1997 Ls400 cranks, runs and dies after 6 seconds
 

currently stumped with a 1997 Lexus ls400 with the 4.0 V8

car was towed in with a no start, found no fault codes stored or current.

fuel pump wasn't priming, so we replaced fuel pump, and fuel filter, car would then crank and after a few seconds the car would start but only run for roughly 6 seconds.

checked MAF , crank, cam, and FPR. found Crank sensor melted so that was replaced as well. and still getting the same results

going to check for bad grounds tomorrow,

Any thoughts?

Re: 1997 Ls400 cranks, runs and dies after 6 seconds
 

Check TPS and coolant temp sensor. Does it respond to throttle when it actually runs?

So the engine wouldn't crank at all until you replaced the fuel pump? I can't see there being a starter interlock that monitors the fuel pump, but never say never...

I'm guessing the melted crank sensor is probably unrelated to the fuel pump, unless someone jump started it wrong and killed a few things at once.

Re: 1997 Ls400 cranks, runs and dies after 6 seconds
 

That's what I would like to know. When it does run is it misfiring and does it have a response to throttle once it is started? Check and make sure all vacuum hoses are connected and connected in the right place.

Re: 1997 Ls400 cranks, runs and dies after 6 seconds
 

no response to throttle at all and when it is running, it does not misfire

Re: 1997 Ls400 cranks, runs and dies after 6 seconds
 

Have you double checked the fuel pump relay? Prior to the tow in, is there any known history or work done to the car? Was the general maintenance performed? I believe the Ls400 had a maintenance journal, if so take a peek in there and see what has been done.

Re: 1997 Ls400 cranks, runs and dies after 6 seconds
 

Like Fabrik8 said I'd also check the TPS.

Re: 1997 Ls400 cranks, runs and dies after 6 seconds
 

Fuel pressure regulator could be an issue. Check the relay like mentioned above as well

Re: 1997 Ls400 cranks, runs and dies after 6 seconds
 

The TPS could be bad, but it should still be responding to throttle if that is the issue. Adding extra airflow with no response obviously means that something is pretty far off, nothing new there. It's likely the timing is really far off. I'm assuming you've already checked the timing belt for proper timing, and the other suspects are the igniters/coils/whatever that engine has. Cam sensors are still on my list of suspects too, but it's strange that you're not getting any codes for that.

I would think that fuel system problems will give some change in RPM with extra air, even if it is running extremely rich.

What kind of ignition setup is on that car? It's not coil-on-plug from what I remember, isn't it some mirror image system where there's a completely separate ignition system for each cylinder bank?

How are you not getting any codes....?

Re: 1997 Ls400 cranks, runs and dies after 6 seconds
 

Agreed with above, I just didn't wanna jump to the timing issue again but let us know what you find out.

Re: 1997 Ls400 cranks, runs and dies after 6 seconds
 

ZERO CODES, not a single one, the fuel pump relay was tested, along with every sensor we could think of and find and the only one found to be bad was the Crank sensor, not to mention it was melted. and we don't do timing belts/ timing issues, my guys are good but not good enough, they do simple repairs, sadly i have to check out the majority of the cars because they stick to exhaust and brake work.