hugo2648

2000 RX300. Car starts just fine. IACV cleaned.

However, for the first start in the morning, if I start it immediately on inserting the key, then the car will throw the P0300 code (multiple engine misfire). I am able to repeat this. THe car behaves normally once it gets going.

If instead of immediately turning the key, I turn on/off the ignition a few times, then no P0300 code. All is good.

SO I am thinking the fuel drains back to the tank overnight and I better install an inline fuel check valve (non - return valve). But where do I install it? How do I install it. I can find these 10mm hose barb type valves in all auto parts stores. Question is, all along the supply line, is there a flexible hose that can be disconnected and the check valve inserted? I would think installing it closer to the fuel tank would be the right place so there is a column of fuel in the line for first starts.

I would appreciate it if somebody can guide me or point me to a link on how to do this.

salimshah

Please don't reach out for bandaids before doing real diagnosis.

Pumps have a valve which prevent flow back and that is how they build up pressure, and it is in the tank.

I would suggest connecting a pressure gauge in the line and see if the pressure is built up
1. When you unlock and enter the RX
2. When you insert the key
3. When you turn the ignition on

Misfire and no fuel is a slight leap.

Salim

LeX2K

You can quickly find out if there is fuel pressure after your car sits crack open the fuel pressure damper (or the union in front of if accessible) if fuel sprays out no drain back. Wear eye protection!

It is very dangerous to rig up any type fuel tap unless you use flare fittings do it wrong and you can literally burn the car to the ground.

salimshah

Another possibility is injector leak which is letting out the pressure after a prolonged inactivation of the pump. <= just throwing ideas.

Salim