Upgrading wiring for fuel pump?

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DRod
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Upgrading wiring for fuel pump?

Post by DRod » Mon Nov 05, 2018 1:24 pm

I’m about to be running a Walbro 450lph internal pump in my ‘00 ranger build, and want to run a 10gauge power wire to the pump from my back battery. Seems most logical way would be to intercept original power wire after the connector that’s before the pump lid, send it to ignition terminal of a new relay connected to second battery, send larger gauge power from said new relay to fuel pump; 10-15a fuse on ignition wire, gotta check what amperage I should be looking at for everything, fuse immediately after new relay output to fuel pump, and fuse immediately as wire comes out of fuel hangar lid from fuel pump. Want to be extra precautious since it’s all aftermarket fuel system now. Read a sticky on another forum about a fuse not being close enough to the battery and the efan controller melted the truck. Figure same thing could apply to a fuel pump haha. I was just going to run a new wire from fuse box relay but then that bypasses all safeties for the fuel system. I’ll leave this in tact until the truck has suspension work then I imagine I’ll have to bypass the inertia switch to keep it from popping while off-roading. I still have that wire ran through there but will leave it bypassed until I need to eliminate the inertia switch and whatever else is between the engine bay relay and rear connector.

Comments, questions, second opinions? Want to get this engine dropped back in the truck ASAP and fuel system is about the last thing I gotta finish up. Anxious to hear this beast roar! Hope my explanation was coherent enough. Tried to be as thorough as possible. Just want to do this right and do it once. Had questions about using different gauge power wire inside the fuel tank vs outside, and if that would cause any issues.

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Re: Upgrading wiring for fuel pump?

Post by jsa » Mon Nov 05, 2018 3:24 pm

Find out what current draw that pump will have at highest gauge pressure.
Look at existing wires sizes, terminal ratings and relay ratings end to end.

It'd be pretty violent offroading to trip the inertia switch!
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Re: Upgrading wiring for fuel pump?

Post by DRod » Mon Nov 05, 2018 3:32 pm

jsa wrote:
Mon Nov 05, 2018 3:24 pm
Find out what current draw that pump will have at highest gauge pressure.
Look at existing wires sizes, terminal ratings and relay ratings end to end.

It'd be pretty violent offroading to trip the inertia switch!
According to Walbro webpage the 450lph model draws 15amps at 60psi @ 12volts(engine off), and 17amps at 60psi @13.5volt, so would it be ok to power with stock Ranger 20amp fuse/wiring system? 60 is what I would be running it at as well. System is 10an feed from tank, splits to dual 8an to go to each fuel rail, then pressure regulator “after” the fuel rails with return back to tank. Drilled and tapped pump lid for 10an & 8an bulkhead fittings and cut off and sealed all old connections.

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Re: Upgrading wiring for fuel pump?

Post by jsa » Mon Nov 05, 2018 3:56 pm

Ford will have oversized the fuse and wiring to the oem pump to allow for inrush current when the pump starts. Motors draw 4 to 8x current on startup which can trip a fuse on startup.

You need to suss out the oem connector terminal current rating. See if they can cope with 17A continuous load.
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Re: Upgrading wiring for fuel pump?

Post by DRod » Mon Nov 05, 2018 8:39 pm

It’s starting to sound more like I should just add a relay at the rear battery that’s triggered off the stock fuel pump positive wire. I could be mistaken here because I haven’t had a chance to verify yet, but I believe that fuel pump + wire leaves engine fuse box, goes to cab to inertia switch, goes to body connector to fuel pump connector then to fuel pump. Would there be an issue with running a 10 gauge wire to the fuel pump lid wire leaving about 2” stock before the lid, and where the other 4” of it inside the tank is only 12-14 gauge? Have heard about issues from using different gauge wiring causing a sort of fusible link reaction and I definitely don’t want that happening to any of the wire inside of the tank. The walbro pump itself has same 12-14 gauge, about same as the truck wire. Surprised they used such small wiring since it pulls ~17a

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Re: Upgrading wiring for fuel pump?

