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Discussion Starter · #1 ·
Hi, I have a 1992 MR2 Gen II with EMU black pnp. The car have a basemap loaded on it started for 3 seconds and died, I have a FPR gauge seeing the fuel pressure just dropped down to zero when the car started. Wonder if anyone have a similar issue on their car. I tested out the output I do not hear the fuel pump kicks on at all.
 

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Discussion Starter · #3 ·
I have not done that yet. That’s what I’m planning on doing tomorrow, it’ll be jumping the diagnostic port in the engine bay +B and FP pin?
 

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The Circuit Opening Relay (C/OPN in the fuse box) controls power to the Fuel Pump Resistor Relay (in the engine bay).
On the standard ECU when you turn the key to START it powers up the C/OPN Relay which powers the fuel pump. The ECU will switch the FPR Relay to 12V bypassing the Fuel Pump Resistor using the FPR pin on the ECU for starting and when on boost. When the ECU sees the engine is running it will switch 12V from the FC pin to the C/OPN Relay keeping this relay closed. Once the engine is started the Fuel Pump Resistor relay switches back to the default setting to run through the Fuel Pump Resistor when at idle and low load.

So something in this circuit is missing it's control function. Based on the short running time it could be the FC pin.
A few tests can be run here.
1. Jump FP and +B in the diagnostics port. You have done this so we know it's the fuel pump control system.
2. Remove the Fuel Pump Resistor Relay and jump the 2 Blue w/Black wires with another thick gauge wire to see if it is the relay or the control from the ECU to this relay. This will run 12V from the C/PON Relay to the pump.
3. Remove the Resistor and jump the pins. This will show that the resistor is at fault if the car runs fine. Doing this make it run 12V to the pump as per point 2.

As a note, the MR2 does not prime the pump system when the key is switched to ON.
 

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Discussion Starter · #10 ·
Another problem is that the ecu is staying on even when the key is off. I’m not sure what is causing that but when I put a jumper between FP and +B the ecu will turn off as it should when key off. Wonder if anyone have any insight?
 

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That's really odd.

We know that an ECU normally has a constant power for memory and a switched power. What are your power sources? How are they controlled?

Jumping the FP and +B should have no affect on the ECU power unless it's not wired properly, then I have no idea what has been done.
 

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Discussion Starter · #12 ·
It should work like OEM because it’s running off the oem harness. It’s very strange jumper the FP and +B it leads me to think it has a power tapped off somewhere
 

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Sorry, should have clarified.

I guess first off, does the fuel pump run with FP and +B jumped when the key is switched to ON?
Then, if that is the case, does the engine still run after 3 seconds if this is still jumped?
 

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Discussion Starter · #16 ·
Sorry, should have clarified.

I guess first off, does the fuel pump run with FP and +B jumped when the key is switched to ON?
Then, if that is the case, does the engine still run after 3 seconds if this is still jumped?
Yes the fuel pump run with FP and +B jumped and car still run after 3 seconds. Without that jumped the car does not stay on after 3 seconds. That’s what I’m confused about, the PO removes the fuel pump relay and Jumped those two wire but I just added it back on. I can hear the relay buzzing when the car crank or invert the fuel pump output. I’m thinking either the relay is bad or bad ground
 
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