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

Gspec

Bypass the fuel pump ecu by joining the 2 larger gauge wires together at it's plug.

Ali SC3

iTrader: (10)

I have mine bypassed. to retain safety functions you can use the voltage coming out of the ecu as a trigger to a 12v automotive relay.

GSXRMack

iTrader: (3)

Are you on the original pump? If so might be time for an upgrade.
If you keep it bypassed definately run a relay.
To 100% rule out the FP ECU did you run the other persons FP ECU in your car?
Last things. I assume the starter turns over?
When the factory alarm gets into anti theft it kills fuel and the starter. Has your battery died lately?
Good luck.

Retox

Thanks for the replies!

To answer in order -

G-Spec: Have done that, but by doing so only get a reading of 8.5v at the pump. Not sure why I am getting a 3.5v drop between that plug and the pump. I wonder that if by doing this, will I run the risk of having the mix lean out as the pump cannot supply the full flow needed in high demand situations that a 12v current is needed for? (hope that makes sense)

Ali: Not sure if I follow what you mean there, I'll show this topic to the person helping me out, he should know what you mean.

Sven: Factory pump at the moment. Will be looking to upgrade to a Walbro GSS... figure now might be the best time to do that as the factory turbo system has been swapped for a single Garrett GT35-82R. I had taken my FP ECU out and over to a friends place and into his vehicle, started and ran perfectly every time for the 3 or 4 times we ran it to test. Starter turns over, plenty of spark, power to all injectors.
Battery has died lately, but vehicle does not have a factory alarm system.

Ali SC3

iTrader: (10)

What I was saying is just another way to do the fuel ecu bypass, but safely.

after reading what you wrote above it seems you are saying that when you took the 12v red/black going into the fuel ecu and connected it to the power wire going to the pump, you are only getting 8.5v at the pump?

if thats the case then that is not a good sign. there should not be that much of a drop. make sure when you connect these two wires at the fuel ecu connector, that you do not plug in the connector to the fuel ecu. you should have the voltage of the red/black wire all the way to the pump, or you have a bad connection somewhere. if you measured this value with the car off then that could explain some things as the voltage will be lower with the car off. 8.5v sounds like your fuel ecu is still in the mix. in the simple bypass method it should be disconnected.

now there is another way to do it which can eliminate any stock wiring issues. basically you run a 12v from the battery (or other 12v location) to a relay (switch basically) and then run it to the pump. then you use the output of the fuel ecu (the one which previously went to the pump) to turn on the relay. so basically you are using the old fuel ecu output as a light switch to your new 12v line. this is different because it still retains the ability for the fuel ecu to turn the pump on and off in emergency situations or when you are just sitting with the engine off.

the original way with just bypassing the fuel ecu without a relay makes it so your pump is always on with the key in any position other than off. even when you do move the key to the off position the pump keeps going for like 5 seconds or so (like cars from back in the day).

Retox

That’s right, plug removed from FP ECU, inward current on rd/blk tested at 12v. Paperclip bridge in FP ECU loom from rd/blk to green, and then tested at pump as 8.5v being delivered to pump. I do note from a seperate plug at the rear of the tank (where the fuel sender is) there is 4 wires coming into this plug (2x green, 2x wht/blk), the other side of the plug then has the blue & white wiring going over the tank and to the pump.

These additional wires (which are a factory fitment) I could only assume come directly from the diagnosis port, as I’m sure this is what allows it to bypass the FP ECU when bridged. If that is the case, could that possibly explain the voltage drop as it is feeding current all the way back to the engine bay again? (brainstorming here, correct me if I am wrong)

With respect to your other way of doing it, I can see how that may work in theory, however with the FP ECU plugged in I am not getting any current from it to the pump (whether this is caused by the main ECU or a sensor that it reads from which inturn gets sent to the FP ECU, who knows!), so I cant see how this would work in the current circumstance, as if there was a current coming out of the FP ECU in the first place, I would be getting a reading back when the multimeter is put on the connections at the pump. Or am I misunderstanding you?

Tracing the rd/blk wire that feeds 12v into the FP ECU, this is already going via a factory relay and fuse, so I think it should be suitable for re-routing directly to the pump if I’m not mistaken. Again, please correct me if I am wrong

Wiring Diagrams here if you need to refer to them:

http://web.ukonline.co.uk/soarertt/s...ne_control.htm

GSXRMack

iTrader: (3)

No alarm then that idea is out.

Best bet since you have upgraded the turbo is to now make the jump.
-New fuel pump
-Relay

And follow Ali SC3's way of hooking it all up 8.5 volts should be enough to get the relay going and still be safe.

Retox

Hi Sven,

Relay has been checked, it works fine (removed it from fuseboard, put it back in again while accessories power on, made switching sound as soon as terminals made contact back with the board)

Fuel Pump - that works, once power was bridged from rd/blk to green on FP ECU plug, pump primed (fuel line disconnected before fuel filter to confirm this, line was flowing)

I'll get the old man to check out Ali's post... I'm pretty sure I havent grasped it properly with my response above. Dad being an ex-sparky knows a lot more about this and will probably clue on to it a lot better

Retox

Been looking more at this... and my thoughts are, if I do this wiring setup its still not going to work anyways because there is no power coming out of the fuel pump ecu (green wire) which means nothing will trigger the relay.

What i need to find is what the hell is preventing a signal being sent from the main ecu to the fuel pump ecu to allow it to operate.

All this looks like a classic case of fuel pump ecu being fcuked... however I reiterate that it has been tested in another vehicle and works perfectly.

******* toyota and their retarded fascination for overcomplicating even the simplest of things!!!!