Electric Fuel Pump Wiring

[matt63]

I was wondering what the best routing is for the wiring back to the pump.  Is it best to run it underneath or inside along the doorsill?  What kind/size of wiring is best if you run it underneath? I will install a relay under the dash somewhere, perhaps on the heater box or near the fuse box.  I've also got a new low oil pressure switch that will be in the relay circuit.

[GoodysGotaCuda]

I was wondering what the best routing is for the wiring back to the pump.  Is it best to run it underneath or inside along the doorsill?  What kind/size of wiring is best if you run it underneath? I will install a relay under the dash somewhere, perhaps on the heater box or near the fuse box.  I've also got a new low oil pressure switch that will be in the relay circuit.

You might want to put a momentary toggle switch so that your not cranking forever to get enough oil psi to trigger the switch. I would run 10gauge myself, i rather have too big than too small, and definately wire it off a relay. I would recommends it through the interior, along the door sill and such. Of course properly connected/spliced, grommets through metal, etc, etc. Also stick like a 10amp fuse in there just in case. 

[Chryco Psycho]

inside is better with grommets 12 ga should be lots , relays are a good idea
 I would hook the low oil pressure switch to the ign power  not the fuel pump , a car can run a minute or so on the fuel in the Holley bowls

[matt63]

Thanks guys.  It sounds like there is a couple of options here at least. 1) wire the low oil pressure switch into the fuel pump relay and then put a  momentary toggle switch in parallel with the oil pressure switch to bypass it for start-up (I think??) 2) wire the oil pressure switch into the ignition power circuit so that the engine quits if the oil pressure drops below 15 psi.  Which ignition wires and will this prevent starting until oil pressure is attained? Won't the fuel pump keep running when the key is in the run position regardless? 3) do both- wire the oil pressure switch into the ignition circuit and the fuel pump circuit and put a parallel momentary switch in the pump relay circuit.  Yikes!

[Chryco Psycho]

it depends if the pressure switch is normally open or closed , , you need to bypass it so the car will start with the oil hot as well & yes you can wire the fuel pump into it as well to kill it when the engine is off , I though you were usding it for protection in case the engine lost oil pressure for some reason

[ShelbyDogg]

Holley sells a fuel pump safety switch. It has 3 leads and screws into the oil line like a sending unit. One side hooks to the start circuit, one to the run circuit and one to the pump.  That way you have pump voltage while cranking and when the oil pressure closes the N.O. side, the run circuit takes over. Check summitracing for the switch. All race cars use this switch if the builder knew anything about safety.

[matt63]

Thanks guys.

[matt63]

I got the pump installed a few weeks back.  So far I have just wired it through a relay and toggle switch until I get time to wire it into the oil pressure switch. 

One thing I have noticed is that the idle fuel pressure ranges from 3 at times to 7 psi.  At first I thought it didn't like the low fuel level in the tank.  I filled it up and it does the same thing.  I have attached a pic showing the mounting.  The inlet to the pump is very low but the inlet to the filter is much higher as they are on the top of the filter.  I though that the fuel would just siphon through the filter but now I wonder if I should lower the filter.  I'm just trying to keep the thing from dragging on the ground!

ps I am told that the blue fuel hose is IHRA legal.  I'll find out when I get to the track.

[matt63]

Here are the pics.

[Chryco Psycho]

I have used blue & black fuel hose with internal steel braid , it is legal