Retox

Hey all... I'm having problems with my vehicle (91 Toyota Soarer - Basically its a Lexus SC300 with a factory fitted 1JZGTE) refusing to start.

Have checked ignitor, injectors and plugs... all ok there.

Have isolated the problem back to the fuel pump. With everything all plugged in normally, there is no power to the pump.

with the FP and +B bridged in the diagnostic port, I am getting 7.5v to the pump.

there is 12v coming in to the fuel pump ecu via the Red/Blk wire.

I bridge Red/blk with green on the harness from the fuel pump ecu, and only get 8.5v at the pump.

The fuel pump ecu is working, as it has been tested in another vehicle.

Now, there are 3 other wires (aside from red/blk and green which I mentioned) into the fuel pump ecu... an earth, and two others which come from the main ECU, so obviously the main ECU takes data from some relevant sensors (god knows which) and uses that data to send info to the fuel pump ECU which inturn controls voltage to the pump.

My first question is: What could be causing the fuel pump ecu not to send power to the pump?

My second question is, if I remove the fuel pump ECU, and run the Red/Blk wire direct from its harness to the fuel pump, will this cause problems, and will the main ECU put up any error messages if I do?... The red/blk wire will be fine to do this, as it already fused and on a relay.... but will having the pump running on constant 12v cause any probs?

All connections to the main ECU are firm and secure as well if that crosses anyones mind.

Would REALLY appreciate some quick advice on this.

Thanks in advance

mitsuguy

iTrader: (2)

you can bypass the fuel pump ecu - just search the forums, there are a couple DIY's about how.... the only detriment here is that the fuel pump will run full tilt 100% of the time - not necessarily a bad thing performance wise, but it will decrease the life of the pump a little...

it sounds like the fuel pump ecu is doing its job correctly... the engine control unit tells the fuel pump ecu to ramp up voltage at a certain rpm...

you will not receive any error messages related to bypassing the fuel pump ecu...

Unless the fuel pump is not working properly, I believe your problems lie elsewhere...

it is perfectly normal to only get around 8 volts to the pump unless the vehicle is at higher rpm

Retox

Right, so if the ECU is not sending the signals to the FP ECU, then what could be driving that?

Screwed sensor, if so which one maybe?... or could it be the ECU itself?

mitsuguy

iTrader: (2)

assuming the ecu is good;

crank position sensor... (ckp)

but if the ckp is not working, a fuel pump is the least of your issues, as it won't fire spark plugs or fuel injectors either...

I think I may be able to give you some more insight with more information here...

It doesn't start - does it crank strong? I know you say you have checked injectors and spark plugs, but how? have you checked fuel pressure???

Retox

Sorry, I thought I had covered those points, my mistake

Cranks well.. new battery makes certain of that
Spark - Yes, all plugs checked and cleaned
Injectors - Yes, multimeter put over all of them and all are alive
Fuel Pressure - Without power to the pump, there is none.

mitsuguy

iTrader: (2)

But there is power to the pump... you said 7.5-8.5 volts... this is correct given low RPM (as in cranking / idle would present)...

To find out if fuel supply is truly your issue, you need to get a fuel pressure gauge on the fuel rail and see if while it is cranking that fuel pressure jumps up to around 40 psi... if it does not, then we are looking in the correct area, but, if fuel pressure jumps, then it is not the fuel ecu or pump...

Retox

The only time I can get power to the pump is either bridging the diagnostic port, or bridging the FP ECU loom.

mitsuguy

iTrader: (2)

bad ecu...

need to check two things before we confirm though... when the key is first turned to the on position, the ecu will energize the pump for a quick second to make pressure... after that, it will stop and not energize until it sees the vehicle cranking...

what you need to do to confirm a bad ecu is to put a voltmeter on the output from the ecu to the fuel pump ecu, and also one from the fuel pump ecu to the fuel pump and see if there is a quick voltage spike right when the key is turned on...

also, we need to confirm that the engine ecu has power and ground...


if the ecu has power, but no voltage spike from the ecu to the fuel ecu, then about the only thing that can cause your issue is a bad ecu... I truly can't think of anything else, as there are no sensors that control this stuff, especially pre-start...

Retox

I'll give those things a go... thanks

Retox

oh... and if I dont reply beforehand with an outcome... Merry Xmas

Retox

well, a friend came over with his spare ecu... we put that in... nothing.

I'm giving up on fixing this problem now, I'm just going to get all new wiring and relays for the pump put in, completely bypassing Toyota's retarded over-complicated bull**** system.

Thanks for your help though

mitsuguy

iTrader: (2)

no problem... you know... if you want a quick test, just jump +12v to the pump and try starting it and see what happens...