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Discussion Starter #1
Before I do anything stupid: according to the diagram extract below, if I remove the fuel pump relay and apply +12V to terminal #4, the fuel pump will run at full speed and pressurize the fuel rail. Do you see it the same way?


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Discussion Starter #3
As for the viability of doing this without hurting anything, I wouldn't attempt it. What are you attempting to diagnose?
I've screwed up something while reassembling the fuel rail after cleaning the injectors, gas was squirting around when cranking and I couldn't see from where exactly because I was in the cabin. Either at the pressure regulator ("pulsation damper" in Toyota language) despite using new OEM crush washers (not tight enough?) or I dislodged something upstream the fuel line.
 

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If you can tell where the fuel is coming from, that would be best.

I replaced my injectors about 2 years ago and one of them was leaking pretty bad and had to basically do the install over again to make sure each of them sat properly.

But I see what you're trying to do, and i'm not sure which electrical lines you need to send power to, and if the signal is modulated or anything.
 

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Yeah +12v to pin 4 on the fuel pump relay looks to be correct to prime the fuel line.

BTW the fuel pressure regulator is in the fuel sending unit, in the fuel tank. The pulsation damper is something different. I bet you’ve lost a crush washer or they aren’t right enough. I did the same thing myself and got a gas fountain.
 

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Discussion Starter #6
got a gas fountain.
That's exactly what I got too. It was PITA to keep the crush washers aligned while keeping stiff fuel line with one hand and trying to find the hole with the pulsation damper thread in the other hand. I checked with a dentist mirror, both washers sit correctly. However, there's a chance as you say I didn't tighten strong enough because of the short universal wrench I used. Hopefully that's the culprit since anything else would be much worse.


BTW the fuel pressure regulator is in the fuel sending unit, in the fuel tank. The pulsation damper is something different.
Thanks for pointing out.
 

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Discussion Starter #7
And here's how I caused the gasoline fountain, @Kris OK was pretty right with his assumption. Failed to properly align the sturdy fuel line banjo fitting while screwing in the pulsation dampener. Will see soon if any damage was caused other that to the washer.

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Discussion Starter #8
+12V to pin 4 of the fuel pump relay worked perfectly for the fuel leak test.

Two tips for whoever reads this in the future:
  • Mind the plastic tab on the side of the fuel pump relay when pulling it out, it's not so obvious
  • Pulsation dampener has a wrench size of 22mm.

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