Fuel Pump issue

[Steve]

I will try and explain this the best I can.

 

This is on Homers RSP car that we are putting back together, so far we have been unable to get the fuel pump working with the Fuel ECU.

 

We have tried with the link in the diag port in the engine bay (thus bypassing the Fuel Pump ECU), we should be seeing a continuous 12v at the pump, but with the connector plugged in to the top of the hanger the pump does not work.

I then tried unplugging this and using a multimeter see what voltage we are getting, it starts at 12v, but continuously drops, after 10-15 seconds it is down to around 7.30v and slowly still dropping. If you remove the multimeter from the connection, give it 30 seconds or so and re-connect the meter, it is back up to around 12v, but then starts to drop again. With it connected into the hanger again you don't get a voltage at all.

 

I have been looking over the wiring diagrams and it looks like the FP terminal in the Diag port is connected straight to the +'ve side of the pump. Between the -'ve of the battery and the B+ in the diag port is a steady 12v, so linking this to the FP terminal should give us a steady 12v at the pump.

 

Other than now checking those wires from the front to the back I am not sure what is going on with this.

 

Any ideas?

 

 

 

Wiring diagram can be seen on the attached PDF, page 8 for the fuel pump wiring.

wiring diagrams.pdf

[absz]

There is another connector plug between the fuel pump hanger and fuel pump ECU have you check the connections on that one. Its nearside in boot were the spare wheel sits

[Steve]

There is another connector plug between the fuel pump hanger and fuel pump ECU have you check the connections on that one. Its nearside in boot were the spare wheel sits

 

We have a new one which currently is laying in the boot until we get under the car to fit it properly

[Shane]

We have a new one which currently is laying in the boot until we get under the car to fit it properly

Had a very similar set of symptoms with one of my lads Imprezas and eventually traced it to a p!ug and socket issue in the main feed, on that car it was under the rear seat, but obviously it could be anywhere. Basically under load the connection broke down, off load it was fine and we had full voltage at the pump connector.

[Steve]

That will be the next thing to check really, each joint from front to back.

[Guest 2JZ GE W58]

i had a fuel pump calve 1 hr into my maiden voyage, it was seized. so i swapped over the pump out of my spare car. ran fine for a month then calved again.

i saw the 12v at the pump appear when ignition switched on (but not far enough to engage starter motor) and then drop off to a few volts too, i attributed this to be for the pump to prime up the line and then back off a tad until you start the engine and it goes back to 12v then.

 

anyhooo enough of the rant the problem turned out to be a connection in the plug on top of the pump hanger there under the spare wheel, beside the banjo bolt.

although it looked fine a connector blade was a shade bent off from me poking at it with a multimeter probe a month before when diagnosing the seized pump.

 

so theres something to check anyway, plug connections for solidness. see if you get the 12v which appears when ignition turned on then tapers off etc at the plug which goes onto the top of pump & work back from there

[Slutters]

High resistance somewhere, or a poor earth.

[Camry5Sgte]

I'd create a direct wire from ecu to the hangar. If the pump works then, you can safely say the fault lies in that section of the circuit.

[Steve]

Just to add to this after spending a couple of hours today going through the wiring.

 

All the wires check out ok back to the ECU and EFI 2 relay in the fuse box. The main ECU is sending the correct signals to the Fuel pump ECU via the DI and FPC terminals, there is power at the Fuel Pump ECU but the Fuel Pump ECU is not giving the output to the pump.

 

Also to add the Diag port override is not actually connected at all to the pump. It goes to the wing connector near the Main ECU but does not come out of there and along the wiring along the passenger sill. That pin and wire is not there at all so explains why the override isnt working.

 

So it just seems that it is the Fuel Pump ECU that is at fault

[Camry5Sgte]

Those pins on my diagnostic port are not there either. I found this out when my fuel pump went out on me. I couldn't use the override so I had to use power straight from the battery to the pump. Unfortunately, I don't normally carry that much wire and alligator clips on the road so I had to get her towed. Lesson learned, I carry my makeshift bypass now

[Guest Roger NE]

As per another thread, I'm currently trying to suss out exactly what the Fuel Pump ECU does . . . and what it's control signals from the MAIN Engine ECU consist of (this is because I'm fitting a 2JZ-GE in my Mk3, which has a much simpler relay-controlled fuel pump system)

 

The Mk4 Pump ECU obviously DOESN'T give full voltage to the pump all the time (which will actually be around 14V when the engine is running, not 12V) . . . on tickover it could be quite low . . . but I presume the voltage (and hence Pump speed) increases depending on engine load.

