Won't start without ether.

Hi,
My 2000 4.3 Express cargo van will only start if I spray starting fluid into the air intake (actually carburator cleaner seems to work better). I have 108,000 miles on it and changed the plugs last month. New plugs didn't help.
Its been this way for about a year. It runs great, great power, no change in gas mileage (14-15 in town, 17.5-20 highway... I drive real easy).
About a year ago (15,000 miles) it was getting harder to start when cold. But it got worse till now it won't start w/0 ether after sitting just 15 minutes.
I put a fuel pump in it a few years ago (I cut a hole in the bed and changed it from the top without removing the tank, very slick and easy).
Ant suggestions?
Thanks,
Thomboz

Have you checked the fuel pressure. Your pressure regulator may have low fuel pressure to the injectors.

As said low fuel pressure.

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.

And if pump is bad only replace it with a AC-Delco/Delphi fuel pump.
MT

Thanks for the advice. I last replaced the fuel pump with another brand and somehow lost a few accessible gallons in gas tank capacity.
What do I need to test fuel pressure? I'll head down to my local Auto Zone as they rent tools, but they don't always know what tools they have and what they do.
Thanks,
Thom

Tell them to look up a GM fuel pressure tester.
You will need one capable of reading a 100 lbs fuel pressure and a scrader type hook up fitting to hook on to your fuel rail.

Have you been running the tank low or under a 1/4 tank of fuel?