1990 Silverado problem

[austinmike]

1990 Chevy Silverado Z 71 5.7 Been sitting for nine years we put a new fuel tank in new fuel pump and fuel filter a new battery new gas it starts up and dies unless you press the gas Pedal... Anybody got any ideas what it could be

[Tyrex750]

Mabye throttle position sensor, are the efi is clogged up

[JTRichardson]

sounds like its not getting air

[Kingfisher789]

Which injection system? TBI or spider injection? tBi you can buy injectors from rockauto?

[austinmike]

It's a tbi

[Clay6x45]

The original fuel pumps/senders were notoriously bad and unfortunately many of the replacements are as well. I hate to say but you may have gotten a bad replacement. Anytime you replace a fuel pump on these old trucks remove the bed and cut a replacement window in the bed. There is an aftermarket plate that bolts in so future repairs are a simple plate removal.
Rent a pressure tester to see if current pump is working.

[PYBUCK]

It's a tbi

Out a new one on or rebuild it and it will run ok.

[Strummer]

Did you replace all the fuel lines too ?

[Kingfisher789]

It's a tbi

Take the air cleaner off and watch the injectors spray. 9 years? They are toast I promise you

[austinmike]

Ok going to try the injectors thank you all

[Big Lee]

Idle air control motor is stuck. It is mounted in the throttle body. Take some carb cleaner and spray it out. Should start working again

[RifleBowPistol]

I would get some good carb cleaner and spray the throttle blades down good. Spray the IAC, you can remove it and clean it and the bore and valve seat for the IAC. I would clean the throttle bore, open the throttle blades and clean all the way around the throttle blades, top side, bottom side, till the blades are nice an clean. Then get a gasket kit and or a fuel pressure regulator. Then something like Seafoam. Pull the top of the throttle body off, clean all of it out, replace the fuel pressure regulator. Then pull the injectors, spray them down good, mainly the top side where the fuel comes in, there should be a screen, to keep out larger particles. Likely there is some fuel that has gelled up in the top of the injectors. Spray them down good, then soak them over night, in Seafoam or Berryman's Chemtool. Then replace the O-rings down below the injectors, replace all of the gaskets for the throttle body, as you put it back together. That should help out a lot, if not completely fix the problem.

The fuel we have been getting for years, will gel up, or form yellow chunks, or white powdery corrosion, when it sits and dries out. Also when rubber components like fuel pressure regulators are subjected to modern fuels, then are allowed to dry out, the rubber will crack, causing a leak. If a fuel pressure regulator diaphragm cracks, it will leak fuel to the side of the diaphragm, that is supposed to see vacuum. Which is connected someway to the intake manifold. So if the diaphragm cracks, it will leak fuel into the intake manifold, and the same time, since the vacuum is not able to pull the fuel pressure regulator valve off it's seat, the fuel pressure will be high, like when at WOT. So it will run doubly rich.

I would go through that whole throttle body. Taking it off and going through it off the engine will be a lot easier. At that point you should just replace the gasket under the throttle body while it is off.

[austinmike]

It was the injectors thank you all for the help

[kingranch]

im a pro now w these pumps.. i can have the bed up and off in like 20 mins. just a few bolts underneath..

You can even loosen one side and remove the tank side bolts and lean bed

[savage1134]

set the parking brake, keep it running and let the system relearn base idle.