ive noticed on 2 of my trucks that ive replaced the fuel pumps on and the gas gauge does a little bouncing around when its under full. is it cause of it being a non delco pump or just a coincadence that the sending unit is beginning to crap out?

 

probably a cheap sender...OR..sometimes on older trucks with metal gas tanks...they have plastic baffles in em..these baffles are known to come loose after a few years and float around in there like a submarine.it can hit the sender,sending the gauge nuts,or just let the gas slosh so much more.
its really fun to figure out..lol

 

i know on the other truck that did this i looked in the gas tank before getting rid of it and the baffles were still in tact. as far as the sending units go they are still the factory sending units just a direct pump replacement thats why i was wondering if it could be the sending unit getting a little old.

 

most likely,yes....there is only 1 way to know for sure...unplug the sender and vary the resistance on the purple wire while watching the gauge....fun

 

so would i put different resistors into the purple wire of the plug to do this?

 

yep..or..find another sender..plug it in and work the float

 

is it easy to find a delco sending unit reasonably priced?

 

nope..lol...i put 1 in my truck a few years back..they're about 200..without a pump