odomfl

There is a chattering noise coming from the relay/fuse area (inside)of my RX-300. I believe it is coming from the fuel pump relay, at least I think it's the fuel pump relay. The chattering noise only happens when the engine is running. There also appears to be a chattering from the fuel pump area underneath the fuel tank. Has anyone had a similar experience? Will this chattering damage the fuel pump if I try to drive to the repair shop?
Thanks,

Lexmex

Well, I can usually hear chattering inside my RX and I know it could be either my injectors or my air intake (the latter not applying to most).

As far as the fuel pump, I can usually here a sssss sound below the vehicle, though not a chatter as you put it.

I wouldn't see any issue in driving it over to the shop unless you are noticing something other than the sound such as a difference in drivability.

salimshah

This is a generic theory about fuel pumps ... which may or may not aplly to RX (have not had a need to study it). I am just sharing it, so that readers appreciate how smart the vehicles are.

Electrical pump is located in the fuel tank. Having (rougly) more than 1/2 a tank full keep it cool (extends life). There is a built in pressure switch that cuts out the pump after cetrain pressure is reached beyond the valve. To test the pump, all the mechanic has to do is connect a pressure gauge to the fuel supply line and read pressure should match the cut off.

The pump is energized once the key is inserted (or turned on). This is referred as priming up the gas line.

Now think safety ... accident with a break/cut in the supply line say in the engine compartment. [Dont confuse this with a leak in the tank]. The pump will keep sending pressurized fuel till the driver switches the key off or pulls it out.

This is where the relay comes in. So the relay stays engaged as long as the engine is running. (typically rpm sensor/ditributor).

There is an eletrical bye pass for pre-start time (when the engine is not running) which can be built with stuff around the relay or logic based on key position) .. which can be part of the ecu in RX.

With this understanding the orignal post does not lead us to a systamatic way of narrowing down the problem.

Salim

btheurer

i have a 2000 rx 300 as well and just replace the fuel pump and it ran great, next day doesn't start again. is there a fuel or relay to check?

salimshah

Please understand 'does not start' is very vague.

Does the starter spin?

Remove the key from ignition (physically take it out). The fuel line enters the engine way below the brake vacuum booster. There is protective plastic "U" cover that you can squeeze and take off. The fuel line has a quick connect (1/4 turn) and it leads all the way up to the throttle body. Be careful as the fuel is under pressure and you should see it squirt out as you disconnect. Key inserted in ignition turns the fuel pump on.

Salim

manianac

I'm currently on a road trip and am experiencing the same relay chatter. Whenever the throttle is closed, I can hear the C/OPN relay chattering away in front of my left knee. Swapped it out, still chatters. I'll have to diagnose it when I get home, but haven't found anyone else but this thread experience anything similar.

carguy07

Make sure your battery/charging system is healthy. These cars will make all kinds of noise from the relays when the battery is dying. Any chance your clock has reset itself to 1:00?

manianac

Clock and radio presets are still good. Checked with a DVOM real quick, battery+charging system is working fine. I should also note that the chatter happens even when the engine is at 3000 rpm on the highway and I let off the throttle. Goes away when you re-apply. Going to get a Techstream on it later this week.