Post by jsa » Tue Nov 06, 2018 4:40 pm

DRod wrote:
Mon Nov 05, 2018 8:39 pm
It’s starting to sound more like I should just add a relay at the rear battery that’s triggered off the stock fuel pump positive wire.
That is a good option if your can't determine suitability of the existing circuit.
Would there be an issue with running a 10 gauge wire to the fuel pump lid wire leaving about 2” stock before the lid, and where the other 4” of it inside the tank is only 12-14 gauge?


It would only be OK if the conductor is of sufficient size for the current. 12 to 14 means probably to probably not, depending on the insulation type. Inside the tank, when wetted by fuel the wire will be cooled, so that helps your cause.

The other concern is the terminals in the connector that goes through the fuel pump lid. You need to suss out what they are and their current rating.
Have heard about issues from using different gauge wiring causing a sort of fusible link reaction and I definitely don’t want that happening to any of the wire inside of the tank.
The cause is exceeding the current capacity of the wire. The smaller piece just happens to be the lowest current capacity. Bit like replacing a fuse with a nail, the circuit becomes the fuse.
The walbro pump itself has same 12-14 gauge, about same as the truck wire. Surprised they used such small wiring since it pulls ~17a
The insulation on the walbro wire uses a higher grade material that can operate at a higher temperature and therefore higher current. It is also fuel cooled some of the time.
Cheers

John

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Re: Upgrading wiring for fuel pump?

Post by DRod » Wed Nov 07, 2018 11:23 am

Are you familiar with the fuel pump style on the rangers? Does the ecu run the pump at different power levels depending on situation or since this was an internally regulated “returnless” system, did it just run at a constant level?

Suitability of current system seems plausible, it’s fused for 20a, and I’m sure they leave a buffer zone in the wiring that makes it capable of supporting more than its fused for. But that’s why I’m here double checking haha

There isn’t a connector that goes through the actual fuel pump lid, it’s just a plastic snap in piece that has the sending unit’s wires, ground, and fuel pump wires sealed through it. There is a connector that’s on the fuel tank subframe that has about 5” of wire after leaving that connector before it hits said plastic piece where the wires go through.

Concerning wire size, there would be only about 2”-3” of stock gauge wiring left through that white plastic piece if I replaced it with the 10ga feed wire. I would also add a fuse on the end of that 2-3” of stock wiring that’s left if I took that route. The only other wiring that’d be left is the wiring on the inside that’s used on the connector walbro provides with their pump to splice in to the existing harness.

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Re: Upgrading wiring for fuel pump?

Post by cgrey8 » Wed Nov 07, 2018 11:50 am

I don't have much to add on this other than to comment about the pump size. 450lph??? You are going to need that much?

I run a 255lph in my truck and it was a drop-in replacement for the factory 88lph Walbro. The only positive I can say about it is the TREPerformance pumps are quieter than Walbro...by a significant amount.

My setup is an 89 Ranger return-style system. But the tank configuration should be very similar to any truck...a long and thin gas tank with the pump/sending unit mounted in the center of the tank. What I don't like is how it tends to suck air at the most inconvenient times. Even the 155lph Walbro I had in there 10 years ago did this. If I let the fuel level get much below 1/2, I have to be really careful taking hard-accelerating turns or even WOTting it straight. What happens is all the fuel slams to the back of the tank, leaving the pump in the center of the tank sucking air. Before I can complete the turn, the engine will bog and die. It takes it a good 3 seconds for the pump to re-prime and restore fuel pressure. As you can imagine, the transition from 1st gear acceleration to 1st gear engine braking is quite abrupt which causes the fuel to rush from the back of the tank to the front leaving the pump to continue sucking some air. Even a tiny amount of air is going to kill fuel pressure since air is compressible and the fuel pump isn't designed to produce pressure with air. So as a result, I've had to learn to simply not 1st gear WOT the truck if I'm less than 1/2 tank. It's REALLY bad if I WOT it on a 1/4 tank.
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Re: Upgrading wiring for fuel pump?

Post by DRod » Wed Nov 07, 2018 12:53 pm

Plan is 750-800hp on boost. Want to have more than enough and be sufficient for that level on e85 as well, and since the regulator will be boost referenced, I’ll be running more than the 60psi setting when hard into boost.

I’ve had the same issue with my walbro 255 pump in the previous build. Quarter or under + WOT = ignition cut, mine would never stall but would cut power for 1-2sec as engine idled down then resume running and responsive to throttle input. There any fancy ways to prevent this without going to a fuel cell?

