1991 geo tracker doesn't usually start in colder weather.

[fixkick]

the pump is bad or the 2 wires supplying power it is bad, connectors top list
you can swap the Main relay with the fuel pump relay
below the ECU are 2 identical relays.
one is green socket with pink wires , other is main, for ecu
you can swap this at any time, they are identical.
if the ECU goes dead after we now know (and CEL lamp dead too) then the main relay is now known to be bad.
when the pump is dead.
go back to the tank, get a nice rubber mallet or 18 " 2x4 board and hit the tank bam, if that makes the pump wake , the pump is bad or the 2 wires to it are bad. (on top would be it)

here are the 2 relays,



this can be tested with a voltmeter when dead.
see that pink wire there,?''

i like to cheat (US navy ways) we go to the middle first , making the job 1/2 less. see?
the tail light left SIDE is that place but takes 2 people, (the 3 second rule , makes that so)
same wire pink
as seen on my pump page and here , largest pink wire with black strip is the wire.





the wire runs from the relay,
under the drivers sill plate, to the Leftrear tail lamp then from there down to the bumper, jack then up and forward center to tank and one more connector to fail.
that is the actual path, (in my 91 inspected every inches of it looking for hacks ,damage , and all connectors in the path at least 4 there are and all connectors were bright shinny brass, and no green rust on them (corrosion not allowed) all the way to the tank.
if it failed I use voltmeter to find it.
but it is a fact, takes 2 people you and kid or any one safe at the key, 10 year old kid? put 4dw lever in Neutral, chock wheels, car can not move and is safe.
i then ground the meter black test lead to the body. or (battery neg lug)
with meter on DC volts, prob the large pink wire, end to end, obviously the most easy points first, and the relay tops that list.
if it goes to 11.5 to 12.5 volts key to start, then its good. (will be lower cranking, but that is only if it cranks, its not, 10v is possible cranking.,
Then to tail, lamp huge plug pink 12v key on, each time. (11 to 12v range, in truth no less than 0.5v below actual battery volts is spec)
here



make sure G402 is not bad , 0v key on each time its ground there. to the pump ,clean it . (all 2 door cars LOVE TO FAIL here G402 and the pink connector pins on the left ) water gets up here and well, fails.
http://www.fixkick.com/INJECTORS/PUMP/Pump-Ground1.jpg
Next is center here of bumper bundle of pump wires.

here is the real drawing,

see this. see c403 is where the huge pink wire is.
see rear brace here and this bundle of wires it too can fail.



then last the pump. connectors. this connector too can fail., and is super hard to reach.



all this is on my pump page, lots of info there and tons of causes. i think not one failure mode missing.

Fuel pump relay bad, (rare) do the swap
wires bad
connectors bad
pump bad (smack it hard, keep this in you head so if stranded, pump dead, smack it , no tow truck. )
G402 bad.

http://www.fixkick.com/INJECTORS/PUMP/dead-pump.html