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Where do I find the Circuit Opening (C Open) Relay for the fuel pump in a 2004 RX330?
What colour and shape is it?
A picture or workshop diagram would be very useful.
Thanks!
Thanks. Looks the same as the EFI, Horn and A/F relays in the relay box in the engine compartment behind the fuse box.
But can't see a "C Open" relay anywhere....
Wondering if it is hiding under the dash somewhere?
Where do I find the Circuit Opening (C Open) Relay for the fuel pump in a 2004 RX330?
What colour and shape is it?
A picture or workshop diagram would be very useful.
Thanks!
Hi Gecko2.
Your first post and thread so Welcome to Club Lexus!
Please tell us the story on your car and what's going on in as much detail as you like.
From my experience people like to help more if there is more info.
2004 RX330
What should the voltage be at the fuel pump when cranking?
I measured 9V, but thought it should be 12V when starting?
For a RX350:
"The fuel pump relay is turned ON while the engine is idling or operating at low load. This causes current to flow through the fuel pump resistor to the fuel pump. The fuel pump then operates at low speed. The fuel pump relay is turned OFF while the engine is cranking or operating at high load. The fuel pump then operates at normal speed." https://www.clublexus.com/forums/rx-...l#post10182372
My daughters 2004 RX330 has a "cranks, but no start" problem.
Spark plugs have spark but no fuel.
No fuel to fuel rail so I replaced the fuel pump and filter.
Now get fuel at the fuel rail but not to the spark plugs. Injectors appear to be opening (have 12V at all injectors) based of feeling them. Not 100% sure though.
No error codes. All fuses and relays good that I can find, but can't find the C Open relay for a RH drive car.
Voltage at fuel pump is 9V, thought it should be 12V (see new thread).
I am guessing low fuel pressure?
Next step I guess is to test fuel pressure, I assume this must be done at the fuel pump assy with a T-line?
Doesn't appear to be a place to put a T-line in near the fuel rail, as there is no fuel return rubber line.
Also could supply 12V to pump and see if this helps to start, or increases fuel pressure?
My daughters 2004 RX330 has a "cranks, but no start" problem. Spark plugs have spark but no fuel. No fuel to fuel rail so I replaced the fuel pump and filter. Now get fuel at the fuel rail but not to the spark plugs. Injectors appear to be opening (have 12V at all injectors) based of feeling them. Not 100% sure though. No error codes. All fuses and relays good that I can find, but can't find the C Open relay for a RH drive car. Voltage at fuel pump is 9V, thought it should be 12V (see new thread). I am guessing low fuel pressure?
What fuel pressure should I see when cranking?
I think fuel pressure should be around 45psi with engine running?
Next step I guess is to test fuel pressure, I assume this must be done at the fuel pump assy with a T-line? Doesn't appear to be a place to put a T-line in near the fuel rail, as there is no fuel return rubber line. Also could supply 12V to pump and see if this helps to start, or increases fuel pressure?
My daughters 2004 RX330 has a "cranks, but no start" problem.
Spark plugs have spark but no fuel.
No fuel to fuel rail so I replaced the fuel pump and filter.
Now get fuel at the fuel rail but not to the spark plugs. Injectors appear to be opening (have 12V at all injectors) based of feeling them. Not 100% sure though.
No error codes. All fuses and relays good that I can find, but can't find the C Open relay for a RH drive car.
Voltage at fuel pump is 9V, thought it should be 12V (see new thread).
I am guessing low fuel pressure?
Next step I guess is to test fuel pressure, I assume this must be done at the fuel pump assy with a T-line?
Doesn't appear to be a place to put a T-line in near the fuel rail, as there is no fuel return rubber line. Also could supply 12V to pump and see if this helps to start, or increases fuel pressure?
Thank you for the extra info.
It helps to see what you have going on and it seems like you have some experience and have done some testing.
Ok, If I may suggest- Do not power the fuel pump directly by voltage injection unless you know what you are doing.
Risk of bodily injury/death to self and property damage.
