R32 Fuelpump Speed Controller

[B0oStEr]

I'm about to fit an bosch fuelpump and I'd like to know how the factory system works before I try to improve or bypass it.

What components are involved in it's operation and where are they located? ECU pinouts? TPS? resistor, relays etc

A circuit diagram or a link to a manual that covers it would be great.

[browny]

Based on the wiring diagrams and the service manual (ie i've never actually pulled one apart) all the stock system appears to do is switch a resistor inline with the pump, thereby dropping the pump voltage. This is controlled by a signal wire from the ECU.

Not sure exactly what the ECU uses to determine when it should be at "low", possibly neutral switch or idle switch or both?

I can look up more when I get home.

[B0oStEr]

Based on the wiring diagrams and the service manual (ie i've never actually pulled one apart) all the stock system appears to do is switch a resistor inline with the pump, thereby dropping the pump voltage. This is controlled by a signal wire from the ECU.

Not sure exactly what the ECU uses to determine when it should be at "low", possibly neutral switch or idle switch or both?

I can look up more when I get home.

<{POST_SNAPBACK}>

Thanks champ, some more details would be great.

Is your service manual a book or CD?

[BH_SLO32]

B0oStEr,

Assuming you have an R32 GTST the ecu activates the Fuel Pump Control Modulator (FPCM) when the engine is cold. In essence the FPCM is just a switch which is earthed when the engine is cold. The FPCM is wired in parallel with the resister pack located in the engine bay on the left strut tower (adjacent to the turbo).

Basically it reduces the resistance downstream of the fuel pump when cold allowing a greater current flow and hence pressure for cold conditions (acts like cold enrichment). Once warm the FPCM circuit is open resulting in reduced current flow and hence fuel pressure.

According to the wiring diagram the non-turbo R32's don't have an FPCM but also don't have the additional resistor in line with the fuel pump. The fuel pump resistor is about 0.8 ohms.

If you disconnect the fuel pump resister (in the engine bay) and start the car when cold it should run fine whilst the FPCM is activated. Once the FPCM is switched off (when warm) the car will stall because the parallel circuit with the fuel pump resistor is also open circuited.

Please note the above applies at idle but haven't tested above idle. The GTRs operate differently again.

The above applies to R33 GTSTs but the location of the resister pack and possibly the FPCM is different. Again not sure what happens above idle.

Hope this helps.

Edited September 2, 2005 by BH_SLO32

[Cubes]

Its also interestering to note that when you fit the PFC up it no longer uses the high/low.

Its always on high.

[PlasticStan]

Its also interestering to note that when you fit the PFC up it no longer uses the high/low.

Its always on high.

<{POST_SNAPBACK}>

Still have two stage fuel pump voltage on mine with a powerFC, can hear the pump speed up when you open the throttle.

[browny]

BH_SLO32 is on the money. Only thing I would add is that the FPCM also appears to switch in when the engine is under load.

[B0oStEr]

Browny

Do you have a wiring diagram showing wirre colours?

[Cubes]

PlasticSan,

Your PowerFC is a R32 AP Engineering?

I 100% no longer have the 2 stage highlow. For example when idling then touch the accelerator.

I can always hear the fuel pump on high, plug the stock ecu back in and I've got the 2 stage back.

Strange.

EDIT: I've just had a quick look to try and track down what car you drive. It appears to be an R33, so.. Not an R32.

Edited September 3, 2005 by Cubes

[MonstaS4]

B0oStEr,

......Basically it reduces the resistance downstream of the fuel pump when cold allowing a greater current flow and hence pressure for cold conditions (acts like cold enrichment). Once warm the FPCM circuit is open resulting in reduced current flow and hence fuel pressure.

<{POST_SNAPBACK}>

I was under the impression the fuel pressure reg. controls fuel pressure. By increasing/decreasing the voltage across the pump, the FLOW capacity of the pump would increased/decreased. I'm not sure why it would be increased at idle because the coolant temp sensor combined with the ecu would increase the injector pulse width. Obviously the pump will speed up under load to increase the fuel available to the injectors

[AntonRx7]

where did you guys get the servie manual for a r32 GTST from? i have been looking for one for ages

[B0oStEr]

It's my understanding that the fuelpump speed control switches the pumps earth from direct to the chassis to earth through the resistor so that it reduces pump speed and noise when full capacity isn't required eg at idle and possibly at cruise.

If the pfc in the r32 doesn't operate the speed control then the decision to ditch it has been made for me.

All I need to know is how to wire my 040.

Should I run a new earth from pump directly to the chassis?

Should I upgrade the power wire by using a relay and running a new wire from the battery?

[browny]

where did you guys get the servie manual for a r32 GTST from? i have been looking for one for ages

You can buy them online from the guys who translated them: http://www.jpnz.co.nz

I think there are some aussie distributors as well.

It's my understanding that the fuelpump speed control switches the pumps earth from direct to the chassis to earth through the resistor

The way its drawn in the diagrams is that the negative terminal of the puel pump is connected to two places - the dropping resistor and the FPCM. The resistor is hardwired between the pumps negative terminal and the earth. The FPCM switches on and off based on the ECU signal and effectively shorts out the dropping resistor.

Don't know why Nissan did it this way. I guess if the FPCM fails, then you can still run the pump at low speed so you can limp somewhere to get it fixed.

[BHDave]

The easiest way to get around the whole low/high speed issue with a big bosch pump is to run dedicated 20amp wire from the battery to the new pump and use the existing wire as a trigger for a new relay. Then run a new earth wire to the chassis (or back to the battery if you are paranoid about voltage drop).

That way, whether the ecu is outputting high or low speed, the relay is still closed so the pump is getting a constant high voltage (which the bosch pumps need anyway)

[browny]

yes, thats the way mine is set up.

[BH_SLO32]

I was under the impression the fuel pressure reg. controls fuel pressure. By increasing/decreasing the voltage across the pump, the FLOW capacity of the pump would increased/decreased.

<{POST_SNAPBACK}>

Yes, the fuel pressure regulator controls the pressure in the fuel rail relative to the manifold pressure (most factory regulators are set to maintain the fuel rail pressure at about 43kPa above the manifold pressure). Increasing the speed of the fuel pump (by increasing the current draw) increases the pressure and flow of the pump. An increase in flow is only achievable by increasing the pressure because of an increase in pipe friction and fitting losses. The friction loss increases at the rate of the square of the line velocity.

Using a large capacity pump like the Bosch O44 will naturally increase the base fuel rail pressure ( >43kPa say) if the same voltage is applied to the pump. Increasing the voltage will result in an increase in the pump speed and hence pressure and flow.

When upgrading a pump you need to consider its flow capacity at a given pressure and voltage. If the standard voltage available at the pump is deemed to be inadequate the best approach is to install a dedicated power feed to the pump to minimise voltage drop. You can then install a relay and trigger it off the old fuel pump power supply as suggested by BHDAVE.

Hope this explains things.

Edited September 5, 2005 by BH_SLO32