secondary fuel pump wiring
secondary fuel pump wiring hey, im wiring my second 225 fuel pump in. it goes to a hobbs switch that activates at 1psi. will it be okay if i go to the back of the alternator for the power source to the hobbs?
I keep seeing my car hit boost from vacuum so quickly I hate to think a pump in the tank will get fuel in the injectors fast enough from a Hobbs signal.
I am going with a toggle switch for my 2nd in tank pump to run if I expect to hit boost.
I've read guys running twin pumps powered full time without issue.
Almost seems like - 'why wait?' - the excess fuel will just run back the return line cooling the pumps until used under boost...
'I keep seeing my car hit boost from vacuum so quickly I hate to think a pump in the tank will get fuel in the injectors fast enough from a Hobbs signal."`
What level of HP, [boost] will the first pump cover?? UR are assuming that you are out of pump as soon as the boost comes on.... Does it? Data logs showing it go lean at the onset of boost?
If your first pump won't cover at least part of the increased HP, then the pump is suspect....
What level of HP, [boost] will the first pump cover?? UR are assuming that you are out of pump as soon as the boost comes on.... Does it? Data logs showing it go lean at the onset of boost?
If your first pump won't cover at least part of the increased HP, then the pump is suspect....
'I keep seeing my car hit boost from vacuum so quickly I hate to think a pump in the tank will get fuel in the injectors fast enough from a Hobbs signal."`
What level of HP, [boost] will the first pump cover?? UR are assuming that you are out of pump as soon as the boost comes on.... Does it? Data logs showing it go lean at the onset of boost?
If your first pump won't cover at least part of the increased HP, then the pump is suspect....
What level of HP, [boost] will the first pump cover?? UR are assuming that you are out of pump as soon as the boost comes on.... Does it? Data logs showing it go lean at the onset of boost?
If your first pump won't cover at least part of the increased HP, then the pump is suspect....
It seems the common rational s saving wear on the second pump by using it part time.
Hmmm - by using twins all the time will that equal less demand from what would be the primary pump??
The fact is that the fuel overheats not the pumps.
Every watt of power that a pump draws is turned into heat in the fuel, plus the extra circulation pushes the fuel through the rails & under the hood picking up additional heat. As the fuel gets hot, it then starts to vaporize as it is drawn into the pumps & this is where the pumps cavitate & car vaporlocks. This can either ruin the pump or at minimum strand you on the side of the road until things cool off.
This is also why pump controllers exist for big external pumps as well.
I would not use a hobbs switch in all my dual pumps if I did not feel it was a good thing to do.
Also the pump load is constant at a given pressure. The pump pushes say 255lph, no matter if it is used by the engine or returned to the tank. 2 pumps will do twice the work.
Every watt of power that a pump draws is turned into heat in the fuel, plus the extra circulation pushes the fuel through the rails & under the hood picking up additional heat. As the fuel gets hot, it then starts to vaporize as it is drawn into the pumps & this is where the pumps cavitate & car vaporlocks. This can either ruin the pump or at minimum strand you on the side of the road until things cool off.
This is also why pump controllers exist for big external pumps as well.
I would not use a hobbs switch in all my dual pumps if I did not feel it was a good thing to do.
Also the pump load is constant at a given pressure. The pump pushes say 255lph, no matter if it is used by the engine or returned to the tank. 2 pumps will do twice the work.
Last edited by Lonnies Performance; Jun 24, 2011 at 11:11 PM.
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Verdad Gallardo back up - i bought a 2psi Hobbs switch and had already got another Hotwire kit from Racetronics.
Now I see I will have extra plugs to the car utilized by primary pump, not being used by 2nd pump - PCM, pump prime etc.
I feel a relay is needed, how do I go from the alternator / Hobbs / into the relay and out with just the power wire to 2nd fuel pump?
At relay:
Hobbs power into term 86
power to 2nd pump out term 30?
Now I see I will have extra plugs to the car utilized by primary pump, not being used by 2nd pump - PCM, pump prime etc.
I feel a relay is needed, how do I go from the alternator / Hobbs / into the relay and out with just the power wire to 2nd fuel pump?
At relay:
Hobbs power into term 86
power to 2nd pump out term 30?
30 12v in red
86 12v output to pump gry
85 grd trigger blk
87 12v trigger grn
To use the kit, splice into the ground leg for the hobbs and tee the grn trigger wire to the stock PCM control wire from R9. 30 to the alt output lug and 86 to the pump
For the trigger wire, are you tapping the wire by the pcm? For the 98, it looks like B37. I have my relay for the second pump in the rear along with my battery. Is there not a switch wire back there?