Do you know how the factory pump is controlled in the returnless trucks? Is it one set speed it’s run at or is it a 2 speed/variable speed setup?

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Re: Upgrading wiring for fuel pump?

Post by cgrey8 » Wed Nov 07, 2018 2:49 pm

In the 98-01 Explorer 5.0Ls, it was an in-tank return which gave you a returnless-appearing system by only having 1 line going from the tank to the engine bay. But the EEC didn't modulate the pump. It ran just like a traditional return-style. I suspect the Rangers would work the same, but I can't say that with absolute certainty.
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Re: Upgrading wiring for fuel pump?

Post by DRod » Wed Nov 07, 2018 3:11 pm

Well I’m running a 98-01 ecu in my ranger so I assume it’d be the same unless there’s hardware between pump relay and rear harness connector which all I saw was the inertia switch; and yes exactly, the return was from the fuel filter and regulated to 350kPa internally right next to the pump.

What would be the best way to bridge the gap between stock gauge positive pump wire and the 10ga I want to feed it? Heatshrink crimp connectors? Is it ok to leave ~2” of the stock wire in place, say 1” on top side and 1” inside tank side of the fuel pump lid? I had cut them off short and used the wires from the harness connector walbro provided so it’s a plug connection to the fuel pump.

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Re: Upgrading wiring for fuel pump?

Post by jsa » Wed Nov 07, 2018 3:23 pm

DRod wrote:
Wed Nov 07, 2018 11:23 am
Are you familiar with the fuel pump style on the rangers?
No I am not familiar with a ranger fuel system.
Cheers

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Re: Upgrading wiring for fuel pump?

Post by DRod » Wed Nov 07, 2018 4:09 pm

jsa wrote:
Wed Nov 07, 2018 3:23 pm
DRod wrote:
Wed Nov 07, 2018 11:23 am
Are you familiar with the fuel pump style on the rangers?
No I am not familiar with a ranger fuel system.
No worries; cgrey answered my question about if the ecu modulated the fuel pump or not and it appears it doesn’t. Makes the secondary relay option more feasible.

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Re: Upgrading wiring for fuel pump?

Post by cgrey8 » Wed Nov 07, 2018 4:58 pm

I do believe the Explorers did run a vacuum line back to the in-tank Fuel Pressure Regulator so it could modulate with manifold pressure the way a traditional FPR works.

Otherwise the EEC would have to monitor both fuel line pressure and manifold pressure to compensate for the indifference when it calculating the injector pulses. And I'm fairly confident none of the Explorer 5.0Ls had a fuel pressure sensor the way the variable speed returnless systems do.
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Re: Upgrading wiring for fuel pump?

Post by jsa » Wed Nov 07, 2018 5:07 pm

DRod wrote:
Wed Nov 07, 2018 11:23 am

Suitability of current system seems plausible, it’s fused for 20a, and I’m sure they leave a buffer zone in the wiring that makes it capable of supporting more than its fused for. But that’s why I’m here double checking haha
I don't share your enthusiasm!
Size the fuse to handle short term startup.
Size the circuit to handle long term actual load.
Ensure fuse blows under short conditions before insulation fails.
Save a pittance on wire and terminal rating.
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Re: Upgrading wiring for fuel pump?

Post by cgrey8 » Wed Nov 07, 2018 7:06 pm

jsa wrote:
Wed Nov 07, 2018 5:07 pm
I don't share your enthusiasm!
Size the fuse to handle short term startup.
Size the circuit to handle long term actual load.
Ensure fuse blows under short conditions before insulation fails.
Save a pittance on wire and terminal rating.
Good points...
...Always Somethin'

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Re: Upgrading wiring for fuel pump?

Post by tvrfan » Thu Nov 08, 2018 1:06 pm

Just seen this thread.

Don't ever forget the three principle points of large scale manufacture for pretty much everything, including cars and white goods.
C-A-N = Cheap. Adequate. Nasty.

These guys all shave every last dollar they can from everything. No, that's not cynical, that's business. How to make a profit.

So the fuel pump wiring will typically be "adequate" for a standard pump. If you are doing any work, for the cost, put in a nice thick wire (at least one size up), and then you will know you've got extra capacity. I would consider that even for the standard pump. Keep the fuse the same rating if it's the same pump, the fuse protects the pump as well as the wires (and your safety). If bigger pump, don't go up a huge amount, otherwise fuse won't blow first, which is the point.... the other thing is don't forget to have a really good earth return to the body.

