2004 lesabre. 3.8L 136,000 miles....

Car would run perfect for about 10 minutes then start chugging and sputtering like it was running out/gas..

Now it wont hardly run at all. I replaced the fuel pump in May 2017 with a Delphi OEM..

Ok, i removed the OUTPUT line off pump and attached a hose to the pump and ran into a plastic jug.

The fuel line is primed still leading to engine.

I turned key to ON position and a little bit of fuel pumped into jug..

I started engine and the fuel pumped like crazy into jug continously AND the engine ran SMOOTH until it used up the fuel in the line that is DISCONNECTED from the pump..
So, the car will run ONLY IF the OUTPUT fuel line is OFF the pump.. (until it uses up the primed fuel in line)

But soon as i put the fuel line back ON the pump, car will NOT run..
Almost like its creating a vacuum that wont allow fuel to flow with line on ??

Have you tried running the engine with the gas cap off?

Doesn't really make sense, since when you open end the fuel line, the line going to the rail may have fuel in it, but it has no pressure....so even with an injector opening up, there is no pressure behind it....

Have you checked fuel pressure, at the fuel rail?

Last time fuel filter changed?

fuel filter has not been changed in the 40,000 miles i have owned it.. I have tried with fuel cap off and no change..
The car runs for about 3-5 seconds with output line off at pump.. the return line is attached.

And what is the middle port on pump for with no line ? Thx so much

has 50 psi on rail

This is turning into a mystery, for sure.......I assume you are disconnecting the line out of the fuel module, from the trunk?

You have 50PSI, but we don't know if that is just static pressure....

Since you like to work with hoses......you attached a hose in the trunk and saw a good flow rate when cranking the car(turning key to on, pump is only on for a few seconds, cranking the vehicle it is on constant)......

Disconnect the plastic line at the fuel rail, and insert the plastic line in a suitable gas container......remove harness from ICM(one 7 mm screw).....this prevents spark and injector pulse.......now have someone crank the vehicle.......if flow rate is much less than what was coming out of the trunk, then replace the fuel filter.....

Or, take some carb cleaner, and spray into the intake, while cranking the vehicle......if the car runs as long as you spray, and dies when you stop, check for injector pulse...if you have injector pulse, replace the fuel filter.....

excuse my layman approach, but when i turn key in ON position, there is a sensor that clicks erractically that is screwed into throttle body. i took it out and it is "plunger " with a spring. i sprayed it good with throttle cleaner but i still here clicking.. Is it normal to click ? what is this sensor called ?

the plunger does not move in or out with key on or off

appears to IAC.. i cannot push it in or out by hand

Car runs fine with MAF disconnected. Chugs and dies when plugged bk in. Yay
for all the help here.