Have you Rewired your Fuel Pump ?

[antnicuk]

sounds good,  i\'ll follow the RX7 club mod then.

thanks

[chris]

Hi Tony,

The club rx mod is an easy one, but does not eliminate all the excess wiring
( I am unable to attach a drawing…..)
The standard fuel pump wiring allows the pump to run at reduced voltage under low load operation (through the finned resistor located under your brake master cylinder), then steps up to full voltage (or as near as possible) under load.

The circuit is such that the power comes from the main fusebox, into the ignition switch, when you turn the ignition on, the supply is then on to the circuit opening relay.
 NOTE: This is the main power that alarm fitters usually cut (there are many posts/discussions about this very wire on the forum) basically cutting this nice thick wire and putting a tiny alarm circuit in the mix is not a great move!

When the ECU receives cranking signal, it switches this relay on, you then send the supply right round the front of the car to the fuel pump resistor, then back round the front to the passenger foot well and back to the fuel pump, this supplies approx 6volts from memory to the pump.

When increased load is detected the ECU then switches on the fuel pump relay (located in the relay box by the nosecone) this bypasses the resistor and supplies battery voltage back to the passenger foot well, and finally the pump.

So as most of these cars are well over 10 years old, with various alarms/immobilisers and old switches, contacts, relays and wiring, a refresh/rewire of this circuit is a great idea.

I can write up the way I have rewired my fuel system if this helps

[ro284]

I can write up the way I have rewired my fuel system if this helps

Be great if you would thanks Chris, been hoping to find time to do mine, (with a concealed anti theft switch in the cabin somewhere!)
Cheers Bob

[antnicuk]

Hi Cris
very helpfull,  if you cant post it, email it to me at antnicuk@msn.com and if you wish i will post it

regards
Tony

[Initial-D]

Sounds like a worthwhile mod any further info or pics would be great!

[chris]

I will get info posted up tommorow:burnout

[gmogle]

Saw this kit on RHD by SARD:
https://www.rhdjapan.com/home/products/product_detail.php?int_product_id=2841#

[m4drx]

i dont get it

you run a wire directly from your positive battery terminal to the wire going out of the relay box and eliminate the old relay in the process??

or to the fuel pump?

where does the red wire go?

good mod that i want to do tho. But i cant get my fuel pump cover off to check the voltage!

[ashc]

i did read somewhere whilst researching this that mazda did it deliberately to preserve the life of the pump, and that running at max can significantly reduce its life. But we don\'t care about that if we want more juice!

[m4drx]

surely when your pump "dies" your engine does also??

[TonyC]

Biggest probem is that if the pump dies the engine is fuel starved. Sods law says the pump will die under stress (pumping lots at high revs), and lean mix with high revs seems to mean pop with these rotary motorys.

Mine\'s all wired seperatly - but then again most of the original loom is in a bag on the garage floor. I\'ve a live junction box behind the dash where all my live feeds route from once they\'ve been through the battery master cut off switch., I\'ve router seperate switches on the dash -one to the original pump that primes and feeds the swirl pot, then the second switch runs the Bosch pump that drains the swirl pot and feeds the injectors. All this runs through a seperate fuse box within the car (side of the transmission tunnel). ECU has no control over my pumps.

[chris]

I have mailed 3 diagrams For Tony to post, these should help this explanation

This is friendly guidance, all modifications are at YOUR risk

There are two options regarding wiring for the fuel pump, one retaining the fuel pump resistor, the second ditching it.

Firstly looking at the main diagram that Tony will hopefully post up, you will see a section at the top highlighted blue, this is the main power from the battery, through the main fuses to the ignition switch, through the switch, then to the fuel pump fuse, this is the section that you are likely to have an alarm cut in. (Call this section ‘A’)

From there the power goes to the circuit opening relay (highlighted pink), this is then switched on by the ECU when cranking signal has begun. This then as stated previously goes through the resistor(highlighted green), dropping voltage to around 6 volts, then onto the pump.

When load is detected the ecu switches the FUEL PUMP RELAY ‘on’ this bypasses the resistor and gives full battery voltage to the pump.

The reason for the resistor as I understand is to reduce noise and reduce the working pressure that the pump has to withstand during low demand conditions.

I have also heard of problems with fuel lines and pressure reg/pulsation dampers with continuous voltage at low demand on standard fuel systems, so where you are running stock fuel system, I would recommend only removing section ‘A’ (leaving the resistor circuit in tact)

FUSES
I would recommend using either the existing large main OEM fuses and tapping into the fused side (small blade fuses are not very good for high demand circuits/uprated pumps) You can buy larger blade fuses called ‘maxi fuses’ these are rated to supply higher demand applications, either that or a car stereo type gold fuse, fuse rating should be no more than 30 or 40Amps.

WIRE
Minimum 2mm sq, up to about 4.5mm sq

GETTING STARTED (retaining resistor)
The circuit opening relay fitted to the car is far better quality that the halfrouds blade type that you can buy so I advise retaining it.
Taking a fused supply from the battery, carry out the modification as shown in the  link from Robbie http://www.clubrx.org/default.asp?id...ntent=71&mnu=5
(Cutting the Blue wire to the relay and joining your nice new meaty fused wire from the fuse box.)
This eliminates the ‘section A’


Additional work if you wish to remove the resistor circuit
For the more adventurous with modified fuel pumps, regulators etc, at the same relay now cut the Blue with red stripe wire carefully join a long length of new wire(again min 2mm sq) from there, then feed all the way through the car to the fuel pump connector at the left hand side, under the boot carpet, cut the white with red stripe wire and connect your new wire directly to the fuel pump cut end, insulate and clip all loose wiring, refit trim etc,  job done!

(if your Air fuel ratios become rich following this mod, there is a good chance you need to uprate your pressure reg)

Good Luck

Chris:3gears-lh

[m4drx]

thank you chris very informative post

[antnicuk]

cheers chris,  makes perfect sense.   I\'m just waiting for the wife to forward me the emails and i will post them up, (i cant access MSN from work)

[antnicuk]

These are the diagrams Chris sent me,  they may be a little small so you may want to save them and enlarge them, i cant do it at work.


there are 3 diagrams but 2 are too big for me to attach and i cant reduce them or photobucket them from work so i will do it tonight