I've built a few kit cars in my time, and rebuilt a good few fibreglass cars and it's amazing how much brighter the headlamps can be with thicker wires and proper connections and earth returns (can't use the body if it's plastic...).
TVR, Triumph (cars), kit cars, classics. Ex IT geek, development and databases.

https://github.com/tvrfan/EEC-IV-disassembler

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Re: Upgrading wiring for fuel pump?

Post by DRod » Fri Nov 09, 2018 2:58 pm

So that’s a definite on having the stock system trigger a dedicated relay from my back battery to provide a dedicated 12v to the fuel pump. Will have a fuse on trigger wire feeding new relay. I’ll grab some good 12ga so it’s not as much of a jump from new positive wire and stock that’s fed through the fuel pump lid. I’m going to get a same-gauge-as-stock in line 20a fuse, tie the wire together with stock pump positive about 1” from exiting the top of the fuel pump lid, lay some solder over them both, good electrical tape and some good heat shrink over that. Opinions, comments, or concerns with that logic? Reason for some electrical tape under heat shrink is you can see if there’s been a lot of heat buildup at the contact area. Have done this before with some stereo connections and it provided some insight, so curious if it will do the same here, if there is any heat buildup.

Already upgraded ground coming from fuel pump connector above gas tank and from fuel pump negative. Have a good stereo system so frame, body, and engine are all grounded very well to both batteries.

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Re: Upgrading wiring for fuel pump?

Post by cgrey8 » Fri Nov 09, 2018 3:10 pm

I get not wasting money or time, but you are talking about a 800hp build. This isn't a place to skimp. Do it right when it comes to getting the fuel from that pump to the engine which includes getting the "angry pixies" from the battery to the pump.
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Re: Upgrading wiring for fuel pump?

Post by DRod » Sat Nov 10, 2018 12:09 am

cgrey8 wrote:
Fri Nov 09, 2018 3:10 pm
I get not wasting money or time, but you are talking about a 800hp build. This isn't a place to skimp. Do it right when it comes to getting the fuel from that pump to the engine which includes getting the "angry pixies" from the battery to the pump.
The only part being “skimped” really is the 2” of stock wire that is integreated in the plastic little clip that goes in the fuel pump lid. There’s only maybe 2” of it before it’s the walbro wiring harness adapter, and the other end would be to a high quality 12ga wire from a secondary relay. Would that not work ok since it’s such a short run of the stock wiring? Ground is good to go, it’s grounded to frame and back battery.

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Re: Upgrading wiring for fuel pump?

Post by cgrey8 » Sat Nov 10, 2018 7:39 am

You might be fine. If you know for a fact that piece of wire will handle the current, then roll with it.

But if there's a chance that it'll cause you problems, then drill out the studs or rivits or whatever is transferring the connection from the outside of the tank to the inside so you can install a wire that's beefier. And because you are talking about a wire that's inside the tank, it'll obviously need to be wire that's rated for that environment. If the new pump is reusing the spade connector, then that'll need to be spec'd for gas-tank installations as well.

I didn't think 2nd about installing the 255lph pump that I have and reusing everything else that was stock. Since it wasn't any where near the current consumption of the wire's limits, it's never been a big deal. And I'm not running it on a boosted engine which would run the fuel pressures way up (and thus the electrical current up with it). But in your case, you'll be doubling my pump's side AND stressing it with a high demand. I don't know if that changes the dynamics enough or not. But the thought of a wire charring inside of a fuel-rich environment wouldn't leave me feeling super-confident.
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Re: Upgrading wiring for fuel pump?

Post by DRod » Sat Nov 10, 2018 4:16 pm

https://www.highflowfuel.com/i-10388151 ... gLgUPD_BwE

As you can see the wiring they provide from the pump an the harness connector walbro provides as well is somewhere from 16-14ga. Nearly the same size as the fuel pump lid, or exactly the same size. I figured if there was one piece of wire to leave potentially inadequate, it’d be the one that is least exposed in the tank area (the only remaining stock piece of wiring. I picked up more wiring supplies to make a 12ga power wire to the walbro wiring harness adapter and get rid of the stock 2” piece of wire in that plastic clip.

