MacPro 3.1 does not start up

The "approved method" for debugging these difficult situations is to strip your Mac Pro down to almost nothing. Remove everything that is in a slot, including all PCIe cards, ALL drives, all RAM, looking for the machine to stay on long enough power the fans and blink a "Help me" message in the power-on light.

If you get to that, install the RAM and you should get a chime.

If successful there, try the graphics card and see what is on screen.

then keep adding one thing at a time and see where it gets stuck.

page 152 seems to be saying your power supply is not working:

Power Supply Verification

To power on, the computer’s logic board requires “trickle” power. If the system fails to power on, first reset the SMC as described in this chapter. If the computer still doesn’t power on, follow the procedure outlined below to determine whether the issue is related to the power supply.

Verify trickle power

Diagnostic LED 1 indicates the presence of trickle power required by the logic board to begin the startup process.

LED 1 should be yellow when the DIAG_ LED button is pressed, indicating that trickle voltage is present.

Verify Power Supply Is Providing Power

Diagnostic LED 7 indicates that the main power is OK and within regulation. Plug in AC power cord, and press the power-on button on the front panel.

LED 7 should be green when the DIAG_ LED button is pressed, indicating that the main power is OK and within regulation.

If diagnostic LED 4 and LED 5 are both solidly illuminated at power up, improperly seated power supply cables could be one cause of this behavior. Check all power supply cable connections to ensure they are properly seated.

The only slightly different thing I would try is holding the diag button while pressing the power-on button to see if LED 7 Power-ON lights up at all.

<< You mention the front panel board; is it the small piece with the power-on button? >>

Yes, exactly.

if your power supply is OK, then the same symptoms (nothing happens when you push the power-on button) could be caused by a bad power-on button on that little board.

There may also be a pair of pads on the mainboard you could short across to do the same as the Power-on button. But I don't recall exactly where they are located. Likely near the front panel board's connecting cable.

The way I read that business about the indicator for sleep is that the Position is on the board, but it has no LED installed in production units, because they decided to use the power-on indicator instead.

There may be some tiny labels next to the LEDs on the board.

The trickle power is an "always-ON" (when the plug is in the wall) supply needed to have some power to run the logic to start up everything else. If you have no trickle power, you can't use the button to start up, even if the rest of the power supply works great.

If you are not getting the Power-OK indication, according to the manual, then your power supply is not coming up and settling at OK levels.

If you think the supply is OK, that could implicate the Front panel board.

You said you had another working Mac Pro 3,1.

I recommends you borrow its board and test before you pay money for an extra part.

Press the power-on light, and stand back.

The fans should come on.

the system may sit for a moment.

then the power-on indicator will blink a small number of times, then go dark for a few seconds.

then the power-on indicator will blink a small number of times, then go dark for a few seconds

again.

again.

forever

the number of times encodes the message it is trying to get out to you.

To get the lamp to blink, the System management controller must power up and run the fans. (Fail-safe is maximum speed.)

If you dropped the power in the process of removing boards, you already did an SMC reset.

The main processor must be able to start the self-test, but no RAM is required to be present or working.

So if you can't get it to blink the power-on light, it is stuck pretty far back in the process, and the pile of boards and drives you pulled out are not involved in any way.

if it lights up Standby power, that means the small "always on" power supply required to start up is present.

start on page 154 with the main "startup failures" section and work through the flowchart.

It looks to me like If you think your power supply and front panel board are good, the next step appears to be to replace the mainboard.

As I said, your computer does not beep, it blinks.

Information form that article suggests you may have lost integrity of your RAM. Try swapping some RAM Risers and DIMMs around in a methodical way and see if you can get it working again.

There is not very much "stuff" on the main logic board. The items most likely to fail are the things that have the most transistors, and the things that get the hottest.

Memory would be high on the list, but you don't need ANY memory to do these tests.

Power supplies and processors get hot and have high parts counts.

Referring to page 148, what is the state of the diagnostic LEDs?

any change when you press the power-on button ?

(the door in not interlocked, and the only danger is if you put your fingers in a cooling fan)

the pages that follow have suggestions about what to expect.

without the graphics card installed, you can not get "EFI-good", but you are not getting that far anyway.

The power-on indicator will blink. One, two, three times or so. Then it will pause, then repeat. The fans should stay on.

It can't get enough working to do anything more, just blink the light under ROM software control.