fuel pump question
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Freshman User
Joined: Aug 2006
Posts: 39
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fuel pump question
Have an 87 f150 302cid that I did a carb conversion on. I'm trying to use the low pressure fuel pump in the tank to feed the carb but the thing isn't pumping at all. I have the high pressure one simply unplugged and a direct fuel line from my rear tank to the carb.
I guess my question would be what all needs to be plugged in as far as computer controls in order for the pump to know the engine is on and to start pumping? Does the high pressure pump circuit have to be jumped? Does something else have to be tricked? Do I just run a 12v fused lead to to the pump and connect it to a switch?
Btw: It's a 600 holley, with a date correct coil and a dual point distributor... I've got spark, I tapped into the existing distributor harness and found what I need... Just need fuel.
Any ideas?
I guess my question would be what all needs to be plugged in as far as computer controls in order for the pump to know the engine is on and to start pumping? Does the high pressure pump circuit have to be jumped? Does something else have to be tricked? Do I just run a 12v fused lead to to the pump and connect it to a switch?
Btw: It's a 600 holley, with a date correct coil and a dual point distributor... I've got spark, I tapped into the existing distributor harness and found what I need... Just need fuel.
Any ideas?
Postmaster
Joined: Oct 2003
Posts: 4,516
Likes: 1
From: SoCal
When you turn the key the main relay closes & sends 12 volts thru the pump relay. The PCM grounds that voltage which closes the pump relay which connects power to the fuel pump. Very simple circuit.
To hold the pump relay closed while you check voltage see this link. First place to check for voltage is at the inertia switch under the dash.
If you did'nt mess with the splice that connects the pumps, you should be OK on the wiring.
http://www.superhighoutput.com/tech_view.php?id=5
To hold the pump relay closed while you check voltage see this link. First place to check for voltage is at the inertia switch under the dash.
If you did'nt mess with the splice that connects the pumps, you should be OK on the wiring.
http://www.superhighoutput.com/tech_view.php?id=5
Fleet Owner
Joined: Aug 2005
Posts: 23,668
Likes: 301
From: Easton,Ks
The computer will not keep the fuel pump relay giving power without PIP information from the distributor. And that you do not have.
So yes a run a hot wire to a fuse, to a switch and then to the inertia switch under the dash.
So yes a run a hot wire to a fuse, to a switch and then to the inertia switch under the dash.
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
You could run the fused power feed from the distribution post through a relay, then use an oil pressure switch on the relay control ground and a switched +12V on the relay control positive so that the pump only runs with the key in the on/run position and the engine running.
