I\'m looking to run new wires to the fuel pump to keep high current going to it as they apparantly lose power with the stock wiring, on the FD the relay is at the front of the engine bay, my battery is in the stock location,
just wondered how people had gone about re wiring the pump
Dale clark over on the yank site has http://www.clubrx.org/default.asp?id=5&ACT=5&content=71&mnu=5
thanks for that Robbie, i have had a read but i dont understand how it makes a difference, i thought that the main power for the pump *red and white wire) runs from the relay at the front is the cause of the problem.
can anyone shed any olight on this?
there is a rewire thread for the FC as well - seems the stock wiring is not very thick and couple with the length of the run, it can lead to a drop in voltage at the pump - instead of seeing 13V or more, the pump might only see 11V. On the FC there is a Resistor switched in series with the pump at idle and lo load, so the voltage measurement must be made when starting or driving under some load - I\'m not sure if the FD has the same circuit in it ?
there is a thread on rx7club.com...as i understand it u take a feed directly from the live in the fuse box which cuts out all the power sapping bits in the middle ..seems quite straight forward in the write up
I think the link that robbie put up is the one that you mean, he doesnt go from the fuse box, he just puts a live to the circuit relay, i thought i had to do something like you say, and run a new 12v from the fuse box.
still confused...........
yeah, the FD is the same, the fuel pump relay drops the voltage to about 6.5V at low revs for some reason. RE:Worx rewired mine with a new relay as they couldn\'t get good pressure out of my wiring even on the Supra pump.
Put it this way, after rewiring it, the new pump blew the fuel pump fuse which someone had replaced with a 10A by mistake (should be 20A)...which means that the stock pump on the stock wiring was not pulling the expected current so god knows what fuel pressure it was supplying...
The wiring from the relay to the pump isn\'t the problem. It\'s the feed to the relay that has the current drop (it goes via the ignition iirc). I put in a new supply line to the standard fuel pump relay which upped the voltage at the pump by nearly 2 volts.
Quote from: efinisteThe wiring from the relay to the pump isn\'t the problem. It\'s the feed to the relay that has the current drop (it goes via the ignition iirc). I put in a new supply line to the standard fuel pump relay which upped the voltage at the pump by nearly 2 volts.
where did you wire this to and from ? that sounds like the way it was done in the link above to the rx7 club
I\'ll take a look tonight but from memory there\'s a good feed, straight from the battery, nearby. Use that to replace the standard feed on the relay. I can\'t remember colours off the top of my head but that link above is pretty much spot on. You\'ll find that there\'s a big supply in that fuse box that you can use (two thick wires running to a metal plate that feeds the other relays in there), rather than running another wire to the battery.
Just read through that link and the pics have jogged my memory a bit. In that fuse box there\'s an empty fuse holder that receives a feed direct from the battery (via the thick wires mentioned in my last post). Use that to supply the fuel pump relay. It\'s pretty straightforward once you\'re actually looking at it. You just remove the 20a fuse from under the dash and put it into the spare holder you\'ve just used.
so to clarify, this is the circuit relay not the fuel pump relay on the slam panel at the front of the car. Do i leave that one stock then?, i had a look and the wires seem quite thick going to the fuel pump relay.
do you have to do this mod if your injector duty is up to mark at high boost showing on pfc commander?? I did rewire the pump on my black car as shown in that link but then had to change the fuel lines on top of the engine as they couldn\'t keep up with the fuel pressure and burst on idle. I think that mod is done on standard fuel pump.
I think the mod should be done to all cars regardless of pump as a bigger pump needs even more juice. All the pumps are designed to run at their optimum at around 13v, anything less and its not running efficiently.
Your lines bursting is a different issue, this is too much fuel pressure which is controlled by your FPR, no matter how big you pump, with a good FPR you can run low fuel pressure, if the FPR is too small or their is a restriction in the line then your fuel pressure will go up.
If they burst after you did the conversion you just needed to wind the pressure back down to what it was before the mod, but it just goes to show you that the conversion works and the pump works better when done.
So did you do what is show in the RX7 club link above?
