Fuel Pump Direct Feed Rewire.

[Cubes]

I recently checked the voltage my fuel pumps were receiving.

Voltages were consistently around 11.2v's.

I zipped down to Jaycar and picked up....

8GA OFC Red Power Cable x 6m

8GA OFC Black Power Cable x 1m

FuseHolder x 1

5AG 30AMP Fuse x 2

60amp Horn Relay x 1 (Nice big terminals to suit the 8GA cable and its spade connectors)

Red/Black Large Eye Terminals for 8GA x 1

Yellow 5.3mm Insulated Eye Terminal x 1

Yellow Large Insulated Spades x 1

Blue 6.4mm Insulated Spades x 1

Thats about it off the top of my head.

Basically, ran the red wire from the engine bay to the boot, placed the fuse inline then ran the wire to the relay, chopped the 12v feed to the fuel pump shoved a connector on the end of it and connected it to the relay, earthed the relay so that it can earth. lol, ran the new 12v feed from the relay to the fuel pumps. Earthed the fuel pump neg directly to the chassis.

Instantly I noticed the external fuel pump sounds angry as it buzzes away. Measured voltage, 13.8v, exactly whats at the battery.

The priming also sounds much more agressive, the fuel pump is definitely louder outside the car and sounds as if its spinning much faster, inside you can hardly hear it.

The warm weather will be interestering, it usually makes loud surging vibrating noises when it gets hot in traffic. I'm hoping this will help stop that some how, hopefully it doesn't make it worse.

Edited October 21, 2005 by Cubes

[Busky2k]

Yeah the stockie wiring is pretty hopeless for aftermarket pumps which easily demand >10amps when the pressures go up. I take it you have a Bosch? The surging gurgling sounds didnt go away when I rewired mine unfortunately.

[Cubes]

The stock wiring definitely has issues coping with 2 fuel pumps, I still have the intank and the external.

Driving today, the surging gurgling sound is still there, feeling the fuel pump it makes your hand numb.

[Trust33]

Cool.I think that the earthing system i have in the car now made a huge difference in the way the battery holds it's charge.Though i havent done any tests,after i made up my new earthing system i could insdtantly see that the 3yr plus old battery can hold it's charge even after being connected to the terminals and the car being off the road and not being started for a month or so at a time cranking it over charge is like it had been run the day before.

[Bl4cK32]

thanks for the list Cubes.

I'll be off to Jaycar now to do some shopping.....wanna draw up a circuit diagram too while your at it?

[Cubes]

whoohooo..

The pump noise no longer vibrates in the car.

It is damn loud outside the car with its gurgling/surging noise once the fuel heats up, just can't be heard inside the car.

[Sydneykid]

Hi Cubes, glad to see you finally did the wiring upgrade, it's a very worthwhile investment in time and not a lot of money.

You are suffering from "excessive size pump syndrome", because the 044 flows a bit over 360 litres per hour at 13.8 volts. This means every minute 6 litres of fuel is being pumped to the engine. But if it is idling or crawling along in traffic using say 1/10 of litre per minute, 5.9 litres goes back to the tank every minute. If you have say 20 litres in the tank (bit over a 1/4 on the guage), that means the 20 litres takes a bit over 3 minutes for all of it to go to the engine and back.

While it is in the engine bay it gets heated up, then it goes around again and gets heated some more. After a 15 minute slow drive with little or no airflow, the engine bay gets up around 100 degrees and so does the fuel. I have seen fuel boil in the tank ..............

To be continued

[Cubes]

Interestering.. It does sound correct, idle it around in traffic and I hear the noise, throw some nice new cool fuel in and it goes away, or go for a long drive at a constant speed and the noise goes away.

Feeling the pump it does feel like its vibrating quite a bit, makes my hand numb holding the pump while its operating.

[bj_dove]

just on the note of the low stock voltage at the fuel pump, was this taken at idle?? i was lead to believe that some skylines (32 gts-t in particular), have a variable votage unit for the fuel pump, ie. to pump less under low loads/revs.

was told this by my local tuner, so im thinking some readings taken may be lower than when the car is say cruising or driven hard.

just a thought.....

cheers

[Cubes]

The R32's do have variable speed pump control.

As soon as you touch the accelerator the pump receives the full voltage.

However, the AP Engineering PFC bypasses the variable speed control. The PFC has the pump running at full speed all the time.

I had tested the fuel pump voltage at idle, stationary with rev's and under load on boost. Voltage hardly varied, 11.2v being the peak.

Edited October 23, 2005 by Cubes

[predator]

I have just put a GTR pump in mine.. so noisey at low speeds..ok at higher speeds. I think it may be due to me using a hose clamp to secure it to the bracket.. which in turn sends the vibration right up the bracket and into the boot.. making it a noisy mofo. The stock setup has a rubber base which i think helps that.. so I have to pull it out and wrap it in some rubber.. see what difference in makes.