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Re: Upgrading wiring for fuel pump?

Post by cgrey8 » Sat Nov 10, 2018 6:20 pm

That's nice that they actually give a molded plug as opposed to the spade connectors. As a general rule, I don't trust spade connectors...but mostly that's only due to my experience with the cheap ones. The quality that manufacturers would use are designed much better and don't fail the way the cheap ones due...not generally. Regardless, this one has a proper connector which I find far more reassuring.
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Re: Upgrading wiring for fuel pump?

Post by DRod » Sat Nov 10, 2018 8:12 pm

cgrey8 wrote:
Sat Nov 10, 2018 6:20 pm
That's nice that they actually give a molded plug as opposed to the spade connectors. As a general rule, I don't trust spade connectors...but mostly that's only due to my experience with the cheap ones. The quality that manufacturers would use are designed much better and don't fail the way the cheap ones due...not generally. Regardless, this one has a proper connector which I find far more reassuring.
It was nice to see a sealed plug and sealed wires going to the pump. Would be nicer to see larger gauge wiring, but if they think it’s sufficient then so be it. I’ll just extend the wiring harness adapter wires through the fuel pump lid and splice 12ga to them. That’s what had me questioning everything was the gauge of wire they supplied with the harness adapter. Literally the same as stock lol

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Re: Upgrading wiring for fuel pump?

Post by DRod » Sun Nov 11, 2018 7:26 pm

Using a few different wiring gauge calculators, it seems a 14-16ga wire that’s extremely short can withstand quite a bit of amperage @12v. Seems like a 14-16ga wire would be unsuitable to a 30a max pull is if it’s 2ft or longer. Here’s the one I was using, curious if you guys find it accurate in your opinion or not: https://www.wirebarn.com/Wire-Calculator-_ep_41.html

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Re: Upgrading wiring for fuel pump?

Post by jsa » Sun Nov 11, 2018 8:13 pm

Two different ratings in play, current carrying capacity and voltage drop.

Short lengths of thin wire are ok with regard to voltage drop, BUT only if the cable can be kept cool enough so the insulation does not fail.

If you use Tefzel you could run it at 150ºC, but basic PVC is good for 75ºC. Other cable types are in between.

First off the cable must be rated for the current it must carry.
Second, you may need to increase copper cross section to keep voltage drop low enough.
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Re: Upgrading wiring for fuel pump?

Post by DRod » Tue Nov 13, 2018 12:42 pm

Current carrying capacity is what I was curious about. With that voltage calculator thing you can set what % loss you want and what length would keep it within that percentage.

I guess one way I could see about the super small length of stock wiring that’s the same characteristics as that supplied by walbro, is seeing what the lightest fuse I can run before it pops it on initial startup. My goal is to see what amperage will pop the fuse on startup of the pump, and see where that lies in relation to how much current the smallest wire can/should carry. I have a voltage monitor that was used in my old stereo systems that I can hook up to the pumps positive wire so I can see real time what voltage drop looks like and when it starts dropping if it does. Native batt voltage drop should be minimal, since I have a 280a alternator and two optima red top bat’s, dual 1/0 OFC charging from alternator, 2/0 OFC ran from front bat to back bat, back bat is grounded to front bat, bed, and frame. Running voltage even with my radiator fans and trans fan running sits right at 13.5-13.8

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Re: Upgrading wiring for fuel pump?

Post by cgrey8 » Tue Nov 13, 2018 1:13 pm

Where are the batteries located? I'm assuming you relocated one to the bed? Or did you find a space under the truck somewhere?
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Re: Upgrading wiring for fuel pump?

Post by DRod » Tue Nov 13, 2018 1:49 pm

Yessir one in engine bay and one in the bed, I’m going to be moving the back one inside next to the subs to condense some wiring and clean some stuff up. Minimize amount of wires entering truck from back battery hopefully to only the two for power and ground. Going to set up a fused 10-12g 4 bay distribution block just outside the cab for both power and ground, since I have a compressor that’s in the bed as well; new relay for 12g fuel pump supply will be ran from that distribution block being triggered by the stock positive wire from the native harness, and pump will be grounded to that back battery as well as the frame where the gas tank is grounded too.

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