91-92 Vacuum logic diagram?

[mct75]

@LS1FJ40, do you still have the VSV for the FPR? Looking at my vacuum lines on the truck, there's an open one where I think this VSV connects. The PO disconnected half of the vacuum lines and looped hoses over the rest. I have a hard start, but once started it runs fine.

 

[LS1FJ40]

@LS1FJ40, do you still have the VSV for the FPR? Looking at my vacuum lines on the truck, there's an open one where I think this VSV connects. The PO disconnected half of the vacuum lines and looped hoses over the rest. I have a hard start, but once started it runs fine.

Not sure. I removed the VSV when I removed the EGR. I followed Spook'a guide to deleting it all. I'm not the most tech savvy person. My 3FE runs smoother now than it ever has.

 

[mct75]

So you removed the brown/red VSV? I think that's the FPR one.

I found some verbage on here and other sites about the purpose of the FPR VSV for similar Toyota EFI systems:

FUEL PRESSURE-UP SYSTEM

The fuel pressure-up system increases fuel pressure slightly on hot restarts for improved starting and idle stability. The pressure rise is accomplished by cutting off the vacuum signal to the fuel pressure regulator. The ECU controls the vacuum signal through the Vacuum Switching Valve (VSV). Pressure rise lasts for about 90-180 seconds after hot restart.

Fuel Pressure Control. The ECU sends signals to the fuel pressure regulator VSV to increase fuel pressure based on intake air temperature, coolant temperature and starting signal. By this system, engine restartability is maintained when the engine is hot. When restarting a hot engine, the ECU increases the fuel pressure above the normal level to reduce the fuel tendency to percolate. This helps restarting and also maintains the engine idle stability.

Operation. When the coolant temperature switch is ON (above 221*F) or higher, if the engine is cranked, the ECU turns on the VSV. As the VSV goes on, atmospheric air is introduced into the diagram [sic] chamber of the pressure regulator and the valve closes the passage. The fuel pressure becomes higher than the fuel pressure under normal driving condition by the amount of the intake manifold vacuum only. Even after the engine is started, the VSV remains on for several seconds.

This pressure-up system in conjunction with the blower fan that cools the intake manifold/fuel rail makes it sound like Toyota was chasing some vapor lock issues.

 

[lampleyc82]

Does anyone have a vacuum logic diagram from a 3FE FJ80? I have been searching for one that shows vacuum lines from a component and connection standpoint instead of a spacial "how it looks in the engine bay" layout.

This is the best spacial diagram I can find, but it's not easy for me to actually confirm what connects where. Like, how in the world is anyone supposed to trace all this out?

For example, here's a proper vacuum logic diagram for my 22R. You can actually see what connects where, instead of what it looks like and where it is. Does a diagram like this exist for the 3FE?

Does anyone have a vacuum logic diagram from a 3FE FJ80? I have been searching for one that shows vacuum lines from a component and connection standpoint instead of a spacial "how it looks in the engine bay" layout.

This is the best spacial diagram I can find, but it's not easy for me to actually confirm what connects where. Like, how in the world is anyone supposed to trace all this out?

For example, here's a proper vacuum logic diagram for my 22R. You can actually see what connects where, instead of what it looks like and where it is. Does a diagram like this exist for the 3FE?

Can anyone answer this question? I have no vacuum in any line. Truck runs, but not as good as it should. What would be causing that?

 

[mct75]

Can anyone answer this question? I have no vacuum in any line. Truck runs, but not as good as it should. What would be causing that?

All manifold vacuum originates from the black fitting screwed into the intake manifold that has two ports (on the runner for the #1 cylinder.) You should start there.

The EGR and EVAP regen vacuum originates from the ports on the throttle body. They will only have vacuum at partial throttle, not idle nor WOT.