Discussion
Duke Thrust said:
Chaps, I've used the search function but not come up with definite information on the fuel pump mod (quite possibly my poor searching).
From what I understand the mod uses the existing fuel pump feed to power a relay on a much heftier feed to the pump?
That's correct, the new fused power feed to the pump comes from the feed to the starter motor.From what I understand the mod uses the existing fuel pump feed to power a relay on a much heftier feed to the pump?
MrCredit said:
Duke Thrust said:
Chaps, I've used the search function but not come up with definite information on the fuel pump mod (quite possibly my poor searching).
From what I understand the mod uses the existing fuel pump feed to power a relay on a much heftier feed to the pump?
That's correct, the new fused power feed to the pump comes from the feed to the starter motor.From what I understand the mod uses the existing fuel pump feed to power a relay on a much heftier feed to the pump?
Looks like a nice easy job then - need to get an in-line fuse holder. Did you put the fuse before or after the relay?
[/pic]jimbooo said:
ok dumb question of the day... whats the benefit of the mod. is it a case of if it isnt broken dont fix it or not?
As far as i know, the standard wires used are so small (about the size of phone cable) that the pump can struggle to keep up under full throttle, so the pump can cut out. Replacing the wires gives a better power supply to the pump. I had bad problems with mine, done the mod, now it's running fine! 
Metalman said:
jimbooo said:
ok dumb question of the day... whats the benefit of the mod. is it a case of if it isnt broken dont fix it or not?
As far as i know, the standard wires used are so small (about the size of phone cable) that the pump can struggle to keep up under full throttle, so the pump can cut out. Replacing the wires gives a better power supply to the pump. I had bad problems with mine, done the mod, now it's running fine!
so could that be why on occasion my car cuts out for a second when i floor it in 3rd to overtake?
its like ive hit a brick wall for a second, release throttle then on again then it fires up instantly and im off again at full power. it only happens every now and then and always when petrol tank is half empty, never when full. that could be coinsidence though.
jimbooo said:
Metalman said:
jimbooo said:
ok dumb question of the day... whats the benefit of the mod. is it a case of if it isnt broken dont fix it or not?
As far as i know, the standard wires used are so small (about the size of phone cable) that the pump can struggle to keep up under full throttle, so the pump can cut out. Replacing the wires gives a better power supply to the pump. I had bad problems with mine, done the mod, now it's running fine! its like ive hit a brick wall for a second, release throttle then on again then it fires up instantly and im off again at full power. it only happens every now and then and always when petrol tank is half empty, never when full. that could be coinsidence though.
t and kinked when the fuel got warm, so i replaced it with a good quality hose and put a nice gradual bend in it. I also replaced the old paper filter for the metal full flow filter.jimbooo said:
ok dumb question of the day... whats the benefit of the mod. is it a case of if it isnt broken dont fix it or not?
Problem is that the stock fuel pump wiring is woefully undersized. On one of the M400s around here (with stock wiring), I hooked up a voltmeter across the fuel pump. I expected to see at least 13 volts at the fuel pump at idle, dropping to around 11 volts under load. What I actually saw was around 10-11 volts at idle, dropping to 7-9 volts when I blipped the throttle. Which means that the fuel pump wasn't getting enough juice to maintain its flow - this explained why the engine would go lean under load on our dyno. Once I performed the wiring mod, the leanness disappeared, and the voltages stayed at the expected levels.
Cheers Simon, I'll get that sorted this weekendMrCredit said:
TuxMan said:
No worries mate , if you get any issues give me a shout , don,t forget to crimp and solder all joints !! only thing i would have liked to get was a relay with a rubber boot to keep the weather off it !!
Put it in a condom!! 
..................not a bad idea !!MrCredit said:
TuxMan said:
No worries mate , if you get any issues give me a shout , don,t forget to crimp and solder all joints !! only thing i would have liked to get was a relay with a rubber boot to keep the weather off it !!
Put it in a condom!! h to sort. Whatever you do don't just cut it off as it only has three wires. Nightmareworty
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