died and wont stay running...

[ERIC87442]

so this is a gbody buuuut i need help, i got an 02 chevy silverado with a 5.3 and i was driving it and it just died, i turn it to the on position and my fuel pump sounds very weird and bubbly and if i start it it idles really low and dies, in the time the fuel pump sounds very bubbly and gergaly while it is running also, if i press in the shrader valve for the fuel rail it sperts out some fuel but doesnt rush out. im thinking its maybe the fuel pump but i thought they just went out when they died... i disconnected my mass air flow sensor and it would idle a little better, i have a reader that shows me the information of the sensors and it shows my mass air flow sensor is reading when i have it hooked up and doesnt throw a code unless i unhook it obviously, but i was wondering, fuel pump? mass air flow sensor, or something i may be overlooking??

this is my only means of transportation the trans is out of my 442 😢

 

[megaladon6]

do a pressure test of the fuel pressure. IIRC it should be 55lbs and the chevy's can be very sensitive to low pressure, even at 45lbs! fuel pumps USUALLY just die, but not always. they can even deliver proper pressure but low volume. if pressure comes in correct, chart the MAF data. slowly get as many RPM's as you can, then try it quickly.
do you know the idle MAF reading itself?
also, use the reader to check for misfires. and see what the O2 sensor is reading and if it's fluctuating or steady.

 

[monte olrac]

I've seen idle air control valve cause that problem also so you might want to check that also

 

[ERIC87442]

i wasnt geting any miss fires but i can do it all again an check what my mass airflow is reading and my o2s are reading, ill go do it and freeze frame it and ill put down all the readings im getin, my big thing is it gurgles like crazy from the pump when it does run

 

[ERIC87442]

ok keep in mind engine is cold. this is what i got when it was runnin till it died, frame -5 it started at maf flow g/sec 8.17 rpms 690 short term fuel trim 1 at 32% as well as short term fuel trim 2 02 sensor 1,1 .375v 02 sensor 1,2 .175v o2 sensor 2,1 .100v o2 sensor 2,2 .155

frame 0 st fueltrim1 32% stfueltrim2 31% o2 1,1 .755v 02 1,2 .830v o2 2,1 .105v o2 2,2 .180

and frame 6 about the time it started running rough. maf 7.98 rpms 691 st fueltrim 1 43% st fuel trim 2 42% 02 1-1 .075 02 1-2 .120 o2 2-1 .120 o2 2-2 .155

frame 8 1 frame from when it died rpms are 145 maf 8.24 all fuel trims are at 0 all 02s are .090 or lower

all long term fuel trims for each frame was at -1%

 

[anakputa]

Unplug the MAF and see if it stays running. Then do a fuel pressure check.

 

[ERIC87442]

if i unplug the maf it will run but like sh*t haha, but i did a pressure test i got about 20-25 psi... should be 55-65ish so im really thinking the fuel pump is messed up, i just put a new fuel filter in it the other day so thats not the issue haha. the pump was kind of louder for a while before this happened too

 

[anakputa]

Time to drop the tank..Also check the electrical connector and the ground while your at it. Seen a few connectors melted causing the pump not to get a full 12Volts.

 

[ERIC87442]

i put a new pump in and now its fine 😀 thanks for the input everyone

 

[megaladon6]

great!
just in case anyone reads this down the road, with a similar problem----going by your freeze frame date (IIRC) you're running lean, but the MAF is right around where it should be, and the ECM is doing what it can to correct the A/F ratio.
the fuel pressure is definitely low, as you said it should be around 50psi.