• Welcome to ClassicBroncos! - You are currently viewing the forums as a GUEST. To take advantage of all the site features, please take a moment to register. It's fast, simple and absolutely free. So please join our community today!
    If you have problems registering or can't log into your account, please contact Admin.

Electric fuel pump wiring

guidoverduci

Sr. Member
Joined
Mar 8, 2012
Messages
719
Loc.
NorCal
I’m currently running the carter P4070 fuel pump. I’m curious if it’s suppose to run on ACC or if it’s wired wrong. Also- any issue with these running for a bit without starting the engine? I’m working on stereo setup stuff and I need to have the power on for awhile during setup. Thanks
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
No, it should not. And yes, it's an issue (unless you have a return line and a good battery?).
More details in a moment. Just wanted to get this out there.

Paul
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
As you figured, the pump should come on in RUN/ON only, never in ACC positions. Otherwise you could never just sit there and listen to music.
Even modern cars that turn the pump on and off with the computer still don't run the pump for those first few seconds only in ACC.

Probably the pump on yours was connected to the easiest spot on the ignition switch, which is the ACC stud. Very convenient, but not suitable for every function.

Your pump should be run on a relay controlled by one of the ON-only circuits. With our ignition switches there are only two of those I believe, which are the Green w/red and Red w/green wires. The first runs the original voltage regulator, the second runs the ignition.
If you are running a modern alternator then the old Green w/red might just be waiting to serve you in it's new fuel pump function.
And I'd use that one first anyway, just to keep from using your ignition wiring for anything else.

A standard Bosch-type 4 or 5 pin relay can easily be used here.
Mount it under the hood on the fender or firewall, run the #30 pin to the battery with a fuse, #87 out to the fuel pump, #85 to a good ground near the relay, and #86 to the ignition switch's Green w/red wire at the voltage regulator.
Use 14g wire for #30 and #87, and just 18g or so for the other two. You can use 14g for it all of course, but it's overkill for the control circuits.

You really should have a fuel-pump shutoff or oil pressure shutoff switch stuck in there somewhere too though, so the pump is never running when the engine is not running.
It's a valuable safety feature.

Paul
 

73azbronco

Contributor
Bronco Guru
Joined
Nov 11, 2007
Messages
7,796
One change I would do to that wiring diagram is have the inertia switch run through the relay power from ignition, vs straight through it to the pump. That way the inertia sw only sees the current needed to activate the relay, not the pump.

In fact wiring this in this week. I hope.

BTW that pump, same one I used on my 65 Econoline 40 years ago. No difference. Same one on my current bronco build. I will be wrapping it in dynomat like material to knock the buzz down a little.
 
OP
OP
G

guidoverduci

Sr. Member
Joined
Mar 8, 2012
Messages
719
Loc.
NorCal
Ok- thanks guys. I’ll try to wrap my head around this wiring / electrical stuff. I’ll add that I’ve got an upgraded alternator, no voltage regulator, and a previously wired painless harness.
 

ObscureMachine

Seatbelt Orifice Officer
Joined
Sep 28, 2006
Messages
3,998
Loc.
World Headquarters
One change I would do to that wiring diagram is have the inertia switch run through the relay power from ignition, vs straight through it to the pump. That way the inertia sw only sees the current needed to activate the relay, not the pump.

In fact wiring this in this week. I hope.

BTW that pump, same one I used on my 65 Econoline 40 years ago. No difference. Same one on my current bronco build. I will be wrapping it in dynomat like material to knock the buzz down a little.

This. Definitely put an inertia switch in line.
 
OP
OP
G

guidoverduci

Sr. Member
Joined
Mar 8, 2012
Messages
719
Loc.
NorCal
Is the inertia switch there for shutting off power to the relay in the event of an accident?

I read through the painless manual and even though not many of the colors seem to match... I think I can figure most of it out. Only thing I need is to find a wire to use for the ign power. Everything is tied up tight and difficult to get to- is there something I can tap into for the acc ign wire? Only green/red wire I got goes to the alternator.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
Is the inertia switch there for shutting off power to the relay in the event of an accident?

Yes. It's a backup system in case an engine keeps on running after an accident where they may be a fuel system puncture of failure that causes a leak.

I read through the painless manual and even though not many of the colors seem to match... I think I can figure most of it out.

Match what? Factory Ford?
At least half of the Painless circuits are added and don't necessarily match what you may have had on a Bronco, but some might actually match more modern Ford colors. I don't know that though, so maybe we can ask Eric sometime.
But 99% of the main circuits match the Ford colors you should have had with the original harness. There are some variations, mainly for '66 trucks that had the oddball stuff, and most year's variations in the steering column, but like you said most of that is figurable outable.
The ignition switch wiring colors are not stock unfortunately. Most are "correct in the color department, but not the location. For example the original power wire was Yellow and the original ACC wire (on the back stud) was Black w/green. The Painless has a different orientation. But things should still work.
They just won't always match the factory manuals.

Only thing I need is to find a wire to use for the ign power. Everything is tied up tight and difficult to get to- is there something I can tap into for the acc ign wire? Only green/red wire I got goes to the alternator.

Not sure of your wording. You mean that you're just wanting to find a wire that works in ON only, and not ACC, for use with your pump. Correct?
That's what started this thread, so figure that's what you meant but wanted to be sure.