Interestingly, the GTR pump wiring already has secondary wiring for grounding built in..

on my stock pump, it drew 14.1v at idle.. I will have to check what is happening with the GTR one and see if the extra grounding is a good idea.

I used to have a 910 in the old r33, and was pretty quiet.

[Cubes]

My pump being 3years old is probably not helping its noise, i can't hear it at all in the car now, only outside. But it is still noisy outside, not a bad noise, a tinny bit louder than a V8 VS fuel pump.

By grounding the pump to the chassis I picked up half a volt, use the supplied loom ground and it was half a volt lower.

[bj_dove]

The R32's do have variable speed pump control.

As soon as you touch the accelerator the pump receives the full voltage.

However, the AP Engineering PFC bypasses the variable speed control. The PFC has the pump running at full speed all the time.

I had tested the fuel pump voltage at idle, stationary with rev's and under load on boost. Voltage hardly varied, 11.2v being the peak.

<{POST_SNAPBACK}>

thanks for the info, wasnt sure on the specifics of the variable voltage.

would there be any benefit of grounding the stock pump directly to the chassis? or would this interfere somehow with the standard ecu?

cheers

[Trust33]

Yes could you just splice it straight from the existing ground by putting a ''t peice'' in the gound wire and ground it to the chassie???

Edited October 23, 2005 by Trust33

[Bl4cK32]

Unless the origional ground isnt good to begin with, hence why u are redoing the wiring....

[muaythailuke]

please cont' SK, how do you prevent this?

[MonstaS4]

I've found the one thing that makes the Bosch pumps noisy is starving them of fuel. They do not like to suck fuel out of the tank. I'm running a high flow intank pump and an 044 in my commondore with no surge tank. If the fuel level drops below 1/4 tank, the bosch gets noisy as the lift pump is not constantly immersed in fuel. Otherwise its as quiet as the factory pump.

[Sydneykid]

Hi Cubes, glad to see you finally did the wiring upgrade, it's a very worthwhile investment in time and not a lot of money.

You are suffering from "excessive size pump syndrome", because the 044 flows a bit over 360 litres per hour at 13.8 volts.  This means every minute 6 litres of fuel is being pumped to the engine.  But if it is idling or crawling along in traffic using say 1/10 of litre per minute, 5.9 litres goes back to the tank every minute.  If you have say 20 litres in the tank (bit over a 1/4 on the guage), that means the 20 litres takes a bit over 3 minutes for all of it to go to the engine and back.

While it is in the engine bay it gets heated up, then it goes around again and gets heated some more.  After a 15 minute slow drive with little or no airflow, the engine bay gets up around 100 degrees and so does the fuel.  I have seen fuel boil in the tank ..............

To be continued

<{POST_SNAPBACK}>

Sorry for the delay in completing this post, we had an engine to finish building.

To get around this problem we use one of these in the race cars;

For around $100 they are a good investment if you are regularly going to the track. Especially in summer, sitting in the que waiting for a run with a low fuel level in the tank (no sense carrying excessive weight). Note that these are not designed for high pressure (fuel injection) so I use them in between the low pressure (lift) pump and the swirl tank. On a car with no swirl tank I have seen one used on the return from the engine to the tank, so that it's not under pressure either. Never use one between the high pressure fuel pump and the engine, they will not handle the pressure.

On the road GTR's the FPCM takes care of that for you, it reduces the flow (voltage to the pump) according to engine load. On a GTST you have to make up something similar. I have done this in the past by using a Jaycar kit #KC5377 (~$30), connecting it its input to the AFM input pin on the ECU plug.

At low air flows (say up to 2.5 volts) it drops the fuel pump voltage down via a resistor, which keeps the fuel flow slow. Once the airflow gets over 2.5 volts the fuel pump gets its full dose of 13.8 volts. I have also seen this sytem used when you have 2 fuel pumps and only one is needed at low engine load, the second pump kicks in when necessary at higher engine loads.

This is the circuit (courtesy of Performance Electronics for Cars, get one from Jaycar, for $20 its worth having one as a reference);

Note that the kit only has a 5 amp relay on the board, so you need to use a larger (30 amp minimum) relay in the circuit for the larger aftermarket fuel pumps.

Hope that helps

cheers

Edited October 24, 2005 by Sydneykid

[SimonR32]

ok i did this today so this may help ppl install a bit easier (note this is for a r32 gts-t, not sure if wires are the same as other models)

on a 30amp horn relay (all that is needed for a single pump)

first you need to find the white/pruple wire on the pump side of the clip and cut in half. the blue/yellow wire is also cut and earthed

#30 is a direct power feed from the battery with a fuse

#87 is to the pump side of the cut white/purple wire

#87a is attached to nothing

#85 is earthed

#86 is attached to non-pump side white/purple wire

[Tangles]

Im getting my workshop to do it to my Stagea (with high pressure fuel lines & bosch 040 installed, plus a Nismo fuel pressure regulator) - I just dont trust myself when it comes to vehicle electronics........