Fuel pump priming issue

Ok, so I have a 2006 Tacoma that is having a rough start after it sits for anything over about 12 hours. I’ve came to the conclusion that my fuel pump isn’t priming when I turn the key to run. (I replaced said fuel pump maybe a few hundred miles ago after a stutter while driving at high RPM which corrected that issue). The red light under the stereo is going away when I insert the key✅ I’ve swapped horn relay and efi relay around with c/open relay to see if it was a bad relay✅. I’ve tested the voltage at the c/open relay with a jumper and verified that my pump is working.✅. Although it is not priming, I’ve found that when the engine is cranking the fuel pump engages and eventually builds enough fuel pressure to start the engine and continues to run. (I guess I could manually prime the fuel line by holding a jumper where the c/open relay goes for a few seconds when it has this issue, but would rather have it working properly lol) After idling/running, it will still not prime but seems to have maintained enough pressure in the fuel line to start up pretty quick. The only way I’ve been able to get the prime function to engage is by after letting it idle for a while, I’ll turn it off; start the truck and shut it off quickly; turn the key back to run and will finally hear the pump turn on for a few seconds (prime) as it should. What signal is my ECM not receiving that should be telling my fuel system that it needs to be primed after the fuel pressure bleeds off after sitting? Or am I missing something obvious? Thanks for any advice in advance. -Joe

 

Toyota doesn't use a key on prime, the fuel pump only runs during cranking and after the engine has started.

Sounds like your fuel pressure is bleeding off when it sits for a bit, could be a bad regulator, bad fuel pump check valve, or leaking injector.
You need to have a fuel pressure gauge teed in to confirm and then figure out where it's leaking by at.

 

I was going to say it sounds like the pump's the check valve also, I suspect the pump can't pass the sustain pressure after key off test. I'd slap a FP gauge on it and do some testing.

 

Ok so how often is the the fuel system supposed to engage when you turn the key to run, before crank? Because I have seen it get the voltage at the c/open and can hear the pump turn on for a few seconds before trying to turn the engine over but only once in a while.

 

Do you have a fuel pressure gauge? Are you just going by sound?

 

I am just going by sound and voltage reading I do not have a pressure gauge but it sounds like I’m going to need one haha. When I do hear it turn on for a few seconds though it starts up easy

 

I've yet to see a Toyota that does any sort of key on prime, the pump only runs when the ECM sees a crank request from the Ignition Switch on the STA circuit and when it sees a RPM signal from the Crankshaft Position Sensor.

 

Ok I’m convinced that there isn’t supposed to be a key on prime . What are the best points to check with a fuel pressure gauge to cross my regulator, check valve, and injectors off the list ?

 

Welcome to TW...What kind of Fuel Pump did you put in it?

 

It was from carparts.com
Part number REPT314520
It runs good but could something with the fuel pump cause it to bleed off while sitting?

 

I would bet on the pressure regulator at the end of the fuel rail moreso than a defective new fuel pump.