LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

Ls400 starting issue when interior is warm

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Old 03-08-21, 08:45 AM
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Sin1UZFE
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Default Ls400 starting issue when interior is warm

When the car is cold, it will start right up first crank no problem. But if it has been driven for anything more than 5 minutes, it almost always takes two cranks to start up. And by that I mean the first time I start it itll fire then shut off after a second, then I can hold it there as long as I want continually cranking and it will never catch or even act like its starting. But as soon as I quit cranking it, wait a second, then start cranking again, it will start right up! If I press the gas pedal a little bit itll roar to life. After it starts its a champ.

I changed both coolant sensors, the fuel filter, checked fuel pressure, changed plugs (did had same condition before change, also since it needed it), checked spark also hear for fuel pump. But I did this when it was cool inside the car. Temps here have been around 34 to 50 recently went up to 80. Now its back down to 50. Thats when the interior is warm and when it happens.

I suspect fuel pump. Any thoughts?

Last edited by Sin1UZFE; 03-10-21 at 08:48 AM.
Old 03-08-21, 10:40 AM
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Superfast1
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Yeah, most likely your fuel pump is on its way out so you might want to get ready, especially if it's still OG.
Old 03-08-21, 10:45 AM
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Originally Posted by Superfast1
Yeah, most likely your fuel pump is on its way out so you might want to get ready, especially if it's still OG.
I ordered it lol...denso unit and gasket just in case.

I dont know if its the OG. But unlike most on it I dont know if or ever its been replaced. Might as well.

Last edited by Sin1UZFE; 03-08-21 at 10:57 AM.
Old 03-08-21, 11:40 AM
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Superfast1
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It's very easy to replace. Just remove the backseat then pop the round metal cover. Make sure the tank isn't full.
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Old 03-10-21, 08:48 AM
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Sin1UZFE
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Originally Posted by Superfast1
It's very easy to replace. Just remove the backseat then pop the round metal cover. Make sure the tank isn't full.
Hard to do with a pandemic but I gotta somehow drain 3/4 tank lol
Old 03-10-21, 12:20 PM
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avhart
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Beg to differ Superfast! I replaced my fuel pump already and although, like you said, it's relatively easy to get to, removing it is a rare pain in the ***. You got this 2" or 21/2" piece of rubber tubing right above it that attaches to the pump outlet line that I have found to be very difficult to impossible to remove in order to get the pump and bracket out. This is for my Lexus which is a 1992/93.

The solution which worked fine for me, was to completely sever the rubber tubing with a sharp utility knife or box cutter which then made extracting the whole assy, a breeze. Of course you need to make sure you have replacement tubing on hand before you start so you wouldn't have to go shopping for one. Also be careful when you are loosening the two tubing clamps so they wouldn't fall into the tank. Oh yeah, and finally you would probably have to cut the electrical connections to the pump (remember to disconnect the battery before you start!) in such a way that you would be able to re-join them later. Other than those things it really not all that hard.
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Old 03-24-21, 07:41 PM
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Fuel pump replaced. Resolved the issue. Got to 85 today so I parked in sun car was toasty inside. Has not done it again
Old 03-24-21, 09:00 PM
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Superfast1
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You should replace the fuel filter as well if you haven't done so. A clogged filter will make your new pump works harder. It's in the back near the rear axle.
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Old 03-24-21, 11:25 PM
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Originally Posted by Superfast1
You should replace the fuel filter as well if you haven't done so. A clogged filter will make your new pump works harder. It's in the back near the rear axle.
That was done a year ago

Last edited by Sin1UZFE; 03-24-21 at 11:59 PM.
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