Another fuel pressure issue

[tdunks88]

So for the life of me I cannot find any information on my exact issue. I have a 2016 Tahoe, bought from auction so I don’t have much knowledge of previous work done. From the day I bought it, it has had a long crank after sitting (2-4) seconds depending. Figured it was the fuel pump but before I replaced it I would do some testing. Pressure is all good (roughly 50psi) when idling, and no other issues while driving or codes. Did some more digging and found that when I hit the push to start button, I don’t hear the fuel pump nor does it build pressure. Only when it begins to crank it builds pressure. I found if it put it in accessory mode (hold push start down for 5-6 seconds) the fuel pump kicks on and shoots up to 80psi within a few seconds. Then fires right up. System seems to hold pressure just fine. But the ECU doesn’t want to tell the pump to prime on the start up sequence. FPCM has been replaced and grounds were all checked. I am lost at this point except to replace the pump if I need to. Any suggestions? Thanks

 

[LsHart]

Auctions are scary. Never know what u are buying. But DVOM is needed and someone that works for the circus to get to the fuel pump. And or pigtail connector . Find fuel pump relay and check which one is key on hot and test it both ways on start up. See if power is going to the pump when triggered to start. That will always point u in the right direction. Also check for corrosion. Use WD40. Will help u verify pump. Is there not a filter?

 

[Fless]

Don't these have the low pressure fuel pump in the tank, and the high pressure fuel pump on the engine?

A good bidirectional scanner should show you both of the fuel pressure readings. Document them before starting, and after to see if it's a possible cause.