Quote from: antnicukso to clarify, this is the circuit relay not the fuel pump relay on the slam panel at the front of the car. Do i leave that one stock then?, i had a look and the wires seem quite thick going to the fuel pump relay.
Yep, I\'ve not touched the one on the slam panel.
Although the wires going to the Circuit Relay look pretty substantial, the actual wiring path is very convoluted and passes through the ignition wiring and a crummy circuit box before reaching the thick wire that goes into the circuit relay. The wiring mod cuts all of that out.
sounds good, i\'ll follow the RX7 club mod then.
thanks
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
QuoteI 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
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
Sounds like a worthwhile mod any further info or pics would be great!
I will get info posted up tommorow:burnout
Saw this kit on RHD by SARD:
https://www.rhdjapan.com/home/products/product_detail.php?int_product_id=2841# (https://www.rhdjapan.com/home/products/product_detail.php?int_product_id=2841#)
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! :(
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!
surely when your pump "dies" your engine does also??
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.
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
thank you chris very informative post :D
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)
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
The way I will be wiring my fuel pump is to use a new relay (not 13 yr old), energise its coil from the ignition switch (ign on). Then use a nice thick cable direct from the battery (inline fuse) via the relay contacts straight to the pump. Doing it this way will eliminate all the old loom connections, resistor, extra relay contacts etc.
i did it that way on my fc, only prob is that he fuel pump is pumping when the ignition is on, so if you stall or have a problem, the pump still pumps, ie in an accident where the car would stall the pump would normally stop but wiring like you say it wont.
Only a slim chance of being a problem but that maybe what caused blitzboys car to go up.
Quote from: antnicuki did it that way on my fc, only prob is that he fuel pump is pumping when the ignition is on, so if you stall or have a problem, the pump still pumps, ie in an accident where the car would stall the pump would normally stop but wiring like you say it wont.
Only a slim chance of being a problem but that maybe what caused blitzboys car to go up.
Absolutely right, it is very advisable to keep the original relay switching circuit, as you say this gives you the safety cut features if the worst were to happen.
If you do choose to replace the relay I would advise using something fairly hefty with 9mm contacts rather than the standard 6.3mm then retain the Black and light green (B/LG) relay coil supply and Blue and Red (L/R) relay coil switch wire (controlled by the ecu)
Is the safety cut a feature of the ecu and do you know when it activates?
If it is ecu controlled you could use the method above but use the ecu feed to energise the relay coil and keep everything else the same.
Quote from: SpartacusIs the safety cut a feature of the ecu and do you know when it activates?
If it is ecu controlled you could use the method above but use the ecu feed to energise the relay coil and keep everything else the same.
The ecu will initially switch this relay on for a couple of seconds to \'charge\' the fuel rail, when the ignition is switched on, it then switches again (from memory) when it recieves a cranking signal from the crank angle sensors, if you plough into a wall, there is a good chance the engine will stop, hence the fuel supply stopping (on some cars there is an impact switch which pops up in the case of impact to stop the fuel pump (mazda do not have this function)
If you are looking to replace the relay I would recommend something like this
http://www.vehicle-wiring-products.eu/VWP-onlinestore/relays/relays.php#high
(R70 and R70N are more than capable) They also sell maxi fuses, wire, crimps etc etc
Thanks for that, following a bit of a search I’ve found out that the LS1 ecu has the same function in that it supplies a signal for a couple of seconds but if it doesn’t see the engine start during that time the signal is cut.
So rather than using the Ign on I\'ll use the feed from the ecu to energise the relay coil and use a fused supply direct from the battery to power the fuel pump.
i think the other reason you cant just use the existing power wires to switch a new relay with new power wires is because they only see 6 volts at times and its not enough to open the new relay
From the look of the circuit diagram you could either jumper the existing relay at the front, or jumper the resister (with a suitable cable) and have a constant battery voltage rather than the lower voltage. Obviously doing this alone would still leave you with the problem of the potential loss through the existing cables and connectors, but you could do it just to supply the trigger for a new relay. Personally I\'d go straight to the ecu trigger to energise a new relay and run a new cable to the pump so you loose all the old relay contacts, joints and cable.
The down side of jumping the relay is that you still retain any additional alarm cuts that may be further down the line from the ignition switch.