 

To bypass the Pump ECU you could, of course, simply power the pump from the main 12V feed from the ignition switch . . . so the pump is running whenever the ignition is turned on. But that is undesirable, as it would still be running if the engine stalled (in a bad crash you would really want the pump to stop!!)

 

I'm curious to know if one of the outputs from the MAIN Engine ECU could just drive a Relay coil to turn the pump on and off appropriately (so NOT use the Pump ECU).

[Guest Roger NE]

Still getting no response about what actually works in terms of by-passing the Fuel Pump ECU on any of the current threads about this issue . . . (of which there happen to be several at the moment)

 

I thought there would be more technical people on here who would be able to help . . .

[mellonman]

http://mkivsupra.net/vbb/showthread.php?272568-can-a-stock-fuel-ecu-run-a-400lph-pump-okay

 

Please read this link with a fuel bypass relay that keeps the fuel pump ecu safety features

[Guest Roger NE]

Appreciate you posting the link, thank you

 

But the problem is the mod that guy has done still relies on the Fuel Pump ECU to be in place AND working . . . all it does is use the original Fuel Pump output voltage to feed the coil of a new relay, and that relay then feeds the full 12/14V supply rail to the Pump.

 

As someone has then posted in that thread, the problem is that if the Pump ECU fails completely, that relay won't even operate . . so no Fuel Pump operation!

 

What would be better would be to NOT use the Fuel Pump ECU AT ALL . . . so it is properly by-passed.

 

But has anyone sussed out what the two signals from the Main Engine ECU to the Fuel Pump ECU actually give? Or has anyone found the circuit diagram for what's inside the Fuel Pump ECU? (probably only a couple of transistors)

Edited November 12, 2013 by Roger NE (see edit history)

[Steve]

IIRC the FPC wire (Purple/White) from the main ECU just gives a 0v feed when turned on, so this could be used to fire a separate relay which control the power to the pump which.

[mellonman]

Appreciate you posting the link, thank you

 

But the problem is the mod that guy has done still relies on the Fuel Pump ECU to be in place AND working . . . all it does is use the original Fuel Pump output voltage to feed the coil of a new relay, and that relay then feeds the full 12/14V supply rail to the Pump.

 

As someone has then posted in that thread, the problem is that if the Pump ECU fails completely, that relay won't even operate . . so no Fuel Pump operation!

 

What would be better would be to NOT use the Fuel Pump ECU AT ALL . . . so it is properly by-passed.

 

But has anyone sussed out what the two signals from the Main Engine ECU to the Fuel Pump ECU actually give? Or has anyone found the circuit diagram for what's inside the Fuel Pump ECU? (probably only a couple of transistors)

I see there was a guy that put a 2jz in a hilux that done a diagram and made one I will try and find it

[Guest Roger NE]

IIRC the FPC wire (Purple/White) from the main ECU just gives a 0v feed

Actually it gives a PWM (Pulse Width Modulated) signal to the Pump ECU . . . which then has circuitry that decides how much voltage to give to the Fuel Pump, depending on engine load.

 

How do I know? I've just managed to find the info on this website HERE

 

It not only explains what the two output feeds from the 2JZ Engine ECU to the Fuel Pump ECU actually are, it even gives a suggested circuit diagram to replace the Toyota ECU with a full voltage relay system (although there's nothing special about that circuit, or anything critical about any of the components)

 

Excellent ! So if I can't get hold of a Pump ECU for my engine swap, I shall be building my own module to feed the Fuel Pump I think.

Edited November 12, 2013 by Roger NE (see edit history)

[mellonman]

http://mkivsupra.net/vbb/showthread.php?276099-Hi-2JZ-Hilux-Pics-amp-problems&highlight=hiluxope this helps also

[Guest Roger NE]

Yes he obviously found the info on the same website as I did !

[Guest Roger NE]

Been thinking about this some more . . .