Reason: the power plug to the fuel pump is located under the carpet under the back seat in the direct location of the gas tank, if any fuel vapors are present due to failing emissions parts or fuel pump gasket- make sparks injecting voltage- kaboom!
Now with that out of the way, being careful finding somewhere else to inject the +12V to power fuel pump is what a tech would probably do just for a quick test for fuel delivery.
*Note- if I remember- while cranking you should have +12V but after the engine is started, the power to fuel pump is routed thru a "fuel pump resistor and will be lower.
*Note- if you see a voltage drop before the fuel pump as measured to frame ground you have a power delivery problem possibly from the Copen relay- I will confirm location for you on next post when I have time to dig up the info. ALSO, you could just as well have a bad fuel pump ground raising the fuel pump's negative to above frame ground potential- you will need to confirm a good frame ground at the fuel pump plug.
Put your volt meter on the battery and note the voltage while cranking you'll find it is about the same as what you found at the fuel pump.
Good one Lex2k, maybe when cranking there may be less that 12V at the pump if any system wide voltage drop, didn't think of that.
Hopefully there is a thread somewhere where someone has measured it while cranking.
Good one Lex2k, maybe when cranking there may be less that 12V at the pump if any system wide voltage drop, didn't think of that.
Hopefully there is a thread somewhere where someone has measured it while cranking.
Unless you have something like the Antigravity battery it is not 12 volts! In super cold weather I've measured 6.
Here's a diagram, should be under R/B 2 cover where ever that is
Very, very, very close, right next to and touching it is is a very small box RB 1, if it's where I think it is, hoping.
// Below is for OP
It's a small auxilary box and it's under the brake fluid reservoir so you'd never find it if you didn't know it was there but it touches RB 2.
Remove one bolt and slide the reservoir out of the way for access to the RNB 1 box cover.
Also, I've been in that box and can't remember 100% but I think that's where the relay is- if not let me know cuz that means it's behind the speedometer and that's why the drawing below is so deceptive. Ya'll will see what I mean when you check it out below.
CORRECTION- I cannot find any reference to a "fuel pump resistor" on the RX330 so I believe this is exclusive for RX350 only. The info quoted above from another thread does not appear to apply to the RX330. If I am in error plz let me know so I can update this and keep looking for it in the system schematics, but haven't found it yet so assuming no "fuel pump resistor" for now.
*Note- for RH drive it will probably be "Cowl Side RH" on your car.
(Posted in fair use for discussion)
>> Find R/B No.1 below, yours might be on other side of the car for RH drive.
FUEL PUMP CIRCUIT- RX330
>> Fuel pressure Test- PM me if you need full procedure. Seen below, using a Tee to tap into the fuel line at the connectors- location is under the hood.
>> Please post your results and your fix if you are successful in case another member needs your info in the future. Pics are a plus too.
Made a little progress.
Battery voltage cranking 10.8V.
Fuel Pump voltage during cranking 10.5V, same for chassis earth and fuel pump wire earth.
Less than 1ohm resistance between chassis earth and fuel pump wire earth. So voltage good to fuel pump.
Could have a failing c/o relay which passes voltage but not much current?
Used stethoscope and could hear injectors clicking, so they are working.
Still have fuel at the fuel rail, checked by cracking the banjo bolt on the fuel rail end.
Still can't find the circuit opening relay box. Will keep searching.
At the moment I don't have a suitable fuel pressure test kit so haven't been able to check fuel pressure.
Need to find one.
My guess is still low fuel pressure. Maybe failed pressure regulator?
Is there a section in the workshop manual to test the fuel pressure regulator?
Could have damaged an o-ring during fuel pump install or bad wiring somewhere....
Made a little progress.
Battery voltage cranking 10.8V.
That's good.
Could have a failing c/o relay which passes voltage but not much current?
If the fuel pump is an open circuit, yes it will show voltage but when loaded will go to zero. Put a test light right at the pump it has to be one with significant load, incandescent bulb.
My guess is the COR is tucked up under the dash drivers side. That's about the last component in the chain to fail. Can you verify crank sensor pulse? No crank pulse=no start.
12-29-22 | 08:28 PM
Circuit Opening Relay Location
