2 fuel pumps, in-tank bad? how do u know?
I have an 1987 4x4 ranger, 2.9 6cyl. 67K miles on 2nd engine, I bought it used for $450 & it runs fine until it is warmed up & then in any gear, exactly 2300 rpm's & up it runs like it is mis-firing, chugging, & loses power. I put on a new fuel filter, plugs,rotor & cap (old cap was really ozoned-up), checked all vacuume lines, put another "rail-mounted" fuel pump on, checked the coolant-temp sensor(ok -above the thermostat), checked the reading on the throttle control (with a voltmeter,6-9 & works) the EGR works good (cold has a good idle) I know this truck has another pump in the tank (sending-unit) . is this a "supplemental" pump for higher rpm's? this truck starts on a snap-of-the-finger & idles fine, does anyone have an idea? I am thinking it's something to do with the distributor/sensor (temp related?) or maybe that in-tank fuel pump. anyone??? I didnt see any other posts on this subject & i havent tried the "hammer the tank" method to check for a bad pump.
I only own Fords & have never dealt with something like this.