fuel ecu problem, I think

[michael]

Hi I am in need of some serious help. I just bought a sc400 1992 and just had my first problem, my second is I don't have the money to pay the dealer so I'm hoping I can get a quick fix here and head to the salvage yard.
My car is stalling when I start it. Engine cranks up and then stalls within a few seconds. If I give the car a quick throttle boost at start up to 3000 rpm and then let off the gas the car will idle and drive perfect, no issues at all after start up, until I try to start it regurally next time. It stalls on regular start up when cold and when hot. I'm tired of giving it gas at start up, has anybody any clues or suggestions, I would like to fix tomarrow, thanks. mike:wtf:

 

[Lextreme II]

I am not an expert but could this be a cold start injector or possible fuel pump relay or ecu.

 

[Peewee]

Bridge FP and +B in the diagnostic box on the front of the motor before you try your next cold start.

Then quickly go from OFF to START, do not let it sit on ON for more than half a second (otherwise the test wont work).

If it starts perfect then, try it a few more times over the next few days.

The bridge between FP and +B bypasses the Fuel Pump ECU.

If you don't have any issues with the starting now, its most likely your fuel pump ecu.

If that doesn't fix it, it could either be your cold start injector (not enough fuel), or even your idle speed controller (not enough air).

 

[michael]

People are telling me it's most likely the idle motor. I don't know, this has so much sensor electrical bullshit atatched to it. I swapped the mafs , I also swapped the fuel ecu , I'm totally frusterated. I have to take it to the dealer.

 

[Nick M]

I swapped the mafs , I also swapped the fuel ecu , I'm totally frusterated. I have to take it to the dealer.
Yesterday 09:26 AM

Imagine how much money you would have saved if you went straight into Toyota(Lexus) and not put time into air flow meters, which dont cause your symptoms, and a processor. There isnt a fuel only ECU. Time is money afterall.

 

[Nick M]

Do you know how to pull DTC's?

 

[michael]

I was told that the fuel ecu was directly behind the drivers seat in the back seat area right under the window, this was the electrical box I swapped.

And no I don't know what dtc's are? Thanks for your reply.

 

[mycarhasposessedme]

There is a fuel pump ecu.

 

[Peewee]

I was told that the fuel ecu was directly behind the drivers seat in the back seat area right under the window, this was the electrical box I swapped.

And no I don't know what dtc's are? Thanks for your reply.

You have an SC400 so yes, you HAVE a fuel pump ecu right there.

My method above will help diagnose it, but if you have already swapped in another then its obviously not the cause.


NickM, you are right in saying the car does not have a fuel only ecu, but this is what what we mean. The SC400 and the later LS400's have a FUEL PUMP ECU. Its just a PWM module that controls the voltage going to the fuel pump. Just to keep the noise down at idle.



DTC's are diagnostic codes. Do a search of the forum and you'll find out how to retrieve them.


With the idle speed controller, its the round black thing at the front of the intake manifold (under the L badge).
Its held on by 3 phillips head screws.
Take if off, and clean it with carby cleaner/throttle body cleaner, get it looking shiny again. Clean the bit where it goes in too.

Probably will take a couple of hours to do it the first time.

 

[sideshow]

fuel pump ecu is i think on left hand rear quarter

u pull the trim away in the boot on the left hand side

and run yr hand behind the metal panel somewhere there

its called a fuel pump ecu cause it takes the signal from the engine ecu and reads it and turns the pump on

then if controls the voltage thru a secondary wire from the engine ecu

i have a 2nd hand one for sale if u want one

 

[Peewee]

fuel pump ecu is i think on left hand rear quarter

u pull the trim away in the boot on the left hand side

Between the B and C pillars
Next to the rear left passenger.

 

[Roger]

fuel pump ecu

I am experiencing some problems with my V8 Soarer. I think it was Michael who had a similar problem the engine cranks over but doesn't starting. Acting like it is starving for fuel. I bypassed the fuel pump control ECU by bridging Fp and +B on the engine diagnostics port and the fuel pump runs. I put in a new fuel pump control ECU and the engine ran beautifully. Drove for about 15 KS and then the same problem all over again. What on earth could be the problem?? Any help out there.

 

[Roger]

Mike
How did you go with your engine problem. My V8 Soarer does something similar. I have changed the fuel ecu and it worked for awhile then the same problem. What did you do in the end
Roger

 

[Peewee]

Try cleaning the idle speed controller

 

[sideshow]

well u have to work it out backwards

start at the fuel pump and work back with a multimeter

i can tell u to change parts but might be expensive

doesnt anyone there know how to work on these cars

i can usually work it out in under an hour but its bit far for u to bring car to me

theres about 2 or 3 relays which have some control on ecu then you have the fuel pump ecu

so get a multimetr and start testing

or take it to someone

its very hard prob to solve on here

put a test light on the power wire to pump and if it has power and car stops then its prob yr fuel pump

theres is prob 20 spots that can play up

 

[Roger]

thanks i will do all the above, appreciate your help.
Roger

 

[Nick M]

Did you find out how to pull DTC's?

 

[Roger]

No How do you do it??

 

[Roger]

I pulled out the idle controller. Was dirty O cleaned it and will put new bearings in on Monday. Tested with an ohmmeter OK.

 

[Peewee]

Steps for diagnostic code retrieval are written all over this forum.

Give it a good read, I know I've personally typed it out step by step at least half a dozen times.
I really should just keep it handy so I can cut and paste it when required.