Rough idle after installing new fuel pump

[Overthedge21]

87 k10, 350 TBI. I don't know if it matters, but the VIN codes for a 305, prev owner speapped in a 350. Anyway, after my fuel pump finally went yesterday, I replaced the fuel pump relay and the pump. Now the truck idles like it's running on alcohol, but once I get on the gas and start driving it evens out. I got home, and when I put it in park it was now idling fine. Go inside only to realize I had to move because I had parked in the wrong spot, and when I stared the thing back up it was idling rough again after sitting for less than a minute. Just put in a new o2 sensor as well. Any ideas why it might be running like this? Also, the pump I put in was for a 305, I was told it's the same pump as they use for the 350 so I went with it. Is there actually a difference? Or is something else bad

 

[Rusty Nail]

Fuel filter

 

[Overthedge21]

But then wouldn't it run like crap no matter the rpm?

 

[1987 GMC Jimmy]

Not necessarily. It would be a good idea to go ahead and change it out. They sometimes have them at the TLE counter at Walmart for like three bucks, and Autozone has them for like five. The pumps operate at the same pressure for SBC's and earlier BBC's, about 13 PSI. The only one that's higher pressure is a late TBI 454 pump at about 30 PSI. Are you getting any trouble codes with it? When you take your filter off, I'd borrow a fuel pressure test kit from Autozone and tee it in there and make sure your pressure is okay since you did just have the pump changed. Did it run better before?

 

[Overthedge21]

After having some help and cleaning out the fuel filter, it appears the issue may have been one injector spraying less fuel than the other. Messing with the lines by the tank so much must've stirred up some crap and sent it into the injectors.

 

[Rusty Nail]

Well,

 

[Overthedge21]

Would crossing the fuel return and vapor return lines in the sending unit cause this?

 

[Rusty Nail]

Thats probably not possible if such things even exist.

 

[Overthedge21]

It does exist on mine, the sending unit has 3 lines. The fuel supply from the pump, the vapor return from the catch can, and the fuel return from the throttle body for when the pressure regulator opens to maintain a certain pressure and not overpressureize anything

 

[Rusty Nail]

My fuel pump has two outlets! , I guess i've seen it all now!

 

[Overthedge21]

You have a carb right?