90 4.0.... ok long story....had bad sending unit (ran out of fuel showing 1/4 tank) had to replace pump too. first pump replacement wouldnt pump up to pressure, second replacement just quit so i put in the original to take my chances on the gauge. next trip alternator dies. replaced alternator...next trip battery went dead (my own fault, left radio on too long with engine off) go a jump start. on the way home it just died. pump not comin on. towed it home recharged battery. pump still wont come on. took pump out put 12volts to it and it works. no power to it. checked and then jumped past relay. still no power. bypassed ballast resistor. no power still. no power to ballast resistor. ive started tracing wires. any other ideas?

 

anyone have a wiring diagram for a 90?

 

ran power to the pump and put it on a switch and it wont start. pump does run and it has pressure. now what? im going to check for spark now. im desperate this a daily driver. where else can i look?

 

this might shed some lighthttp://www.pirate4x4.com/tech/billav...ion_manual.pdf

 

havbe you checked for ground at the ple for the pump

 

i have tried to find all the grounds and freshen them. i cant understand why the pump wont come on with the key in the on pos. but does in the start pos. i read that in crank pos.the ballast is bypassed but i have bypassed it also with no luck.

 

pump only runs for a couple of seconds when you first turn the key on its not doing that

 

Freegdr is right. When in "on" position pump primes and then the ground is taken away. Pump gets power 4 different ways. when key is on, when cranking, when running and at wide open throttle.

 

the pump doesnt come on for the 3 sec at the first key turn. only at crank. i worked on it all day tracing wires and gave up. i read somewher also if there is no spark it wont pump but it should still have the 3 sec at first key turn i think.....im starting to lean towards the ecu

 

I would check for battery voltage at the pump plug. Get a girl friend to turn the key while you check the plug for voltage. IF you have voltage it's mote than likely the pump. If not I'd start at the fuse box, you've probably toasted the fuel pump relay fuse.

 

update..... i have no spark either. no power at fuel pump plug unless cranking.

 

problem solved!!! ecu exchanged with a doner and its alive!!!! thanks for all your help! the links helped made a difference.

 

Congrats on solving your problem!