I'll check the instructions, but pretty sure only the Red w/green and Green w/red wires are in ON only and not ACC. But while I would not tap into the Red w/green unless I had to, I don't see a problem tapping into the Green w/red wire for your alternator regulator as long as you use a relay to actually power the pump.
You just need to make sure that the alternator still gets what it needs. No big load needed there, so it should be able to share with the pump relay.

Paul
 
OP
OP
G

guidoverduci

Sr. Member
Joined
Mar 8, 2012
Messages
719
Loc.
NorCal
Yep... you decoded my confusion. I was partly confused because I’m not sure which harness the PO used. The fuse block is not like either of the painless bronco harness manuals I have. It more resembles a generic one for GM trucks. I was just trying to decode the coloring of the wires to trace other areas of his wiring. I’m also looking to install a horn so I was trying to have a baseline of what I’ve got. But in the meantime, I’ll tap the alternator wire, use a relay, and see how it works out!
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
I'm sure we've seen pics over time(?) but we need some now too, to make sure we answer electrical questions accurately. How's about some pics of the fuse panel and it's location, as well as starter relay/battery corner of the engine compartment, and maybe anywhere else it looks confusing or different from what you've seen.

Thanks

Paul
 

ntsqd

heratic car camper
Joined
Jan 30, 2005
Messages
3,229
Loc.
Upper SoKA
For years I have used the Vega oil pressure switch in the control wiring of the fuel pump's relay. That's it just above the spring bucket:
i-x4zMJkv-L.jpg

[hijack] yeah, that steering shaft is funky. It was how the EB was delivered to me. It no longer exists.[/hijack]

Summit link for the pressure switch: https://www.summitracing.com/parts/crt-a68301
 
OP
OP
G

guidoverduci

Sr. Member
Joined
Mar 8, 2012
Messages
719
Loc.
NorCal
Thanks for the link! Here’s some pics of my current setup.. the PO installed this door next to the glove box where the fuse box hides. The ford thing opens up to a cup holder.

Battery area seems pretty standard. I do have the wire sitting on the overflow hose. It was used for the old alternator harness. Not sure if there’s a use for it now.

On the drivers side there’s a red wire with a painted white stripe, not sure it’s purpose, but I was hoping it was used for a horn. That’s my next project.

Also, on a side note, I included a pic of the new exhaust. It’s really close to my fuel pump. They added a shield to help with heat, but I’m just curious on other opinions. Thanks!
 

Attachments

  • 5738406D-0F4A-42E9-BC78-17CD27032539.jpg
    5738406D-0F4A-42E9-BC78-17CD27032539.jpg
    99 KB · Views: 93
  • 5009E617-8B2E-4B7B-8A66-9BC9D4AB2F1B.jpg
    5009E617-8B2E-4B7B-8A66-9BC9D4AB2F1B.jpg
    104.3 KB · Views: 90
  • 8AFF8599-5F2C-4E1A-97E4-C8C25DC6882D.jpg
    8AFF8599-5F2C-4E1A-97E4-C8C25DC6882D.jpg
    105.8 KB · Views: 95
  • E852F08C-01A4-475D-8E4E-88ED74A08AD5.jpg
    E852F08C-01A4-475D-8E4E-88ED74A08AD5.jpg
    83.2 KB · Views: 87
  • 6E124D6D-BC01-4B2F-913B-F5FFF067BBA6.jpg
    6E124D6D-BC01-4B2F-913B-F5FFF067BBA6.jpg
    90.4 KB · Views: 100

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
Agree!
The heat shield is a good idea, but not only is it not enough because the tubing is just too close for it to do any good, but because it's part of the exhaust system it gets almost as hot as the rest of it does right there when running. Yes, the air gap will let it cool quicker, and perhaps when you're moving a little bit of air will keep the plate a few degrees (or maybe quite a bit with any luck) cooler than the tubing, it's still radiating butt loads of heat right at the pump.

But you see the dilemma, and why so many of us have gone back to either a single exhaust on the passenger side, or duals run down the passenger side.
There's just not enough room for even the stock wiring and plumbing with normal dual exhaust.

The Carter pump is very robust and is probably doing just fine for it's light duties for now, but I can't imagine that being that close to the exhaust won't at least shorten it's life. Especially the more you drive it out on the open road on longer trips.
Maybe it's life is mostly around town and on short trips? Maybe that's what's saving it so far.

Good luck.

Paul
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
Oh, and the fuse panel is either a generic GM style out of probably an '80's vintage or so passenger car, or is a Centech panel.
If it was the Centech version (their GV-16 is a full harness with that exact panel) I'm pretty sure it would say Centech on it however.

Nice setup and someone went to some trouble to graft it in there. Looks like the stock wiring is still being used, but they removed the pesky stock panel and replaced it with this one.
If they do a good job that's not a bad way to go.

If the wiring under the hood is all stock, a White w/red wire would be the old oil-pressure sender wire.
But a Red w/white one I'd have to look up to see what else it might have been. Not the normal color for a horn from any year I don't think.

Paul
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
I’ve got header wrap lying around, think that would help?

Yes, without a doubt.
I'd still wrap it around the exhaust like it's intended. In case you got to contemplating wrapping the pump when you got back under there.

Paul
 

ntsqd

heratic car camper
Joined
Jan 30, 2005
Messages
3,229
Loc.
Upper SoKA
If you're going to wrap it, knock that short piece of tube off to buy yourself some air gap distance.

Or move the pump. Is that cross-member in front of the tank not an option? It wasn't for me, but I don't recall why.
 
Top