Help me understand the fuel system!

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doogievlg

doogievlg

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Ok so I recently was given an old Holley electric pump. I plan on installing it in a few weeks and just wanted to make sure I understood everything before tearing into it.

I plan on installing the pump somewhere below the tank to help feed it. I install the regulator on the outlet side of the pump then just connect it back to the fuel line, correct? Then just run the electric for a switch somewhere inside the car.

Just want to make sure I am not forgetting anything.
 
doogievlg said:
Ok so I recently was given an old Holley electric pump. I plan on installing it in a few weeks and just wanted to make sure I understood everything before tearing into it.

I plan on installing the pump somewhere below the tank to help feed it. I install the regulator on the outlet side of the pump then just connect it back to the fuel line, correct? Then just run the electric for a switch somewhere inside the car.

Just want to make sure I am not forgetting anything.
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I can't say I've ever seen the regulator right in front of the pump in the rear of the car. They are usually installed under the hood close to the carb. I suppose it should still work the same but make sure you are reading fuel pressure at the carb and not at the regulator if you put it back there. The pump can be mounted away from the fuel tank, as long as the inlet of the pump is (elevation wise) below the outlet of the tank. Not necessarily right under the tank if you get what I mean.

Oh and yes, put the pump on a switch with a relay.
 
your going to want the regulator right before the carb. that way you can see your actual fuel pressure as sell as get an accurate reading of pressure just before the carb.
 
Regulator........depends. If it's a return type you want a separate line back to the tank. Whatever you do, don't be tempted to install the pump up front. "pushing" helps eliminate boiling fuel / vapor lock in the line "coming up" front

Relay / switch. CONSIDER. Just what might happen if you wreck it? You can use something like a Ferd Ranger crash switch in series with the relay. You can ALSO hide a switch somewhere in the relay coil circuit for anti--theft. ALWAYS wire the thing to switched ignition so it "kills" with the key. Notice what the pump draws for power, bigger wire is always better than smaller LOL
 
67Dart273 said:
Relay / switch. CONSIDER. Just what might happen if you wreck it? You can use something like a Ferd Ranger crash switch in series with the relay. You can ALSO hide a switch somewhere in the relay coil circuit for anti--theft. ALWAYS wire the thing to switched ignition so it "kills" with the key. Notice what the pump draws for power, bigger wire is always better than smaller LOL
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X2! I also used a Ford Ranger crash switch and use it as an anti-theft device as well.
 
It's an impact switch that is activated when involved in an accident. Fords have had them installed in all of their fuel injected vehicles since the 80's. Cars are usually in the trunk on a side panel, or up front behind a kick panel. Do a google search for a picture and hit the boneyard. Or just stop by a ford dealer and order one.
 
It's called an inertia switch and looks like below. That red switch will get tripped in an accident, cutting off that circuit. You can also manually trip the switch for theft deterrent. I know the '98 Rangers have them. Just go grab one from the junkyard with the pigtail harness.

4a37d3b.jpg
 
if that is a holley rotor style pump, like a blue or black, and you're running a factory sender and tank pickup, you may experience issues with fuel drainback, as well as priming the system initially. as someone noted above, those pumps are pushers, not pullers. it will absolutely NOT siphon gas up and out of the pickup tube, unless you take something like a shop vac and prime the fuel through the lines to it. those pumps are designed to gravity feed, not to siphon. also the regulator needs to be near the carb, and you need to get a return style, and run a return line. if you dead head the system, you'll get a summer or 2 out of a rotor vane style pump, before it gets hot from cavitation and dies. This is all from direct experience over the last 15 years of building street and race cars. i want to save you the issues that i didn't know about back when i started putting my car together, and this is definitely something i dealt with, and experienced all the issues above.
 
johnnymac2k6 said:
if that is a holley rotor style pump, like a blue or black, and you're running a factory sender and tank pickup, you may experience issues with fuel drainback, as well as priming the system initially. as someone noted above, those pumps are pushers, not pullers. it will absolutely NOT siphon gas up and out of the pickup tube, unless you take something like a shop vac and prime the fuel through the lines to it. those pumps are designed to gravity feed, not to siphon. also the regulator needs to be near the carb, and you need to get a return style, and run a return line. if you dead head the system, you'll get a summer or 2 out of a rotor vane style pump, before it gets hot from cavitation and dies. This is all from direct experience over the last 15 years of building street and race cars. i want to save you the issues that i didn't know about back when i started putting my car together, and this is definitely something i dealt with, and experienced all the issues above.
Click to expand...

So when I run the return line what do I connect it back too?
 
You can either drill a hole in the sending unit and braze in a nipple to hook a return line to, or buy a new sending unit that already has the extra port. I think '70-up had it for emissions purposes.
 
I know you probably don't have a fuel cell but here's how the they are set up. There are 2 lines on the top. One is vent and one is a fuel return line. With a regular tank, what 69_340_GTS said is what you'll need to do.

 
Back in the 80s I ran a Cadillac PFI pump with a homemade brass T bypass regulator that returned into the filler neck. I kept line pressure to the Holley regulator up front at about 20 PSI and regulated it to 8 PSI to the carbs. It had 5/16 line and still fed a 440 Six Pack through the 1/4 mile.
 
Can also drill a hole in the top of the fuel tank and tap in a barbed fitting with some thread sealer. I myself fun a fuel cell. But I believe my stock 74 swinger sending unit had a return line barb.
 
69_340_GTS said:
You can either drill a hole in the sending unit and braze in a nipple to hook a return line to, or buy a new sending unit that already has the extra port. I think '70-up had it for emissions purposes.
Click to expand...

Long before the Inertia switches were available I used an oil pressure switch. I believe I have this one on my Valiant: http://ecatalog.smpcorp.com/STD/#/vehicles/parts/num/PS-64?type=s In any case there's a lot of options there too. I don't think that I'd bother with both, but one or the other for sure.

Put them in the trigger circuit of the relay, not in the switched power side of the relay. Works the same and there's no need to run pump power thru either switch.

Based on an estimate of the total circuit length and the blue pump's amp draw, 12 gage wire is the smallest that should be considered for the pump power wire.
 
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