So I bought an 85 K5 last month. When gas tank got to a half tank it started running rough. I filled up ran like a champ... well got to half tank and again running like crapola. So I replaced filter in carb. There are no in line filters. I am back to a full tank. So dropping the tank would be a PITA. It will not stay running without pedaling. If I drive it will bog and die. It's hit or miss.... If I stomp on it..... it will stutter the pickup quick then bog down and stutter again.... I think it may be a gas issue. I put a bottle of heet in tank for moisture no help..... Is there some type of filter in the tank? What would you suggest?

 

diffinitly sounds like a fuel delivery problem! Does it do this hot or cold or if you run it from full to half non stop does it do this? Is it popping like its lean or is it act like its loading up and dying? Just trying to give you a better diagnosis!!

 

When it's cold I have to pedal it for a min or so to keep it running. Once it warms up it will idle low... as soon as I go to drive it will try to die unless I start the pedal tapping .... I recently bought so I was throwing tank fill up out there. Since last fill up it's still acting up. Not too sure about running lean.... If I push pedal in steady it will die. Like it's either loading up or running dry. I'm no mechanic, I know it's hard to understand my explanations.

 

Your fuel pump should be mounted to the engine on the front passenger corner. You could be experiencing a weak pump. The lower the fuel level in the tank, the harder the pump has to work to get that fuel out. Or, you may be experiencing a problem with the pickup tube inside the tank. If the pickup tube had a hole in it, it would cause the pump to suck air whenever the fuel level drops below the hole.

The pump is easy enough to change out and at a typical price of $15-$20, it won't be hard on the wallet either. This would be the first step I would take.

Here is an image I took from the engine out of my Chevelle for someone else quite a while ago. It shows the pump, how it's mounted, and the pump push rod retaining bolt location (where applicable).

 

Thanks, Do you know the bolt size of the top of your head? I will change this weekend and update...

 

Which bolt? The one in the front? If so, just take one of the two bolts that hold the pump on and use that. They are long enough to get in there and retain the pump push rod. Hand tight is good enough. It just has to hold it well enough that gravity doesn't let it drop down into the lower cavity.

IIRC, you'll need a 9/16" wrench. Having a liner wrench helps get the fuel line off the pressure side of the pump (what runs up to the carb).

 

LOL I did not mean "of your head" OFF.
Great thanks for the update.




Hand tight does not work So I turned the long bolt with wrench two turns and the rod was still loose. No connection, so I backed the bolt out and it was really tight. I hate to force it. Would you suggest keep going until it touches?

Thanks again

 

Bare with me...Got the new pump today. It has two input lines. The old one only had one. BUT.... There was another smaller tube just hanging by the frame. Return line I suppose... The word "in" is in between the smaller input line and the output line to the carb. The big input line (same size as old fuel pump) beside it. I put the small return line on the smaller input 1/4 (which said IN) and the bigger input line with the bigger hose (the hose i removed from the old pump). Truck runs the same.... should I try swapping those hoses first?

 

Sounds like you have it installed correctly, but it's worth a try at switching the lines. Did the new pump come with anything stating the function of each port?

 

of course not