Oliver Hermansen

A few days ago I was taking right in my 4x4 manual and she just shut off, not electronically. I tried to start it up but it would just crank with no sign of a pop. I got her towed home and started checking, I have fuel in the tank I have spark but the fuel pump does not prime or run when I crank it, but it runs when I jump it through the diagnostic panel, and i have fuel getting too the engine. I swapped out the EFI relay cause it was a ford one I got a new COR and I have checked over the fuses but nothing. I have also disconnected MAFS but still nothing. Any ideas before I really start tearing everything apart?

Thanks!
Oliver

scope103

Welcome to YotaTech.

Here's what I know about the fuel pump circuitry: https://www.yotatech.com/forums/f116...-quits-312747/ You will, of course, need a multimeter.

Just so you know, you don't have a "MAF" (Mass Air Flow sensor). You have a VAF (Volume Air Flow sensor). Different technology. Or just call it an AFM and you'll always be correct.

Oliver Hermansen

so I checked over everything mentioned there and every thing checks out except for the Fc terminal on the Cor. when I prop open the VAF the fuel pump runs but still no start and the is no power on the FC wire which I'm gassing is something along the lines of a fuel control signal coming out of the VAF? thanks for the help, ill be checking over that FC wire as the diagram tells me it ties the 2 together. should this wire be cutting off my fuel injectors?

Thanks again!
Oliver

2ToyGuy

Toyota has a nasty habit of doing things bass-ackwards. They switch the ground in and out of a circuit to control it, instead of the B+, like English speaking countries tend to.

With the truck's engine OFF and the VAFM vane closed, the circuit that holds the COR closed, to provide power to the fuel pump while the engine is running, is deactivated. The switch in the VAFM is open, thus, ground for the COR is missing. FC would therefore have B+ (+12VDC) on it with the key on. If you manually open the VAFM vane, it will ground the Fc wire, so the FC pin of the COR would read 0VDC, allowing the COR to activate, putting power to the fuel pump through the Fp wire.
SO, with the engine OFF, the key ON, and the VAFM vane closed, you should see B+ on the Fc pin of the COR. If the B+ isn't there,the COR is bad.
If the Fc pin on the COR still has B+ on it with VAFM vane manually pushed open, then the VAFM, or the wire between the COR and VAFM, or the VAFM E1 to ground wire, is bad.

This circuit has nothing to do with the injectors, other than putting fuel pressure to them. Bear in mind, the injectors get their B+ only when the engine is running, or at least turning over. They don't need to squirt fuel with the engine still, so no B+ to the injectors with the engine shut off. Even with the key to ON, nothing on the injectors. With the key to STArt, you should have a steady +12VDC on the injectors. Once the engine catches, the injectors get "fired", or get the +12VDC pulses, from the ECU.

You only need a few things for an internal combustion engine to run. Fuel, air, spark, compression, and the timing of all the things to happen at the right, well, time.. The trick is to figure out which one is missing, causing your engine to not run.

Is that babbling any help?
Pat☺

scope103

Not quite. The injectors have 12v to them as soon as the key is turned to ON. The injectors are opened when the ECU grounds the other lead. (I'll leave it to 2ToyGuy whether this common circuit arrangement is "bass ackwards.")

The description of the FC lead to the COR is correct; FC grounds one of the two coils in the COR to activate it. Just to be complete, the other coil in the COR is permanently grounded, and is activated with battery (B+) from the STArt circuit. All of this is in the FSM page I cited. Don't get fixated on whether one of these arrangements is "correct."

Oliver Hermansen

everything seems to check oue with COR and VAF, would a problem with the injector circuit cause the fuel pump to not run? and why wouldnt I be getting power to them? broken wire?

scope103

No.
Them? As in the injectors? How do you know you are not getting power to them?

Oliver Hermansen

I cranked the engine with the multi meter connected to the injector connector