1993 gmc sierra sometimes the pump doesn't turn on

Asked by Sanchez Aug 16, 2020 at 10:21 PM about the 1993 GMC Sierra 1500 C1500 SLE Extended Cab Stepside SB

Question type: Maintenance & Repair

How's it going hope everyone is good .I'm trying to see if I
can get help on my truck 5.7 .ok so I have been having
trouble with my fuel pump not turning on sometimes for
about 2 months.the first time it sputters on me going 60
but never again and went away immediately but when I got
home I turned it of then it didn't turn back on and I didn't
here the pump run so I figured no power .went to AutoZone
and got a fuel relay truck started right up.2 weeks later did
the same thing so I exchanged the relay and the first crank
didn't start but after 2 minutes started and lasted another
couple of weeks.so this week it would sometimes not turn
on then later I would try again and started .today it doesn't
want to start even with new relay.the first and second time
it happen my oil pressure gauge was going crazy so I
changed it in case that had something to do with it.but
today when I crank the truck oil gauge doesn't move while
cranking .is it supposed to move or only moves once truck
is turned on.i checked wired under gas tank to pump and
grey wire is getting 12v purple wire to gauge 8.5 so could it
be the pump its only 1.5 years old .how can I give power to
pump to see if it kicks on .I just went outside and it turned
on again but with a ticking noise that went away and don't
know what it was.only thing I did was cleaned the ground
from thermostat housing but it didn't turn on after I did that
.i cleaned the ground to chasis also few days ago so that's
not it.does anyone know where the black and white stripe
wire from fuel pump connector goes . It's so weird that only
problems I'm having is turning on and not while driving like
if something gets hot and then stops working

2 Answers

59,735

I think I would get a repair manual as there could be many things to test to rule out the issue, one thing that after it gets hot may not work is pick up coil inside distributor and may work fine later when cooled off but this is just one symptom, may fail with no symptoms so may not be your issue. As far as the pump being 1 1/2 yrs old, if it was replaced with cheap after market pump (pump only kits), some make it to 2 1/2 yrs old, best to use genuine GM parts & full sending unit replacement. I would test for spark while its not cranking, may be a ICM or any of the wires/systems that the ICM reads to tell the fuel pump to turn on could be the issue. The repair manual will tell you what wire is what and how to test it and its voltage.

I have a new distributor so it's not the pick up coil that would make my tuck die out all of a sudden which I thought was the fuel pump that's why I replaced it .it's a new icm that came with distributor but I only paid 45 so it might go fast but I don't know if it has anything to do with fuel pump

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