hot wires=no lift pump pressure

[cranknrods]

ok-heres the deal. i can get in and start the truck in the morning and it runs just great but then it stops getting fuel and dies. let it sit for a minute and it a start right up and run alittle bit then die -on and on like this and every time i start it, the dang thang will run for a little less time then the time before. when it dies and i turn the key i dont hear the lift pump coming on anymore. the lift pump has been changed 3 times cause i keep thinking i got a bad one-the last one was a GM pump-so its not the pump-someting in the wireing to the pump is getting hot and not sending volts to the LP . and i just put in a new pump relay and thats not it. any ideas-its not the PMD either. is their a pressure sensor in the line some place telling the pump to turn on and off as needed or maybe another relay or something. its really hard to trace the fault cause it only happens when the wires are hot and by the time i get under the truck to find the electrical fault i only got about 5 min's before it cools and starts sending volts again. please help-im tearing my hair out
thanks for the replies any and all ideas are greatly appreciated.
thanx

 

[towcat]

I know you have the "borg" style Ip and I can't guess if its even related to that or not. But most GM's with a electric pump have the oil pressure switch as the cut-off. if you have a three prong oil pressure switch, one of the terminals definitely is it. just for gp, change it out, the part isn't much $$$ at all. should be under $20.

 

[dieseldummy]

IIRC, the newer models with the DS4 IP control the lift pump via the ECM.

 

[glow-plug]

When it stalls do the dash lights come on (WTS, Check engine, etc.)?

The LP only runs to for a short time to prime the system when not running.

I change my ignition switch because of stalling and that was after a new FSD.

So far so good, found the contacts inside the old ignition switch were burnt.

 

[Dave Barbieri]

CR -

Did you ever figure out the 'hot wire' problem? (inquiring minds wanna know....)