Desacatao

Hey guys im new on CL and i own a 2000 Lexus GS400 . Also i am glad to join the community , Soooooo i have this problem that my fuel pump wont turn on , now i have replaced it with a new one , i have replaced the efi relay , i have replaced the fuel fuse , i have checked the fuel pump controller and it has power to it and also the fuel pump connections and also am getting power to that . Can some one tell me what am i missing ?
Thnks in advance .

sbagdon

Is the fuel pump being told to turn on?
If so, is the fuel pump receiving that signal?

Desacatao

how can i know if the fuel pump is being told to turn on . i know the fuel pump controller is working because it has current but im not sure if its actually telling it to turn on .

sbagdon

Just because the Fuel Pump ECU has power, doesn't mean the Fuel Pump ECU is working. That's like saying a radio has power, yet why won't it turn on.

Are you receiving a P1200 on your ODB-II scanner?

'98 FSM for 1U (hope this applies...!), SF-81... Fuel Pump ECU. Kinda hidden back there, in the trunk. SF-82... inspect ECU, refer to DI-281.

DI-282. #1... does the fuel-pump run? On the fuel-pump connector, apply 12V+ to terminal 4 and 12V- to terminal 5 (for no longer then 10 seconds!)... does the fuel pump run, and does it produce 44-50psi of fuel pressure? If so, you know the fuel pump is ok. If not, replace the fuel pump.

DI-282 #2... is the Fuel Pump ECU receiving power? Disconnect ECU, turn ignition ON, and check ECU terminal 10 and body-ground, for 9v-14v.

DI-283 #3... on Fuel Pump ECU, check voltage between pins 5 (V-) and 8 (V+), while ignition switch is turned to START... should be 3.3v-4.3v. That says that the ECM is sending a fuel-pump high-speed order to the Fuel Pump ECU. If no, sounds that the ECM isn't outputting a signal, and you have ECM issues. If yes, then the Fuel Pump ECU is getting its signal to turn on the fuel pump.

DI-283 #4... Check for open and short in harness and connector between terminals FPC of ECM and 8 of fuel pump ECU, terminal 5 of fuel pump ECU and body ground. Can everyone talk to each other?

DI-283 #5... plug the Fuel Controller ECU back in, and set the ignition to START... is the fuel pump getting battery voltage (12v-14v) from the Fuel Pump ECU ... if yes, then pump. if no, then harness.

Have fun.

Desacatao

thanks will try to do all this tomorrow , i also have a mechanic coming out tomorrow to do it for me since he has all the tools i dont . but while i wait for him i will try and do my best at what i can do .

TrueGS300

Wouldn't it be easier to just use a test light at the fuel pump module and see if it lights up on key-on and crank first?

Desacatao

Now i am lost on whats a ECM . im fairly new on this type of stuff specially on a GS .

sbagdon

Yes.

From the DI section of the FSM, appears the pumps static-state is off, with high-pressure occurring during START and high-load (then there's medium-load, light-load, and no-load). Ah, the days of... it's on, or it's off...?

Engine Control Module (usually applies to all vehicles).

Ah, the good ol' days... when you'd just turn the car to ON, and you'd hear (or not hear) the fuel pump run for a second... then check pressure at the fuel rail for 45-50psi.

Desacatao

im having a mechanic come check out the car tomorrow if the weather holds up because what i have diagnosed i honestly cant do any further reason being that i dont have the required tools or wires to do so but i appreciate all the info and help , will keep you guys updated

Htony

Replacing parts does not solve the problem. Trouble-shooting does. Don't you have a simple DVM?

Desacatao

DMV ?? what is that , and i know it was my mistake on doing that but i didnt have the tools to check what it was and i just resulted on changing the fuel pump first then the fuel pump relay and checked the fuse , i wasnt really finding any online that would direct me to the problem but other than trouble shooting what i replaced but i just ended up contacting a mechanic to come out and diagnose my car for me since i dont have the rest of the proper tools or acknowledge to do it my self , but again i appreciate all the help im getting from you guys glad i did join this forum

Htony

DVM = Digital volt meter. In some cases ECU won't allow to activate fuel pump under certain circumstances such as car is crashed for an example to minimize the
possibility of fire breaking out spilling fuel. Is there any CEL(check engine light)? Then that will be the clue fetching DTC(diagnostic trouble code) I guess checking
voltages from fuel pump backward to find where is the source of problem. You may need a schematics to trace wires in the related wiring harness.
Trouble-shooting is a logical process of elimination step by step. Check one part >> good or bad?, check next part >> good or bad? Until you reach a part where the
trouble is. Good luck.

Desacatao

My CEL has been on over a yr now , i have more light on after my ball joint popped out on me but never had this problem before . i forget what are the code for the CEL light but its nothing leading towards the fuel pump but im going to hopefully get it checked tomorrow by a mechanic and i hope we find the problem , now i did the basic process of elimination but someone said even if the fuel pump connection is getting power it doesnt mean the fuel pump controller is actually working which im not to sure how to check that it self i check the plug and its giving out enough vlts but still not completely sure , but deff will keep you guys posted and again appreciate all the help and information i am getting .

sbagdon

Believe fuel pump and fuel pump ecu should throw P1200.

Desacatao

if my mechanic comes by tomorrow i will see if thats the code that it gives him because honestly i have been stressing so much from this .