komar

iTrader: (1)

Hello,

Here is a brief summary of the problem, fixes and non fixes.... If anyone has a electrical manual for a 1992 SC400 i would love a copy of select pages.

Issue:
Key in ignition engine starter is engaged, engine turns over but will not fire. Problem is interment, and is hard to point what conditions cause the problem.

Fix#1, bypass the Fuel Pump ECU. black w/ red wire spliced to the Green wire powering the fuel pump. Fuel pump is activated as soon as the key is thrown to the "ON" position.

works fine for about 3 days. problem returns, the Fuel pump ECU is is not the issue.

The Black w/ Red wire is not getting power, the fuel pump is not activating when the key is "ON". No Signal means the ECU is not telling the PUMP to activate. Possible ECU replacment.

Fuse box (engine bay): the "EFI" relay is not activating/clicking with the key "ON". No Signal from INSERT NEED FOR ELECTICAL MANUAL.

Only when the issue is present doe the relay not work in the intended manor.

(basic lay out)
Port1 BATT PWR
Port2 GND
Port3 Signal in
Port4 PWR Out to EFI system, Read as ECU

Using a Jumper wire Key off i find jumping P1 and P4 the fuel pump activates, i start car and engine comes to life.

Findings:
Some where there is a break in the Port3 wire. need to know where that wire is coming from. Ignition switch? hence the need for a electrical manual.

has anyone had this problem?
1992 SC400 214K miles

thanks,
Kareem

Dx3

iTrader: (13)

Kareem,

Hope this helps





Jonny

attzor

iTrader: (1)

THIS! this is exactly whats wrong with my car, I did everything you did and had the same results, I hope there is a resultion in this thread.

komar

iTrader: (1)

Jonny,

thanks for the diagram. i will definitely post my findings over the weekend.

Kareem

komar

iTrader: (1)

Jonny,

do you have the wrest of the page saved as "ignition 1". the bottom is cut off, thanks

Dx3

iTrader: (13)

No problem man Yes, but it is at home and I'm at work. I will see what all I cut off tonight.

Jonny

tavarish

iTrader: (2)

PM me, I can send you the entire Factory Service Manual.

attzor

iTrader: (1)

Any progress? I really need to fix mine, I have it up forsale and I want to fix it before I sell it.

1siksc

iTrader: (8)

I had/Have this problem, the wire from the ignition isn't being activated, you can trace it from the relay to the Key, from the key to the source wire. Gonna try to fix it this year, but for now I have a battery cut off switch on my rear bumper and using a wire as a jumper.

EDIT: I have yet to fully look threw this so I am not sure if there is a security function in the way.

attzor

iTrader: (1)

So, If I wire the fuel pump to a switch, it will fix the problem for the most part? and is it hard at all if my battery is already in the trunk? Whats the name for the kit I need to do it?

komar

iTrader: (1)

still researching the wiring diagrams.

i need some pages with the "EFI MAIN" relay wires in and out.


right now, i have no idea what tells the EFI MAIN relay to turn on/ off. ECU or Ignition switch.

Any Local Sugarland area SC400 with a Spare ECU lying around? Pref a 1992.

Thanks
Kareem

komar

iTrader: (1)

PM'd you, please send over

komar

iTrader: (1)

UPDATE:
Looks like the ports @ fuse box in engine bay are getting voltage.
Port 3 is good to GND.
Port 2 is full power same as battery voltage.
Port 1 to NEG on battery as well as port 3 is not full battery power, but rather 10 volts...weird.
Port 4 is almost 0 Ohms to the ECU.
Ports 1,3 from fuse box to ECU show no breaks and almost no resistance.

This points me to the ECU, not sending enough voltage/amps to trip the relay. going to measure the amps across port 1 and port 3.

attzor

iTrader: (1)

It seems that my issue was just a loose wire in the trunk side of the fuel pump, I worked it a little bit and she fired right up. Don't you hate it when you spend so much time and money on something that is just as simple as a loose or frayed wire.

komar

iTrader: (1)

i need an ECU.

Till then i have added a key on powered wire power the relay.

Thanks for the help, to all.