Fuel Pump Resistor
05-02-14, 08:54 PM
#1
Fuel Pump Resistor
Since i'll be doing the fuel pump rewire here soon and running it's own dedicated circuit, do I still need to plug in the fuel pump resistor?
I'm honestly oblivious to it's function but I like to get rid of things I don't need.
I'm honestly oblivious to it's function but I like to get rid of things I don't need.
05-03-14, 03:56 PM
#2
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Hi there,
well the role of the FP resister is to 'reduce' the voltage the pump see's (less noise/ heat/ pump life extended). Basically, the FP wiring splits to the FP relay 'speed' and the fuel pump resister. At low speed/ low load the power flow has no option but to pass through the resister circuit, thereby dropping the voltage. AT high speed the relay path is open, and power always flows through the path of least resistance; hence it goes through the relay circuit, the the FP resister.
So if you remove the FP resister, you would need to do 2 things:
1 - that the FP relay speed is 'hardwire' - it usually gets its signal from the ECU based on load. So you want to hard wire that relay so its always closed and power flowing.
or;
2 - hardwire/ run wire from the circuit opening relay (aka the fuel pump power relay, next to the EGI relay) to the fuel pump. The wire you need to splice into is a thick wire (light blue with a red tracer) and run this to the FP directly. Easy for you at present with the carpets out etc!
see page z 28
http://wright-here.net/files/manuals...20Diagrams.pdf
Now one thing I do not know is that if you bypass the ECU FP speed signal, whether this will throw and error code on the factory ECU....
All the best, Rusty
well the role of the FP resister is to 'reduce' the voltage the pump see's (less noise/ heat/ pump life extended). Basically, the FP wiring splits to the FP relay 'speed' and the fuel pump resister. At low speed/ low load the power flow has no option but to pass through the resister circuit, thereby dropping the voltage. AT high speed the relay path is open, and power always flows through the path of least resistance; hence it goes through the relay circuit, the the FP resister.
So if you remove the FP resister, you would need to do 2 things:
1 - that the FP relay speed is 'hardwire' - it usually gets its signal from the ECU based on load. So you want to hard wire that relay so its always closed and power flowing.
or;
2 - hardwire/ run wire from the circuit opening relay (aka the fuel pump power relay, next to the EGI relay) to the fuel pump. The wire you need to splice into is a thick wire (light blue with a red tracer) and run this to the FP directly. Easy for you at present with the carpets out etc!
see page z 28
http://wright-here.net/files/manuals...20Diagrams.pdf
Now one thing I do not know is that if you bypass the ECU FP speed signal, whether this will throw and error code on the factory ECU....
All the best, Rusty
05-03-14, 07:41 PM
#3
Ok, when I do the rewire as you posted, I want to make sure the car is running well before I slap my PFC in. So, when I'm running on the stock ecu, I'll be sure to plug it in and unplug it when I get the PFC in there.
Also, the write ups that I've seen just run a power wire from the battery and connect it to a relay so when the ignition is turned on, the relay energizes and sends full voltage to the fuel pump. From my understanding that's the whole point of the rewire, to ensure the fuel pump get proper voltage at any given time. It seems though, that doing this bypasses the resistor and the speed relay altogether so I see no need to keep the resistor connected.
But like you, I have no idea whether or not this would throw a code on the stock ECU. I think the only code it would throw is if the fuel pressure was low but idk.
Also, the write ups that I've seen just run a power wire from the battery and connect it to a relay so when the ignition is turned on, the relay energizes and sends full voltage to the fuel pump. From my understanding that's the whole point of the rewire, to ensure the fuel pump get proper voltage at any given time. It seems though, that doing this bypasses the resistor and the speed relay altogether so I see no need to keep the resistor connected.
But like you, I have no idea whether or not this would throw a code on the stock ECU. I think the only code it would throw is if the fuel pressure was low but idk.
05-03-14, 08:15 PM
#4
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if you remove the relay with the stock computer it will throw code 51, which is a limp home code.
additionally, my car ran noticeably richer with the resistor disconnected.
so i would rewire the fuel pump after you put the PFC in, as the PFC won't throw a code, and you can tune the light load bits
additionally, my car ran noticeably richer with the resistor disconnected.
so i would rewire the fuel pump after you put the PFC in, as the PFC won't throw a code, and you can tune the light load bits
05-03-14, 09:04 PM
#5
if you remove the relay with the stock computer it will throw code 51, which is a limp home code.
additionally, my car ran noticeably richer with the resistor disconnected.
so i would rewire the fuel pump after you put the PFC in, as the PFC won't throw a code, and you can tune the light load bits
additionally, my car ran noticeably richer with the resistor disconnected.
so i would rewire the fuel pump after you put the PFC in, as the PFC won't throw a code, and you can tune the light load bits
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