Fuel pump turn on when key in "on" position?

Does anyone know if the fuel pump turns on when you turn the key to "on" (aka the vents, and other electronics begin to run)? Sometimes I get a stumbly startup but it's rare. Thinking maybe if I let the fuel pump "prime" that it could alleviate this issue.

Thanks!

 

I just noticed something like that the other morning on mine as well. I'm not sure if the key turned to on primes the gas lines or not. I assumed it did, just based on past experience with other vehicles.

 

As I understand it....the fuel pump starts when the starter is engaged to start the engine. No priming. Part of the reason the engine requires multiple turn overs before starting. My truck turns over a minimum of 3 times before the engine starts. Always been that way.

 

In my experience with vehicles, all were FI and not carbureted, the fuel pumps kick on in 'on' position before starter engagement. To, yes, prime the fuel system to turn over.

Not chastising, but is this your first vehicle?

 

It will come on when the key is in the on position, you can probably hear it running

 

"On" will not start the pump.
"Start" will start the pump but it will not maintain it when key returns to "on".
The crank sensor signal (V6) will maintain the pump on, cam sensor on the 4 cyls.
The cam/crank signal will initiate and maintain pump operation without the starter (STA) signal at all, as in push starting a manual trans truck (key on).

 

No one believes me when I tell them this. It always "buh muh uther cars never done this", if all people wanted was confirmation of their incorrect assumptions why not hire a yes man. End rant, good info as always @Dirty Pool

 

I know, I should have this diagram on speed dial by now.
Even though it seems to imply both crank and start are needed together to start the pump, not the case.

 

Thanks a bunch. I won't be wasting my time with leaving it on the "on" position for a couple of seconds then

 

The 5VZ commonly has soft starts (where one or two cyls fire and then the rest catch on) when hot and longer cranking when cold, just the nature of the beast. The 3RZ starts very quickly if it is a distributor model (cam sensor is different in those) but is a bit longer like the 5VZ in the later years.

 

Any insight on my condition? https://www.tacomaworld.com/threads/04-3-4-starting-issues-fuel-problem.476842/

 

It took me a while to realize this. The 2000 S10 I had primed when the key was turned to the on position. I could hear the pump when I turned the key on. Almost instant start up.
My Taco takes several rotations . At first i thought there was a problem, then found out it doesn't prime. My Honda accord doesn't prime, either.

 

I would first verify if the pump is actually running. If it is you will need to start doing some circuit testing. I doubt it is but stranger thing have happened.
The more likely scenario is leakage in one or more injectors. The fuel system is pressurized when running and "should" hold most of that pressure for a few hours when shut off, even over night in a really tight system. Try shutting her off for the "ten minutes" or so with the key off and see if you get the same symptoms. If the flooded condition persists then the injectors would be suspect.
Keep in mind that the fuel from leaky injectors will eventually bleed off the residual pressure and stop leaking. After some time (hours) this leaked fuel will dissipate with a subsequent start appearing more normal.

 

Thank you!

 

it is my understanding that the fuel pressure regulator should hold the fuel pressure in the fuel rail. take the vacuum line off and see if there is gasoline there, if so, it is bad.

 

I recently was having a problem with mine not going off in the on position... Still not solved. As I came to understand it the pump engages for 5 seconds or so then shuts off again.

 

It shouldn't turn on. You may have a bad circuit open relay. (stuck in the on position) or ECU. Or someone has jacked the wiring

 

Hey man so your saying that my 1996 Toyota Tacoma will not prime the pump with kep on only when it's starting

 

Yes, the engine has to be turning over either by the starter or running.

The cam signal for the 4 cyl… I did not know that.

 

It does for a few seconds then shuts off until you crank it. Basically pressurizing the fuel system.