 

I've no experience of DC Motor control . . . but I remember reading how modern model railway power supplies use PWM to reduce the speed of the train, rather than just reducing the voltage, as giving it a pulsed full voltage but with reduced duty cycle means the motor still has full torque, but runs at a lower speed.

 

That being the case, I would have thought that Toyota WOULDN'T convert the PWM signal from the Engine ECU into an Analogue variable DC voltage . . . surely they would just use it to pulse on and off a Power Transistor in series with the Fuel Pump Motor?

 

In other words perhaps the fuel pump maybe ALWAYS gets full voltage . . . but it gets different width pulses, depending on the speed the ECU wants it to run. (of course, if you try and measure the voltage with an ordinary meter, you will just get an average reading . . so if it's getting a 50% duty cycle signal, it would measure HALF voltage)

 

Can anyone confirm whether this is the case?

 

(I'm sorry I can't confirm this myself either way, as I don't yet have a running 2JZ engine!)

 

But if this IS the case, it would explain why anyone trying to understand voltage measurements taken on the Fuel Pump wouldn't really make sense, unless you used an oscilloscope.

Edited November 13, 2013 by Roger NE (see edit history)

[Homer]

On 11/10/2013 at 4:29 PM, Steve said:

Just to add to this after spending a couple of hours today going through the wiring.

 

All the wires check out ok back to the ECU and EFI 2 relay in the fuse box. The main ECU is sending the correct signals to the Fuel pump ECU via the DI and FPC terminals, there is power at the Fuel Pump ECU but the Fuel Pump ECU is not giving the output to the pump.

 

Also to add the Diag port override is not actually connected at all to the pump. It goes to the wing connector near the Main ECU but does not come out of there and along the wiring along the passenger sill. That pin and wire is not there at all so explains why the override isnt working.

 

So it just seems that it is the Fuel Pump ECU that is at fault

Dragging this topic back out of the archive. Since Steve posted this update I’ve tried 3 different Fuel Pump ECU’s and all have the same result. Steve did create a bypass for testing but it resulted in the pump being on even with the key our of the ignition. 

So, we know the pump works, we know at least the power wires to the pump are good, but the pump Ecu is not getting an ‘on’ signal from either the Ecu or there’s a break somewhere else.

Any ideas folks?

 

[Swampy442]

Looks like you've diagnosed your own fault to me, if the ECU isnt sending an on signal theres your problem

 

[Homer]

3 hours ago, Swampy442 said:

Looks like you've diagnosed your own fault to me, if the ECU isnt sending an on signal theres your problem

 

Sorry for not being clear. As Steve mentioned before the FPC and DI are sending ‘a’ signal to the fuel pump ECU, however the fuel pump Ecu is not turning the pump on. At first this was expected to be a faulty FP Ecu, but this has now been ruled out. 
 

Does anyone know if FPC and DI are constant voltage feed (or even if they are feed or return signals) from the ECU or is it a modulation signal? These are pins 21 and 22 on the E10 block connector.

Steve rigged up a bypass that’s uses FPC as a trigger but it’s inconsistent (sometimes pump on, sometimes off).

Example: Ecu is reset. Battery is reconnected, pump is off. Turn key to ‘2’ pump is on. Fire engine and it runs. Turn key to off and remove key and the pump is still on! 
Disconnect battery, reset Ecu, next time the battery is reconnected the pump is on right away even with no key in the ignition.

[Homer]

Possibly found an explanation for the signal so this is just for future reference and note to self: 

Engine ECU FPC & DI Pin Operation

The engine ECU outputs a 0V to 5V Pulse Width Modulated (PWM) signal on the FPC pin which is connected to the Fuel Pump Control ECU to control the speed of the fuel pump.

 

The Fuel Pump Control ECU also has an output to the engine ECU that indicates that the Fuel Pump Control ECU is healthy.  The output from the Fuel Pump Control ECU connects to the engine ECU pin labelled DI.  The Fuel Pump Control ECU connects the engine ECU DI pin to battery voltage when the Fuel Pump Control ECU is healthy. 

 

It is worth noting that at least on some engine ECUs that if the engine ECU DI pin is not connected to battery voltage then the engine ECU will stop the PWM output on the engine ECU FPC pin which will then signal to the Fuel Pump Control ECU to turn the fuel pump off.