Stalling problem 2009 6 cylinder

I bought it new in 2009, 116,000 miles on it now, garage kept, lovingly maintained.
The other day, for the first time ever, I started it up and it ran for three seconds and stalled. It would not start again. Battery seemed okay, starter was singing like mad. Voltage measure 13.2 VDC. Called for a tow, he put it up on the flatbed, took out a box with cables on it and clamped them to the battery. Not sure what it was, but it was not heavy, very lightweight. He looked at some LEDs on it, seemed confused. He said “let’s see if it will start” and of course it started right up. We left it running while we drove home. He backed it down off of the flatbed, and shut it off, and it started right back up. Voltage while running was about 13.6 VDC. Battery was only 3.5 years old. I replaced the battery with a brand new one right then. Truck has started right up every time since, but I wonder.
Does the fuel rail have a pressure sensor that causes the fuel pump to cycle ON and OFF?
Or just a pressure regulator and the pump runs continuously? I ordered a new fuel pump relay, but I wonder if the pressure sensor or regulator or fuel pump is going bad.
Or is my problem electronic ?
I plugged in my scanner into the OBD port before I replaced the battery, but it showed no codes.
Spark plugs are three months old.

 

Sounds like you have kept up on & are willing to do maintenance ahead of schedule which is good. Unfortunately nothing we can tell you other than anecdotal stories or wild guesses. For a definitive answer you'd have to test it while the problem is occurring for things like fuel and spark. One thing you can double-check in the meantime is that all your grounds are good, could be something that simple (or not, like I said no way for us to tell, but it's something easy to do for peace of mind). Good luck, Merry Xmas!

 

Does the fuel rail have a pressure sensor that causes the fuel pump to cycle ON and OFF?
Or just a pressure regulator and the pump runs continuously? I ordered a new fuel pump relay, but I wonder if the pressure sensor or regulator or fuel pump is going bad.

 

The fuel pump uses a resistor to operate low speed. When the truck first starts, it operates on high speed for about 3 seconds. Then defaults back to low through the resistor. The resistor is operated by the relay.

Is the resistor or the relay your issue?
I don’t know. Maybe. Or it may be neither one.

I’m just posting how the system works.

 

Where is the resistor located on a 2009 Tacoma?

 

Down in front of the battery.

Looks like this.

 

Thank you for showing me this.
Does the fuel rail have a pressure sensor? Or does the pump run all of the time, using a pressure regulator with a return line?

 

Yes it runs all the time the engine is running and dumps overflow back to the fuel tank.


Tank >> Filter >> Pump >> Fuel delivery tubing >> Fuel Rail >> Fuel Rail Regulator ( Set to ~ 40 - 41.7 PSI) >> Return to tank.

 

Thank you for taking the time to give me this explanation and diagram. This explains why I can’t find a part number for a fuel pressure sensor for this truck, and my scanner did not show a fuel pressure value.
I agree Old Guys Rule, but I am not so sure about Aged to Perfection.
Most times I think I am just aged!

 

Quick question about the fuel pressure regulator....well more a question of the vacuum line attached to it. When you remove the hose does it have vacuum? When I remove mine it doesn't and I can't find online if that is normal or not. The vacuum line from the regulator is attached to the air box pre throttle body so vacuum should be minimal right? Or do I have a vacuum leak somewhere? Fuel pressure at idle is around 44/45 psi (I bought a cheap Amazon gauge so i imagine its off a little and more like the stock 41psi). When I apply vacuum to the line the pressure drops so I believe the regulator is functioning correctly. Thoughts?

 

Make sure you insert the gauge with a tee and not deadhead the pressure into the gauge.


If you tee into the delivery tubing the regulator still works and reads the regulated pressure ~ 40 - 41.7 PSI.

If you dead head a gauge at the delivery tube it reads full pump pressure ~ 60 PSI.

While idling:

Standard: (40.8 to 41.7 psi)
• If the pressure is too high, replace the fuel pressure regulator.
• If the pressure is too low, check the connection between the fuel hose and fuel pump.

Stop the engine.
Check that the fuel pressure does not change for 5 minutes.
Standard: (21 psi)If the pressure is not as specified, check the fuel pump, pressure regulator and/or injector.

 

I used a t-joint like the fsm calls for so fuel pressure should be accurate enough. My question lies in the fuel pressure regulator vacuum line.

 

Fuel pressure regulator is referenced to atmosphere, no vacuum should be present at the port.

 

Cheap Gauge cheap results....

I would venture to say it is fine.