1985 gmc sierra 1500 4x4 stalling out and starting issues.

[jason]

I have had my 85 sierra for 3 months now and still new to the forum.

It was running fine (In canada) so cold starts were not an issue neither was idling.  Right now, however, the vehicle will run just fine for around 20 minutes.. then when I press the gas pedal down... the engine will bog down and make the sound

chop chop chop chop chop... before the engine picks up speed and begins pulling again and sounding fine.  (the chop chop sound is not metal on metal).  It has oil.  While its bogging down i get almost NO POWER until the engine picks up again and resumes somewhat normal operation.

Also... especially on hills the vehicle will try to stall out.  Any kind of incline causes the vehicle to eventually hesitate and then it requires putting my foot to the floor to get the vehicle to go up.

the engine will eventually pick up and resume running strong.  Then out of the blue the vehicle stalls out and i'm there on the side of the road starting it with my foot on the throttle to get it started.. then it runs  the rest of the day A OK.

Now.. this morning... i try to start it and it just dies every time.

I'm going to be heading over to the parts store to begin with the following: fuel filter, air filter, pcv valve, and oil pressure switch.  (the choke light is on) and i am pretty sure its the oil pressure switch.. but that requires the distributor to come out to access.

Could a bad or inoperative choke cause the symptoms I've described?   I've just ordered two books on carb rebuilding to read through if that is my only recourse on this.

Thanks for reading!

Jason.

[Lit549]

Sounds like trash in the carb(or tank). BUT,ive also had a truck do the same crap and it was the batteey,yes a bad battery..Ignition or coil maybe could do that but usually if coil is bad they just quit..Id def start with fuel/carb..How about soot in exhaust pipe?? Alot of black?

[Fairlane514]

You don't need to pull the distributor to change the oil pressure switch. The one you are looking for is on the driver's side of the block near the back just below the cylinder head.

Fuel pump may be weak. Could be junk in the needle/seat of the carburetor not allowing enough fuel into the bowl.

When the engine is cold open the hood take the air cleaner off and move the carburetor linkage to set the choke, it should snap shut. You can then turn the key to the "on" position and see if you have power to the wire connected to the choke(use a test light).  If not you may have to start the engine so the oil pressure switch allows power to the choke wire. If you get power to the choke wire watch it and see if the choke starts to open. 
if you never get power to the choke, then it will always be choked and run crappy/rich.

[Fairlane514]

I forgot to add. There is a fuse (20amp) at the top of the fuse block that controls the choke light and power. Check and see if its blown.

Its the one closest to the kick panel area and at the top of the block right next to another 20 amp fuse.