• 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.

Relay to an electric fuel pump

Bundy

Bronco Guru
Joined
Jan 10, 2009
Messages
2,045
How much of a necessity is it to use a relay on the carter low pressure fuel pumps?

I have duel pumps (one per tank) and have them wired without the relay... wondering if it will give me problems although I don't think they were wired before with a relay.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
I've never ran one. The carter pumps only draw about 5 amps so I dont see a need for a relay it just makes for exrta wires.
 

diveman

New Member
Joined
Aug 29, 2010
Messages
24
Loc.
Branson, MO
i use a relay so its not wired directly to the ignition and i dont have to use a switch.(although i do have a switch wired just in case)
 

73stallion

Bronco Guru
Joined
Mar 5, 2004
Messages
16,786
Loc.
Eugene, OR
don't have one on my P4070 and i'm running directly off the terminal on the back of my ignition switch no problem.
 

Steve83

Bronco Guru
Joined
Jul 16, 2003
Messages
8,981
Loc.
Memphis, TN, USA, Earth, Milky Way
A relay isn't a requirement, but an inertia switch is. You need something to kill the pumps if you have a wreck. If you have the pumps wired directly to the ig.sw., and you wreck badly enough to rupture the fuel lines anywhere near the engine, exhaust, or wiring, an electric pump can dump the gas tank and roast you if you're unable (or forget) to turn the key off instantly. They're easy to find in junkyards, and easy to wire into the pump power circuit, so don't take a chance.

.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Wreck badly enough and it probably wont matter I got several interia switches none installed yet( probably never will) and I've been running a carter pump for over 30 years. the trick is dont get in a wreck. What better way but to go down in flames with your bronco? Aside from that a interia switch is a good idea.
 
OP
OP
Bundy

Bundy

Bronco Guru
Joined
Jan 10, 2009
Messages
2,045
How does the inertia switch work? Does the switch take the physical impact and that is what trips it? I am just wondering because i would be more likely to install one if they worked in a rollover (WAY more likely)
 

Steve83

Bronco Guru
Joined
Jul 16, 2003
Messages
8,981
Loc.
Memphis, TN, USA, Earth, Milky Way
Did you look at those pics I posted? If you can't see them, go to your settings and turn on images in posts & signatures. There are more showing details of the inertia switches - just click PREV/NEXT in the new window.

Yes, the switch is much easier to trip when it's upside-down.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Yes they work upon impact and sometimes it takes a lot and sometimes it takes very little for them to kickout.
 

NYLES

Bronco Guru
Joined
Aug 13, 2004
Messages
9,846
I use a oil pressure cut-off switch, oil pressure drops below 15psi... kills it. Got it at Napa and you can get them in diff psi levels. My oil pressure stays around 50 psi running so 15 is ok with me.

Used heater fused circut no relay. BTW I dont have a heater never will so made good use of the wires.
 

jw0747

Contributor
Bronco Guru
Joined
Nov 22, 2006
Messages
2,434
Loc.
San Antonio, TX
if you plan to do any hard crawling or driving on rugged terrain inertia switches are junk.
as stated earlier, they tend to trip when you don't want them to. then you spend lots of time on the side of the trail trying to figure out what happened that caused the whole deal to go dead. I use a toggle switch that is within easy reach. It worked beautifully when I turned over 3 ys ago.
 

Steve83

Bronco Guru
Joined
Jul 16, 2003
Messages
8,981
Loc.
Memphis, TN, USA, Earth, Milky Way
I've off-roaded my truck hard enough to bend the body, crush the fenders, and split rocks with the front bumper, and my (junkyard) inertia switch has never tripped. But when I rolled the truck on the interstate, it shut off the fuel pump. So if yours didn't work right, it was probably just worn out, but that doesn't make it a bad idea. And the later style has an extra terminal so you can wire up a light to tell you when it's tripped.
 
Top