Fuel Pump

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Lextreme II

Lextreme II

Active Member
My car is almost ready to go, but no fuel pressure. The fuel pump is not getting power. I tested the fuel pump relay and no juice. What could be the problem. ECU? or other possibilities? Help asap...
 
Lextreme:

I don't know the engine management systems on the Lexus, but it might be a couple of things:

- broken wire, bad connections.
- no ignition pulse to, trigger signal out to fuel pump ( might not be on Lexus )
- anti theft. if you have an alarm it might have disconnected the fuel pump.
 
Fuel Pump should turn on when you put the key in START.
I'm not sure if it should prime for a few secs before though.

So the fuel pump relay has +12V ignition on one pin, earth on another pin, +12v on start/run for another pin, and last pin to fuel pump.
 
No juice and no priming either. Need help fast...... fully built motor with GT40 sits idling for some fuel.....
 
What happen if i bridge FP and B1 together? Would it bypass the relay or ecu? The Dx box inside of the car or in the engine bay?
 
the ls400 are **** fuel system

they have relay for this and that just too complicated
first u need to check signal from ecu to trigger circuit opening rel;ay
then they also have a fuel p[ump relay from what i remember the fuse box setup

then the signal goes to the fuel pump

nothin is straight forward these days the dumb car manufactures make it too complicated
 
the "FC" pin on the ecu switches to earth to activate the Circuit openning relay (CoR)
The FRP pin on the ecu switches to activate the fuel pump relay, and takes input power from the COR.

hence no COR, no fuel pump.
 
Lextreme said:
What happen if i bridge FP and B1 together? Would it bypass the relay or ecu? The Dx box inside of the car or in the engine bay?
Click to expand...
It gives the Fuel Pump power when ever the key is on.

If the fuel pump isn't on with the bridge in, then the COR is stuffed, or EFI Main Relay is stuffed, or you have fuses blown.

Dx box in bay.
 
A quick and dirty solution to get it to run is simply run a lead from the battery dierct to the appropriate fuel pump terminal on the fuel tank.

I guess an LS is like an SC where it has 5 or 6 wires leading into the fuel pump/gauge sender in the tank.

At least if you get it running you can confirm for us all it works.
 
Sounds like its time to get out a multimeter and test for voltage at various locations.

Also check earths. My cressida died a few years back and it was the earth on the fuel pump that got dislodged.
 
I had the same problem with a fuel pump in the Cobra's tank, the power lead had come adrift.......I was so convinced I'd killed another fuel pump that I went and broke a cardinal rule and bought a brand new one from a proper parts emporium.

Opened up the tank and the power lead was swinging unattached to its connector.

Cheers,

Tony
 
Would installing wrong cam setting affect the fuel pump or electrical system? I know the ecu gets its signal from cam and crank sensors. Could this be the problem? I remember my engine builder installed the cams, but the mechanic uninstalled and change the setting (teeth) and he stated that the engine builder did it wrong.

Puzzle.... Puzzle... right now the cams are coming out and reset it again.
 
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