94 gmc jimmy...fuel pump relay?


#1

hi all, my jimmy died on me yesterday on my way home from work…
i thought the fuel pump went because i couldn’t hear it when trying to restart…
i had about a quarter tank of regular in there,put in 2 gallons of super and it started, but died again
about a quarter mile down the road…
got it home with a push…
after searching for and checking any fuses i could find…
swapped relays on firewall and all seemed well…i heard the pump and it fired right up…
went walked, just in case) and got another relay, and now i don’t hear the pump again,
the battery is a bit low now,so maybe a jump would give me enough juice?
i’m going to jumper the wires/relay…and be sure the pump is working…i’m sure it is…
94 jimmy 4.3 vortec 140k
thanks for any help i gotta pick up my wife from work later and don’t want to get stuck again…


#2

ok, i removed the relay and jumpered it…gray and orange…
fired right up…ran a few minutes and cut out…
went back to relay…nothing…
back to jumper, fired up and ran again for a few minutes 'til i closed the passenger door!???
started her again, no problem…moved to my usual parking spot, still running…
get out and close the drivers door and she cuts out…
i’m really at a loss here…i suppose i’m good enough to get the wife from work (5 miles)
but i gotta solve this…i can’t go around installing/removing this jumper for long…
so i’m thinking ALL the relays are bad/or the problem lies deeper…hopefully not the pump itself…when she’s running, i hear the pump and there’s no signs of irregularity or change in tone…
please help…i gotta get this solved before the rain…and certainly before monday morning!
thanks for any help and or insight!


#3

I don’t know whether this will sound odd or not, but try running it for a while with the gas cap off and see if it keeps running.

Ideally you would also get a fuel pressure gauge on it and watch what the pressure is doing.


#4

i’m going to change the filter, then see where that gets me, i hate to buy a tool i’ll rarely use…but i will if i must…i’m sure the info it may provide will be worth it in the long run.
if it runs longer on it’s own without the cap, what does that tell me?


#5

Sorry but I think you’ve got a bum fuel pump. They can be very intermittent. Even if the relay was bad which I doubt, there should be a secondary circuit through the oil pressure switch that keeps it going once there is oil pressure. You’d just have to look at a schematic to see for sure.


#6

On the gas cap thing - most tanks have a vent valve on them that allows air to move in to replace the fuel as it goes down. If it gets stopped up and air can’t get in you basically end up with a vacuum in the tank and it becomes really hard to pump the fuel. The poor little fuel pump ends up trying to collapse the sides of the tank.

On a fuel pressure gauge - I own a basic one that I got for $40. I don’t have to use it often. But I’m very glad to own it. Anytime anything funny happens with one of my cars its very handy to slap on there & check for a fuel pressure problem. So I don’t use it much. But it surely can save a lot of time & aggravation when you have a problem.


#7

ok, sunday morning!
i put the relay back in and she started right up…with some movement of the relay, she died…pulled relay and put in another one, and she starts up…again with movement she dies. swap in another relay, secure them in their bracket there…she started up and has been idling for 25 mins. so far with no issues…doors open and closed, softly and more forcefully…still she idles fine…i’m stumped…there’s gotta be a loose wire somewhere…perhaps above the tank? not sure if i can get a good enough look or even a long enough arm to know for sure…
and still afraid to drive anywhere…


#8

my wifes blazer acted the same way. it was the fuel pump.


#9

It sounds like the source of the problem is where the relay plugs in. Clean the connection point.


#10

Get a test light probe at least so you can verify that power is getting to the pump when the trouble happens. If the pump has power and it isn’t working then it needs to be replaced. If there is a bad connection to the pump the tester will show you where it is at by placing it at various test points on the circuit.