started! but the next day, and since then, it wont start unless i spray it. he suggested cleaning the "butterfly" of the throttle body seeing as how it was a little dirty. The next day, it started a little rough, but after that, it went back to not starting on its own. I alternate between starter fluid and carburator cleaner at the moment, and i find that when i use carb cleaner, it accelerates a little bit better. I just replaced the whole fuel pump assembly a little over 2 years ago(with an aftermarket pump, not one from the dealer) and it has a brand new battery. Usually if i turn it off and run in a store, it will start back up, but after it sits for a few hours(as little as 2) it won't start unless i do my ritual. Where should I start? Any suggestions would be helpful! Thanks so so so much in advance!

P.S-So i dont waste anyones time, these are a few things i have done already...
1) added dry gas
2) someone suggested perhaps a fuel injector was clogged, so i added a cleaner to the gas tank, still nothing
3) Changed pcv valve
thanks again!

My guess is if it starts with starter fluid but doesn't run you have a fuel problem. Check pump pressure & leak down. Possible fuel pressure regulator. I know guys that have had short life with after market pumps depending on where you bought it.

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

it runs after i get it started, but when i go to drive it, it doesnt want to accelerate..Like when i step on the gas, the car wont pick up speed, but the rpms go up. but if i butterfly the pedal, it will accelerate a little bit. If i use the carb cleaner, it runs a little better than if i were to use the starter fluid. so frustrating when the people in the slow lane are honking and screaming at me...lol

ok so MT, where would i get this machine that will test the fuel pressure? and how to you check it while you are driving? Is this the machine that i will hook up to the valve on the fuel rail? because if so, then i think i know which one you are talking about.

No machine just a fuel pressure testing gauge and long hose and a scrader valve adapter to it you fuel test port scrader valve.
Parts places or tool dealers sell them.
And some parts places loan/rent them.
Or any good repair shop can test it for you.
Post back the fuel pressure as outlined.

No machine just a fuel pressure testing gauge and long hose and a scrader valve adapter to it you fuel test port scrader valve.
Parts places or tool dealers sell them.
And some parts places loan/rent them.
Or any good repair shop can test it for you.
Post back the fuel pressure as outlined.

I bought one at Harbor Freight for $10 USD. Check their website.

ok so status update. My dad came down and went to autozone and rented the fuel pressure testing kit. This is how the day went. First test:
turn key forward-ranged anywhere from 46-50 psi
cranking-42 psi
running-54 psi
off-60 psi
My dad then suggested changing the fuel filter, so we did. after replacement of the filter we did it again. second test:
key forward-52 psi
running-52-54 psi
off-60 psi

I told my dad what MT said about pinching the return, but he said its all metal, so he couldnt do that. After i replaced the fuel filter though, i have noticed that it accelerates a lot better...I can actually pass people now! But, we went to the parts store and bought a fuel pressure regulator and we were going to change it, but appearantly its a lot of work. Someone else told me it could be that i need a tune up with plugs and wires and such. So my question to you, how likely is it that it is the fuel pressure regulator? do you think there is something else it could be? Its $100 for all the parts i need for a tune up, and $40 for the regulator, but a lot of work. what should i try first?

Fuel pressure is low.
You need to go threw the complete fuel pressure test as outlined in upper post and post back pressures.

If you can not pinch a return line off plug it or check direct fuel pressure at fuel filter in line.

PS: Fuel injection cleaners do nothing, don't waste your money on them.

I agree with MT-2500, pressure is low, changing the regulator without first finding it to be the problem is almost guaranteed a waste of money that could be spent on the likely failing fuel pump. Make sure to get a really good AC Delco or Delphi fuel pump as all the rest are junk.