Diamonback

I recently bought a 95 SC300. The car has only 90,000 miles. It was parked for at least 3 years. I drained all the fuel from the tank but but after putting new fuel in the gas tank, the pump gave out. I replaced it with a cheap one from eBay. I know better but I didn't want to spend a fortune on a fuel pump before I determined what else was or could be wrong with the car. Before installing the new pump I clean the injectors, fuel rail, fuel line from the tank to the filter and filter to the rail. New spark plugs new valve cover gaskets, clean the throttle body as well. The car ran great for several days, although that cheap fuel pump was pretty loud. The issue I'm having is that I have no fuel pressure, and I read 12 volts or so when I first turn the key to the on position, but then the voltage steadily Falls until it gets to zero. I can run a hot wire to the pump, and it works great. The fuel pump relay in the main distribution box is functioning. Having a separate fuel ECU is something new to me. Anybody have a suggestion or a direction to point me in. I've worked on lots of cars for a lot of years but this SC has some peculiarities that I'm not familiar with. I figure I could hot-wire the pump and the car will run fine but will most likely cook the pump in no time. Rather than do that, I'd like to fix it the right way. I would certainly appreciate suggestions as I have read many posts on this forum and it seems as though some of you cats know what you're talking about. Thanks in advance.

Love my new(classic) Lexus, just need to work out the bugs and blow out the cobwebs.

Diamonback

BlackIRON

Umm I believe there are various threads around here speaking of a Fuel pump ECU mod like > https://www.clublexus.com/forums/per...tures-faq.html

But i myself did this mode as the ECU sits just behind the driver seat in the panel underneath the Seatbelt (Housing?) and just ran the hot wire to always be on. i heard the pump but thought nothing of it as even driving noise drowns it out. I did it on a 96 sc300 and it lasted for atleast 15k miles that i drove it and even after i sold it its still "strong" i never took an actual look at the pump but it solved a fuel starvation issue that was hard to diagnose coupled with a Tb issue. These cars are alot of fun and even more fun to drive when you treat them right.

RXRodger

iTrader: (2)

There is no issue with putting 12 volts to the fuel pump, that is the voltage it gets from the fuel pump ecu when above an idle/no load. The problem with hot wiring the pump by bypassing the fuel pump ecu is only a safety concern. In the event of a wreck or fire, the fuel pump would continue to feed fuel instead of the main ecu telling it to stop. So, the best way to do this with a working fuel pump ecu is to wire in a relay. As BlackIron has said, there are numerous threads on here on how to deal with the fuel pump ecu including how to wire up a relay. I have done it on 2 cars and need to do the same on my white car before the fuel pump ecu dies on it. You can find used ones for $30 or $40, so find a used one in working order, buy a relay, wire it up, never look back.

mtd2198

when you removed the gas the fuel pump dried up,
reson to always keep 1/4 tank of gas in it.
could be the fuel pump ECM.
check your fuses.
I had a fuel ECM go bad, fuel pump works only when hot-wired just like yours.
look at the wire schematics and see if there are other switches/sensors.
fuse or ECM. is my guess.