Lexus082

Short Version:

SC400 random stalling: found fuel pump ecu to be bad, bypassed the ecu, car was fine for 2 weeks, then it stalled out twice and was difficult to start. Fuel pump was running in high speed for those two weeks and since the engine stalled out a couple times now there is a bad misfire causing the engine to shake. My best guess is the fuel pump went bad and is weak causing the misfire(s).


Long Version:

Recently I found my fuel pump ecu was bad which caused the engine to stall. I used a paper clip and jumped the two pins (Fp & B+) and the car continued to idle without stalling until I disconnected the paper clip and then it immediately stalled out. As far as I know this is how you test your fuel pump ecu. So I decided to bypass the fuel pump ecu, which would cause the fuel pump to constantly run at high speed.

I drove the car for two weeks without any problems until I was at a red light and the engine stalled. It took a few attempts to get the engine started. The car was ok until the following day. I noticed it was hesitating while I drove to the store. I parked the car and came back out and when I went to start it, it just turned over but wouldn't start until a few minutes had gone by and I had to give it some gas to get it started. I drove about a mile and it stalled out on me. It took a couple minutes again to get it started. So I bought a used fuel pump ecu and installed it. The engine starts but immediately stalls out. So I used a paper clip again and bypassed the fuel pump ecu and the engine idles without stalling. As far as I know this proves the fuel pump ecu is bad, right?

I think constantly running the fuel pump in high speed for those two weeks may have worn out the pump. As long as the fuel pump computer is bypassed the engine runs, but it is misfiring. The engine was running fine until it stalled twice and this was while the fuel pump ecu was bypassed. So maybe the fuel pump is weak causing the misfire(s).

OG Dada

iTrader: (10)

There's no problem in bypassing the fuel pump ECU. A lot of People have did this as a permanent fix instead of buying a new one which costs $1xxx or a used one that might go out as well since this is a well known problem. As for the misfire check your spark plugs, wires and/or coilpacks, which is also known to go out in a power hesitation manner.

Lexus082

ok thanks. But if I bypass the fuel pump ecu by connecting the two pins with a paper clip and the car stalls when I remov the paper clip (jumper wire) that definately means the fuel pump ecu itself is bad correct? There's no possibility it would be something else. Thanks again.

luxryslide

im having a problem with my sc its not get fuel i just put in a new fuel pump and bypassed the ecu and put a new relay in but still not gettin gas anyone have this problem

DVSBSTD

Any resolution to this problem?

Ali SC3

iTrader: (10)

instead of bumping all the old threads about a fuel pump problem search for "fuel pump ecu" and you would have found the "12v fuel mod"