BigErn

Hi All,

I am new to this forum and have been having issues with my 97 LS400 with 177k miles. About 6 months ago I started having this issue where I will start the car cold and it starts and runs just fine. I will drive around running errands and park my car at the store. I come back to a warm car and sometimes it will crank and turn on for a few seconds and then flutter and die. Try to start it again and it won't start. Let it sit for 4 hours or overnight and when I come back it starts like nothing happened. Its been progressively becoming more frequent. It sounds like it's not getting fuel when it does occur. Most recently it won't start again the next day and when I get in the car I am hearing strange electronic type noises from the rear drivers side door or under the rear drivers side seat (near the fuel pump etc..) I've been following numerous threads and think I have it narrowed down to a few things. When it is running it will sometimes run rich and it gets bad MPG Thinking its bad capacitors on the ECU, bad fuel pump relay, bad fuel pump? Hesitant to say its the fuel pump bc they are supposed to be very reliable on the LS. I have an audio clip which I can't attach bc of the size of the file of the noise Im hearing when I turn the ignition to the on position prior to cranking (first noise). The other noises in the clip come after I have tried cranking with no luck...Any thoughts, direction, help would be greatly appreciated. Sounds like an electronic noise that is not allowing the fuel pump to turn on and it just cranks.

Oseberg

Try checking your engine coolant temperature sensor. When the engine is cold, it needs more fuel to start and run, (like the choke on an old carbureted engine).

If your temperature sensor has failed such the the computer always believes the engine is cold, it will be like trying to start a warm engine with the choke on. The engine will probably become flooded and the become impossible to start.

The temperature sensor just looks like a resistor that changes with temperature. You should be able to disconnect it to make it read either cold or hot, then short it with an appropriate resistor to reverse it. You can also test the sensor with an ohm meter.

Also, when the engine is warm and failing to start, if the temperature sensor is the problem and the engine is flooded, of you press the gas pedal all the way down, it will put the engine in, "clear flood" mode and the injectors will not inject any fuel at all. You can then crank the engine. If it is flooded, it will blow air through the engine with no fuel until the air fuel mixture is correct, fire for a second, then stop because there is no fuel. If it fires for a second with the gas pedal all the way down, then you have just verified that it was indeed flooded and now it is not flooded. You can then try to start it normally again and it might start, but it might just get flooded again.

In any case, these experiments will give you more clues as to what the problem might be. It could be a corroded temperature sensor connector, or a broken wire.

Let us know how it goes.