Fuel Pump Control

[Guest Roger NE]

Has anyone ever sussed out how the Fuel Pump operation on the 2JZ varies according to driving conditions?

 

The reason I'm asking is that I'm replacing my 7M-GE with a 2JZ-GE in my Mk3 Supra (MA70)

 

The MA70 just has a simple relay control system for the Fuel Pump - full voltage on cranking and full engine load, lower voltage (through a resistor) for all normal running, and turned off (via a switch in the AFM) when the engine is drawing no air, so presumably off on Overrun, or if the engine stalls.

 

I have now realised that the JZA80 has a separate Fuel Pump control module . . . so I wonder how much that VARIES the voltage fed to the Fuel Pump (and hence speed) ? If it uses a power transistor in that module, I guess it has the capability of being continuously variable, depending on fuel demand - Has anyone ever sussed this out?

 

For example, does the pump run slow on tickover, but speed up when accelerating?

 

The problem is that I can't even make my fuel pump run like it's designed to in the MA70, as there will be no commands from the AFM . . . so do I just run it all the time the ignition is on . . . or would it be worth my getting hold of a JZA80 Fuel Pump control module?

 

Would welcome opinions . . . .

Edited November 11, 2013 by Roger NE (see edit history)

[David P]

A T.T. f.p. ECU is a stronger unit than N/A and wiring same, diagram here.

 

http://www.mkivsupra.net/vbb/showthread.php?298998-Fuel-Pump-issue

[Guest Roger NE]

Can't see any diagram in that thread . .

 

And how do you mean STRONGER? And surely a TT engine has different fuelling requiremnts to an N/A, so it may work differently.

 

But my main question is HOW MUCH does this unit actually VARY the voltage applied to the pump? Does anyone know?

 

If it just gives a steady voltage all the time, then I might as well just use the relay system already on my MA70.

Edited November 10, 2013 by Roger NE (see edit history)

[Benjy]

I think you'll find the fuel pump module/ecu is required as the main ecu won't switch the pump on until it gets a signal/request from the pump ecu.

[Guest Roger NE]

the fuel pump module/ecu is required as the main ecu won't switch the pump on until it gets a signal/request from the pump ecu

 

I realise that . . . but I can simply wire it so the pump is running with a constant voltage all the time the ignition is on.

 

It's just whether people think there's any real disadvantages in doing that?

[Steve]

Yes, if the car is involved in an accident there is the chance if it is wired like that the pump wouldn't shut down and just continue pumping fuel.

[Guest Roger NE]

Well one thought would be to plumb a Vac switch into the Intake, which would cut the pump relay if there was no Vacuum . . . in that way the pump would stop if the engine stopped. (think I already have a suitable one from when I removed my EGR system)

 

I guess nobody on here knows whether the voltage fed to the pump by the Pump ECU actually varies much?

 

(if it DOESN'T, I might as well stick with my simple MA70 relay system)

Edited November 10, 2013 by Roger NE (see edit history)

[David P]

Can't see any diagram in that thread . .

 

It's only in post 1.

[Steve]

Well one thought would be to plumb a Vac switch into the Intake, which would cut the pump relay if there was no Vacuum . . . in that way the pump would stop if the engine stopped. (think I already have a suitable one from when I removed my EGR system)

 

I guess nobody on here knows whether the voltage fed to the pump by the Pump ECU actually varies much?

 

(if it DOESN'T, I might as well stick with my simple MA70 relay system)

 

 

IIRC it runs 9v under light load then goes full 12v+ under high load.

[Guest Roger NE]

Just found that attachment at the bottom of Post 1 - but I've already studied the Circuit Diagrams! That's how I came to the conclusions I have (plus as far as I can see the circuitry is the same for Mk4 N/A and TT models)

 

In the Mk3 the pump is fed by a couple of relays . . . it gets current through a Resistor for normal running (so think it gets about 8V) . . . however on engine load and cranking a signal from the ECU operates a relay that shorts out the resistor so it gets full voltage.

 

Would be useful to know how people have done 12V Pump mods on their Mk4s . . . that might give me a clue how I can interface the two systems WITHOUT using the Pump ECU

Edited November 11, 2013 by Roger NE (see edit history)

[Guest Roger NE]

I've seen people mention doing a Mod to by-pass the Pump ECU to give it full voltage all the time

 

Is there a Guide for this anywhere? (done a search, but can't find anything)

 

It would be useful to know if the main ECU has an output that can turn the pump on and off appropriately (albeit through a relay)

[Guest Roger NE]

If nobody can help with that, can somebody describe what the Fuel Pump ECU looks like? (it's from an N/A , if they're different)

 

I gather from the diagrams it's fitted near the rear left hand wheel arch - but remember, I don't have a Mk4 to look at!

 

(someone thinks they may have a spare one, but they don't know what it looks like)

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

[Guest Roger NE]

I've now sussed out exactly how the Fuel Pump ECU works, and what command signals it gets from the main Engine ECU (as per my post on another thread)

 

But I'm still hoping someone can tell me exactly what the Fuel Pump ECU looks like ! (someone has a load of modules from a scrap car, but doesn't know which is which)

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

[Guest Roger NE]

Many thanks to Dazzi for identifying the Fuel Pump controller . . . . and offering me one very cheap !

[Dazzi]