SpaceWizza

Hello guys,

I drive a ’05 ES330 and a few days ago my car decided not to start up. At first, thoughts were around the fuel pump, which kept silence when the key was turned to the ON position. The EFI and Ignition related fuses are OK. It looked like the pump was dead and I replaced it with a new one. After the successful replacement the car still won’t start up. Checked the fuses again – there are in good shape. So, I had to pull the pump out again to check if it works (know, should have done this beforehand) … and it works. The old pump is also working. Wow.

It turned out that the fuel pump is not getting any power from the fuse box in the engine compartment. After studying the fuse box diagrams, similar issues on the internet and doing ring out of wires with a multimeter, I came to the following:

• Anti-theft system – is not a case as I have a chip-key with a decent battery and, by the way, the security light turns off with my key in the lock.
• Wiring from the top cover of the fuel pump assembly directly to the fuel pump – wiring ok.
• Wiring from the designated “C/OPN - Circuit opening” relay (stupid naming, why not the fuel pump relay?) that provides power to the pump – wiring ok.
• Relay condition – checked with a 12V battery - It clicks.
• Swapping the relays with similar ones (HORNS, FAN) – nothing has changed.
• The voltage for the “C/OPN” is 9.0V (ignition ON), not enough to close the relay’s circuit.

Made a relay bypass there (jumper cable) to supply power to the fuel pump. The car starts like a champ so I was able to park the car in another place, as it got stuck in a multi-storey parking lot with no way for a tow truck to enter.

Guys, I kindly ask for your advice on why do I have 9V instead of 12V for the C/OPN relay activation. Hope for your help.

Pics:


LeX2K

9 volts where on the relay? Which pins? What is your battery voltage?

SpaceWizza

9V on the relay contact, which should close the circuit in order to supply 12V to the pump, but this doesn't happen since the are no other 3V.

The battery is good, easily cranks the starter.

LeX2K

Put a test light (has to be an incandescent bulb type) on the voltage supply side of the relay socket (I think you are calling that "relay contact") see if you have good power. A test meter alone is not useful here.

What is your battery voltage? I know the car cranks normally but still need to know for reference.

SpaceWizza

Got you, I will check it with a test light and have a look at the battery voltage with and w/o terminal connection.

What else would you advice to look at?

I have the Techstream on my laptop.

LeX2K

Not sure if you can monitor the signal going to the fuel pump relay with Techstream. See the attached PDF this is a typical fuel pump relay aka circuit opening relay on this era of Lexus. The suspected problem is on pin 1 of the relay not getting good power meaning it can't supply any current.

FYI to anyone that finds this thread via search, the fuel pump never gets power unless the engine is running or being cranked. It does not get power when the key is set to ON. Many people get snagged by this and end up replacing a perfectly good fuel pump.

Oro

Not on your list of wiring to check is any airbag wiring. Has any other work been done on the car? Any interior panels removed?

If any airbag or sensor is disconnected, power to the fuel pump circuit is interrupted.

SpaceWizza

​​​​​​Last weekend, I managed to get back to the car to continue my wiring journey.

I used a 12V test lamp on the relay's voltage supply side, it showed good power.
The battery voltage with and w/o terminal connection showed 12.33V.
​
A month ago I changed a timing belt with seals, pulleys, tensioner and serpentine belts. Replaced coolant and front engine support. Nothing has been done in the rear side recently.

​​​​​​Yes, bad airbags and loose connection in the SRS can be a problem that lead to cut of fuel, but Techstream showes no issues in SRS. However, checked airbags connectors in the back seat area. There are tighly connected.

I do not what happened, but know the fuel pump works and car drives normally.
Just out of interest, ckecked the voltage supply line of the C/OPN relay with a key in ON position (engine off) : 12V!

Strange things. Let's see how the car will drive these days, afterwards I'll write the outcome here.

Thank you guys for your responses!