Mustang5L5’s progress thread - Rear window fun

FastDriver · Nov 26, 2025

GSS307 or GSS340... either way a 255LPH. Swapped it right before dynoing on nitrous just to be safe.

Mustang5L5 · Nov 26, 2025

Thanks. I’ll hold off for now. Since it wouldn’t be apples to apples I have no idea if it will tell me I have a pump issue or a restriction elsewhere.

I started working on voltage testing. With the pump disconnected I get battery voltage at the plug. Was hooking up the lines for the return and it went going on right. Of course I forced it and buggered up the seal

So $64 for a new one incoming. The feed line is original so might be a good idea to just replace both.

Needless to say, I have to stop for now.

Kid wita 5oh · Nov 27, 2025

I have a 190lph walbro pump sitting on my shelf. if you want it, you can have it. Remember, i'm only a town away

was in my car for a season before I did the full fuel system

Mustang5L5 · Nov 28, 2025

Kid wita 5oh said:
I have a 190lph walbro pump sitting on my shelf. if you want it, you can have it. Remember, i'm only a town away

was in my car for a season before I did the full fuel system

Damn, that would actually be convenient. That might help me out a ton just to swap the pump out real quick.

I have a few things else to check, but I'm not entirely sure the pump is to blame yet so a quick pump swap would rule that out. I'll send you a message later on. thank you!

Mustang5L5 · Nov 28, 2025

Ok folks. Wanted to perform a voltage drop test under load.

So, i charged the battery overnight to 12.4volts. I connected a lead from neg side of the battery to the back of the car with my multimeter set on voltage connected to that lead, and to the neg side of fuel pump connector. I did it first for neg, and then swapped to the pos side.

12.4 Volts battery

Neg voltage drop test: 0.3 volts
Pos voltage drop test: 0.7 volts.

SO about 1.0 volts of drop. This would scale up higher if i did the test at 14.4 volts.

So if i use the previous posted voltage/flow chart and scale to 11 volts at 44psi, it's around 31-32 GPH, which is about 1/2 gallon of gas per min at 12volts. Thats what i got when i did the flow test.

So....wiring problem?

AeroCoupe · Nov 28, 2025

Isn't their a connector in the driver kick panel and then there is the one back at the tank. Maybe do drop tests at these two locations and see if the results are any better?

Mustang5L5 · Nov 28, 2025

I started down that path. Decided to measure resistance in the wiring.

Got some prelim numbers but I need to pull the driver's seat to get to the relay.

Kid wita 5oh · Nov 28, 2025

Mustang5L5 said:
I started down that path. Decided to measure resistance in the wiring.

Got some prelim numbers but I need to pull the driver's seat to get to the relay. It does look like whatver my issue is, is on the POS side.

Just do the relay and 10 or 12g wiring upgrade if you suspect ANYTHING wrong with stock wiring

....I know ...

Mustang5L5 · Nov 28, 2025

Got about 0.2 ohms of resistance on each leg. So 0.4 ohms for the entire circuit. A bit high as it should be around 0.08ohms (total both sides) given the OE wire size and length of run.

I should really throw the pump back in the tank and run it under load again and take a current reading. I think that number will give me my answer. Also, for the hell of it i should run it with and without this sock full of crud.

Need to start thinking of a clean way to run a wiring circuit back here and trigger it off the stock pump wiring. I hack hacked up wiring so will need to think this through.

Kid wita 5oh · Nov 28, 2025

Over thinking it.... Run a dedicated hot, fused, and ground from the battery(10g or 12g for both)to the back, to a relay, trigger the relay from the stock wiring in the hatch after the inertia switch, then the same 10 or 12 down to the pump ...I would run it through the hat and to the pump (if you buy the coated wiring that can be submerged)

There's a bunch of good videos on you tube of it as well, Neomustangs comes to mind

Mustang5L5 · Nov 28, 2025

Got 10g wiring and a 75a relay. Just need to figure out the pump connection details. Will surf around YouTube a bit and see what I can learn.

Kid wita 5oh · Nov 28, 2025

75a is overkill but I like it lol

Mustang5L5 · Nov 29, 2025

I just happened to have it. Need to grab a few other odds and ends like overcurrent protection, and maybe a delphi weatherpack so i can make a disconnect at the fuel pump. Saw neomustangs video and that answers the question on how to get 10g down to the pump itself. Now just trying to see how i can extend the return down like the aero motive hangers do to avoid aeration of the fuel. Also have a new fuel pump sock on the way.

Needless to say might need some time for the next update to get this all wired up so stay tuned

Mustang5L5 · Dec 1, 2025

One small update. Now diaphragm for the Kirban arrived. Switched that out and reinstalled it. So engine bay is all buttoned up now.

Still waiting on some parts before I pull the drivers front fender liner and start running 10g to the back. I want to run a CB so trying to figure out a clean way to run it. I have a distribution block inside the fender so not a stock wiring situation there.

Mustang5L5 · Jan 7, 2026

Had to dig back into this forum to find this thread. I haven't done anything to car since early Dec. But now that the holidays are over, I can dig back into it shortly. I have a box of parts and need to get this fuel pump circuit run. So just need to plan a day, fire up the heater (because it's cold here now) and get at it.

Had some plans for some MS-related Youtube vids I need to get back on. If i don't get cracking now, it will be April when i start working on the car vs getting ready to drive it.

hoopty5.0 · Jan 7, 2026

How is YT going for you? I finally got monetized but its tough keeping up with making videos. I need income for car parts so here I sit editing, LOL

Rdub6 · Jan 7, 2026

hoopty5.0 said:
How is YT going for you? I finally got monetized but its tough keeping up with making videos. I need income for car parts so here I sit editing, LOL

What’s your channel?

hoopty5.0 · Jan 7, 2026

Rdub6 said:
What’s your channel?

Colsch Craft

Mustang5L5 · Jan 7, 2026

hoopty5.0 said:
How is YT going for you? I finally got monetized but its tough keeping up with making videos. I need income for car parts so here I sit editing, LOL

Consistent $50/month into my pocket. Can't complain about that too much. I haven't made a video since summer. I really need to get back on that as I have some good ideas but just need to put the time into it. I just got some better editing software so hoping to improve quality of vids moving into 2026.

Overall feedback and engagement has been positive. Only a few negative folks.

hoopty5.0 · Jan 7, 2026

Right on! Im making a little bit more than that but not by much. Premier pro is great but Im not putting time into learning the program like I should. My goal for this year is to keep cranking out content and get to $500/mo or better. Car parts are expensive!

Mustang5L5’s progress thread - Rear window fun

I was uncomfortably high & wearing a helmet

That is…until I whipped out my Bissell

I'm definitely not in the original hole

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

I'm definitely not in the original hole

That is…until I whipped out my Bissell

I'm definitely not in the original hole

That is…until I whipped out my Bissell

I'm definitely not in the original hole

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

mechanicus terribilis

So while I wait to figure out my rear end issues

mechanicus terribilis

That is…until I whipped out my Bissell

mechanicus terribilis

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