udelslayer

I'm trying to figure out if I should be able to hear the pump engage and/or there should be pressure on the Schrader valve where I'd hook up a pressure gauge to test.
The thing is that this motor doesn't run and I'm in the process of swapping it out but should I be able to cycle the key a couple times and build pressure that would cause fuel to release on the valve?

I didn't see any busted fuses or relay or whatnot and I haven't tested the end of the harness at the pump yet to see if its getting power at least. That's my next move.
I would have figured I could at least hear the pump run with the gas cap off, but I don't hear anything. Maybe I'm going deaf?

Thanks

______

udelslayer

Question....

So there is the EFI relay in the engine fuse box, but where is the C/OPN relay and how is it marked? There appear to be three at the kick panel to the left of the steering wheel, but I cant see any markings. I'm trying to figure out if its the harness, ECU or the pump itself. I'm hoping its the pump because thats an easy replacement.

FWIW, the schrader valve is not to the pressure side. I actually have no idea wtf that is there for an evap service. I think I'm going to have to do the quick and dangerous test of pulling the fuel line and having my assistant cycle the key to on and see if there is actual pressure in that spot on the line. I can't hear the pump, but the manual says I should hear it. I have read reports of xB owners that can't hear theirs either.

Does anyone know how the voltage would be read on the connector? If the key has been cycled on and the system thinks its primed, does it cycle on every time or not at all because its at pressure? The FSM seems to rely on their OBDII advanced diag tools a lot.

Thanks
J

udelslayer

and fwiw, I swapped efi and horn relays, with no change. I tested the relays, but they seem fine anyway. They dont seem like the normal box "click" type units that are under the dash, which is where I'm suspecting the c/opn is located to test.

samatman

I can't hear the fuel pump on the tC prime @ key "on" either. Swapping the relays was a smart way to rule out the relay as a cause. Are you sure the EFI relay is the same one as the fuel pump? I haven't had to do any fuel pressure testing on the tC yet but am in the process of doing it on another car that doesn't have a test schrader. So I'm adding a schrader onto a fuel filter banjo fitting adapter - cost $20. Something to consider if that would work on the tC's configuration.

udelslayer

According to others, and being a returnless fuel system that doesnt lose pressure on the rail unless something is leaking, it apparently doesnt prime. This is a safety feature that requires the CAS to convince the ECU to send a signal to the c/opn relay which is what controls the pump, but it must be also fed power from the efi relay - so a dual check system. If the engine stalls or some condition in an accident stops it, the c/opn opens and the fuel pump power is cut. You apparently cant and wont hear it without cranking the motor to send the CAS signal to the NE+, which makes TR1 send signal and power the pump.....I think, at least.

udelslayer

Weird, the posts showed up out of order....

anyway. Do you have a filter? I didnt notice one in the engine bay. I thought this thing only has the sock on the pump like a lot of cars these days.

I swapped the EFI/horn relay because there are 3 there that are the same and seem to be ok. It appears the c/opn relay is integrated into the j/b in the cabin to the left o the steering wheel. Replacement for that relay requires replacing the block/box itself. This is the only location you can jumper and force power to the pump to listen for it. You're not going to hear the fuel pump if you cant at least crank the motor because it needs the crank angle sensor input to complete the conditions that power the c/opn relay closed and then power the pump. It's some kind of secondary safety system I think thats part of their design in all toyotas. I have never done work on a toyota fuel system before, but it makes sense to me now. If something hit the engine bay that d/c the fuel hose (which I thought was quite unprotected) the engine would stall, but what guarantees the pump shuts off if the key is in the ON position? Subaru tries to protect this by their GBOD (green brackets of death we call them). In toyota, its this c/opn relay thats dictated by knowing the engine is turning. I have never had a fuel system problem in the 10 or so toyotas that my family has owned, so I had never considered an issue until I realized that I dont hear a fuel pump....but thats because you're not supposed to hear it. I know, it sounds kinda dumb lol. I always heard it prime in my wrx. I always thought that giving that extra second for prime when starting your car was a good thing to do for longevity, but it seems it doesnt even matter.

I like to understand what does when where and how. Now I want to know how Honda does theirs.

samatman

I haven't done any work on toyota fuel systems either so I made some assumptions based on other cars which were obviously not correct. I looked at the service manual spaz posted and the filter is apparently in the pump assembly along with the regulator. I also thought there was an inertia cut off switch, and there doesn't seem to be one either. So while useless, you can think of my posts here as a friendly thread bump

udelslayer

No, there isnt an intertial cut off for these either like there are on some fords. In fact, the design is pretty simple when you get past all the electronic self-checking it can do. If the regulator is in the tank, whats the white thing on the fuel rail (drivers side). I thought that might be some kind of regulator but I saw an explanation stating thats only to "smooth" the pulse generation from injector firings.

Thanks for the bumpage.

J