94 ls400 157k non air ride
alright i have been having this issue back and forth with my ls400 for the past couple months. the car will run and drive fine and then ether it will not start after being driven or will began to start cutting out as i am driving the car. i had this issue a few weeks ago had the car towed home and have been trying to figure out this issue since. I talked to my local Lexus dealer and they said for me to check the fuel pump relay they gave me the location of the relay and where they said it would be is not for the fuel pump, it is labeled air pump. I will take pictures if that will help with that. If someone could direct me to where it is or give me a picture where this relay is located that would be wonderful thank you in advance.

 

first step to any 1LS electrical issues: rule out the trunk hinge.
www.lexls.com/tutorials/lighting/bulbout.html

 

Honestly?
Your reply almost looks flippant.
The link suggests problems with light related systems, which would make sense back in the trunk hinge area.
Perhaps you could state for the record that the fuel pump wiring shares that harness (?) and is susceptible to intermittent failure?
Colin

 

Fuel pump relay on my '92 is under the big electrical cover in the engine compartment. It resides next to the A/C clutch relay and should be clearly marked in the diagram inside the cover.
I have switched those two relays with each other to get home after an intermittent stalling problem in the heat of summer. Fuel pump was happy to use A/C relay.
Colin

 

The symptoms the OP described don't indicate a fuel pump failure, but do indicate an electrical gremlin/sensor issue of some type. trunk hinge harness issues have been exceedingly well documented for everything from cluster issues, rough motor, gear selector issues, reverse safety switch issues, and more. Combined with the near certainty of the problem occurring on the 1LS, it becomes the first stop for any suspected electrical issues.

feel free to search for previous threads detailing such findings.

 

where they told me the fuel pump relay would be is where its the air pump in the fuse box it looks just like this
http://media.photobucket.com/image/r...s/DSC08684.jpg < not my car but same relay in that location.

 

I completely agree with PureDrifter. Having had the left trunk hinge wires break on the 90 LS I owned for (too) many years, I can testify that the OP's issues are consistent with that problem.

 

I will make a note of that ... fricken cars. BMW had exactly the same issue with wiring harness damage at the hinge.

Fuel pump relay over on the left side of the car under the fuse box cover near the coolant reservoir.

 

Just had same/similar issues. If you haven't figured this out yet try the following:

Start your car and go to the EFI relay. Wiggle the relay and see if the engine either stalls or your idle fluxuates. If so get some dialetric grease and pack as much of it as you can down in the slot the EFI relay goes into. It worked for me. Good luck.

 

if it is not the trunk hinge, next most likely candidate is the ECU capacitors

go ahead and be skeptical, but when you get tired of fighting intermittent electrical/cutting out/no start issues, fix the capacitors as per the thread and you will be back on here offering to buy me Christmas presents!

 

Doesnt the 93 and 94 have a fuel control computer?

 

Ok... I have a 94 LS400 and I liked to killed myself finding Fuel Pump Relay/ECU/ECM. I called Lexus and they told me it was under the hood under the front passanger side. Nope. Next it was under the back seat. Nope. What should have taken 20 minutes to change, turned out to take hours to find. Hopefully this will save somebody a ton of headaches.

The fuel pump relay/ecu/ecm is located in the trunk by the gas cap. You have a little tool kit in the trunk and when you remove the plastic door there are 2 screws holding it in place. Behind this is Fuel Pump Relay/ECU/ECMy.

I found a used one on EBAY for around $50 bucks. You can do a search on
93 94 LEXUS LS400 FUEL GAS PUMP CONTROL MODULE COMPUTER ECU ECM RELAY