Hello everyone. I have a 1993 LS 400 with 333.000 + miles. Just had a new alternator installed, got home and car won't start. It sounds like it wants to start but won't.

Was reading some of the posts and read it could be the fuel pump or something under the hood that could be bad that causes the pump not to work.
My question is what is it that is under the hood that may cause the fuel pump not to work? I believe it was quoted that the part is $68.00. Where is this part that is under the hood?
Also does anyone know if you have to drop the fuel tank to replace the fuel pump? I believe it has never replaced.

Thanks for any help you can give.

 

Hello,

The fact that the car doesn't start doesn't mean that it can be caused solely by the bad pump. To diagnose the pump, take the Return Line off, then locate the Diagnostics connector under the hood, on the lid you will see the pinout of this connector, see if the Pin FP is still present, if so, then connect Pins FP and B+, which should force the pump to turn on even with no key in the ignition. Once the pump turns on the Return Line is off, you should see a steady and pretty good fuel flow, if not, then it is the pump. The pump is accessible from the interior, but the rear seat will have to come out completely to gain access, here is a complete guide.

Hope this helps and best of luck!

 

Thanks Arsennii for the information, One more question, I read there is a relay for the gas pump under the car can that also cause the starting problem?

There is also something under the hood that could cause the problem, where under the hood is that?

Thanks

 

Under the car..? I may be missing something, but to my knowledge there are no relays located under the car, no one would put them there unless they specifically want them to fail prematurely. Can you link an article that you were referring to?

To make a diagnostics procedure much easier, you need to see if the component works, not trying to find a component that hypothetically may fail. If it is an electrical problem, there can only be one issue - you don't have power to the pump, what causes it is a separate question.

To see whether it is an electrical issue, instead of chasing relays, send power straight to the pump as I described in above and see if the car will start, then you will know for a fact that you have some electrical gremlin, so that it will make sense to spend time going through relays.

If, on the other hand, the pump won't engage even after you supply power to it (which you will definitely hear if it works or not), then you will have to take the pump out and bench test it to make sure it is in fact toast.

If the pump engages even without you powering it, which you should tell by fuel pouring out of a return line, then the fuel supply to the rail is not what causes your car to not start, and you need to dig elsewhere, like spark or a vacuum leak.

Hope this helps and best of luck!

 

If I'm thinking of the right year car, the only fuel pump relay that comes to mind is under the hood on passenger side, bolted to the wheel well. (or in that general area) BUT that's only for the California spec cars. It's a black box that says "fuel pump relay" right on top.

Under the car near rear wheel on driver's side is the fuel filter.

 

i disagree. no spark will also cause a no start issue among other things.

i would check for loose connections during the alternator change. start with simple things first, even the battery terminals, before going to the fuel pump.

what part in the engine bay is $68? is that the fuel pump relay? that could just be shotgunning the issue w/o proper diagnostics.

if you're curious, you can access the fuel pump through the rear seat back cushion.
https://www.lextreme.com/lexus-ls400...ade-1990-1994/

 

Huh, seems like I managed to confuse myself there..

What I meant by it is the fact that a bad pump is by far not the only cause for a car to not start. The reason why fuel delivery is one of my suspects is because OP stated that the car didn't just cut off and is simply cranking into nowhere, it still has signs of life, and considering how simple it was to power the pump from under the hood in the olden days, I think it is an easy first target to check off the list and move on.

 

ah i see arsenii - i think after rereading your post i get what you were stating. i'm in error too for reading it too quickly perhaps!