Fuel Pump Wiring
Thread Starter
Racer
Joined: Mar 2005
Posts: 473
Likes: 2
From: Champlin Minnesota
Fuel Pump Wiring
One of the last things I have to do before I fire it up, I need to route a wire from driver side wheel well where I have a fuel pump relay, all the way to the back to fuel pump which is mounted on the rear crossmember by the gas tank. Am I ok to run this wire right along with the fuel lines, or would that be a horribly bad idea. I could also run it in the interior, but only if I have to since it would require more work and I really want to drive and tune this weekend.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by davidm_comp
One of the last things I have to do before I fire it up, I need to route a wire from driver side wheel well where I have a fuel pump relay, all the way to the back to fuel pump which is mounted on the rear crossmember by the gas tank. Am I ok to run this wire right along with the fuel lines, or would that be a horribly bad idea. I could also run it in the interior, but only if I have to since it would require more work and I really want to drive and tune this weekend.
Follow the same rail as the fuel line. I was able to run my wire to the back inside that frame rail, and then up from there. The only things you really want to make sure of is that it's protected, and won't get caught on anything or struck and split by anything. So long as it's safe, and in the event of a leak, the wire never comes near the fuel...you can route it any way you like.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I too have run a few wires through the grommit in the back, where the radio antenna wire goes through, and it took about five minutes per wire. Now, I did not have ANY interior in the car, so it was as easy as laying it down, and pushing it through.
Pro
Joined: Nov 2000
Posts: 594
Likes: 0
From: Tucson AZ
Here is how I routed mine. I used 12awg GXL wire inclosed in a 1/2" non-slit loom. The tie wraps are a temp measure to hold it till I install clamps. Under the car it runs along the supply and return lines.
Please excuse all the dirt as I am in the process of sanding and making a big mess
Craig
Please excuse all the dirt as I am in the process of sanding and making a big mess
Craig
Race Director
Joined: Nov 1999
Posts: 10,643
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From: Foxfield CO 1970 Convertible
I ran my wire along the fuel line also. Link
One comment however:
The purpose of using a relay is to allow high current to flow in a device while controlling it with a low current switch (on the low current side of the relay). So that the high current device gets the highest current possible, you should locate the relay as close to the high powered device as possible. This reduces the current drop which occurs in a long length of wire. I'd relocate the relay to an area right next to your fuel pump to make sure it gets full power. Run the low current wire from the relay up to your engine compartment. This is also cheaper, since the most expensive wire is the shortest and your battery is already back there too...
One comment however:
The purpose of using a relay is to allow high current to flow in a device while controlling it with a low current switch (on the low current side of the relay). So that the high current device gets the highest current possible, you should locate the relay as close to the high powered device as possible. This reduces the current drop which occurs in a long length of wire. I'd relocate the relay to an area right next to your fuel pump to make sure it gets full power. Run the low current wire from the relay up to your engine compartment. This is also cheaper, since the most expensive wire is the shortest and your battery is already back there too...
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Thread Starter
Racer
Joined: Mar 2005
Posts: 473
Likes: 2
From: Champlin Minnesota
Thanks for the help guys. I think I will run it alongside the fuel lines. Where did you get the non-slit loom at? I will wire the fuel pump relay to a oil pressure switch and then back to a toggle switch in the cab, so in the event of a crash the pump should shut off, or I will manually if I am still alive/conscious.
Pro
Joined: Nov 2000
Posts: 594
Likes: 0
From: Tucson AZ
Originally Posted by Z-man
I ran my wire along the fuel line also. Link
One comment however:
The purpose of using a relay is to allow high current to flow in a device while controlling it with a low current switch (on the low current side of the relay). So that the high current device gets the highest current possible, you should locate the relay as close to the high powered device as possible. This reduces the current drop which occurs in a long length of wire. I'd relocate the relay to an area right next to your fuel pump to make sure it gets full power. Run the low current wire from the relay up to your engine compartment. This is also cheaper, since the most expensive wire is the shortest and your battery is already back there too...
One comment however:
The purpose of using a relay is to allow high current to flow in a device while controlling it with a low current switch (on the low current side of the relay). So that the high current device gets the highest current possible, you should locate the relay as close to the high powered device as possible. This reduces the current drop which occurs in a long length of wire. I'd relocate the relay to an area right next to your fuel pump to make sure it gets full power. Run the low current wire from the relay up to your engine compartment. This is also cheaper, since the most expensive wire is the shortest and your battery is already back there too...
Gave this advice to someone awhile back about installing headlight relays. In my case, I'm not really worried about a .25volt drop to a 110psi pump so I left my relay where it was in the injection harness. The controller also takes care of shutting off the pump when the engine stalls.
Craig
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
The Bubba that did my Vette in before moving on to one of yours, had installed the elctric pump on the signal circuit. No, he didn't do it at the fuse panel, he did it under the steering column, and did a blind tap into a wire he found to only be on with the ignition. I found this wire was the 12V ign to the signals. I have since run my own wire, but I can't imagine it worked as well as it did with no relays, manual switches, or even a full 12V with ign. Odd how it worked so well...
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by Artsvette73
It's a good idea to run the pump through an oil pressure switch. Thus the pump will only run when the engine is running. A huge safety issue
Very good point!
The equivalent of todays inertia switch.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I like the oil pressure switch, but one of the things I like being able to do is turn the key to give power to the pump. I let it pressurize the lines and fill the carb, so that when I turn the key, it rotates maybe twice before catching. With the bowls primed it starts right up every time.
Melting Slicks
Joined: Sep 2003
Posts: 3,050
Likes: 2
From: Orange Ct
Originally Posted by Durango_boy
I like the oil pressure switch, but one of the things I like being able to do is turn the key to give power to the pump. I let it pressurize the lines and fill the carb, so that when I turn the key, it rotates maybe twice before catching. With the bowls primed it starts right up every time.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Once I tested the electric on an old 360 in my pickup before I ripped it out to make way for a new motor. What I did was turn off the fuel pumps cutoff switch while the engine was running. It ran for ALMOST a minute before it died of fuel starvation.
If I had an engine problem, and suddenly lost oil pressure...if it took me a minute to even notice and shut down then I wouldn't be paying attention. Gauges are there for this reason, as well as feel and sound of the car.
Like I said, I like the oil pressure switch...I just wish there were a way to do both. Maybe a primer bypass circuit of some kind.
If I had an engine problem, and suddenly lost oil pressure...if it took me a minute to even notice and shut down then I wouldn't be paying attention. Gauges are there for this reason, as well as feel and sound of the car.
Like I said, I like the oil pressure switch...I just wish there were a way to do both. Maybe a primer bypass circuit of some kind.
