SUPER Complicated problem! Need Master Mechanic!
- Thread starter RGBody87
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I appreciate it... I did check and set the pressure with the car running. It looks like the Oil Filled gauge reads differently with a little bit of heat in the engine compartment. Unfortunately I need to order a dry gauge and see if it makes a difference. Thank you!
Update! The pump is getting the correct amount of power and amperage draw. What is the problem seems to be the wiring in the sending unit. The weatherpacks are not able to transfer the amount of electric current needed before heating up and causing resistance.. then slowly cutting the power to the pump. Fans and rest of power continue to run fine!
While running I have the car turned up to 6 LBS of pressure. The car then continues to drop in pressure after about the 10 minute mark of idling. By 15-20 minutes it is reading 0-1 lbs. Thinking the sending unit is the issue here.. but I am having a very difficult time running a high flow/high pressure Aeromotive Stealth 340 pump through the factory GN sending unit in a GN tank through 3/8 stainless hardline to a holley regulator that steps down to 4.5-13 lbs of pressure and both feeds and returns with 3/8" lines. The problem with the return is I had to rig my own "extra" return into the tank so it did not overpressurise. LOTS of issues trying to get a sending unit with a 3/8 return in it. Does it exist? How about with the proper wiring internally? Anyone have pictures of how to correctly wire the pump to the sending unit? I feel like the power line is a 12 gauge dropping to a 16/18 gauge then back to a 14 gauge for the pump wiring.
That should be plenty for the pump on the voltage side. What's the ground side look like? Should be matched to the power side, and as short as possible. Pump and sender grounded to sender housing, sender housing to body, and tank to body.
Here's another scenario: does the pump have an internal bypass? That could be bleeding the pressure off. I ran into a similar problem with the return being too small on my 67, even running -8 supply and -6 return. You may even want to try switching the frame lines using the 5/16 as the supply and the 3/8 as the return.
Here's another scenario: does the pump have an internal bypass? That could be bleeding the pressure off. I ran into a similar problem with the return being too small on my 67, even running -8 supply and -6 return. You may even want to try switching the frame lines using the 5/16 as the supply and the 3/8 as the return.
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Currently I am running the 3/8 supply hard line (stainless). The return line now is a braided hose that's 3/8 but I replaced the factory 1/4 hard line and had to abandon it for over-pressurizing. I would have taken a risk if it were a little larger than 5/16, but I wont run a 1/4" feed line. I am messing with the idea of finding another way of running a return and dump. I now have another concern... if you look at the sending unit after I modified it, I have one returning to the bottom of the tank, the other is dumping in the top which I fear is airating the gas. I'm going to re-drop the tank this weekend and fix this demon-child. I'm just getting frustrated with the pressure issue. I'll probably just run new wires and add a rubber hose to the short return feed to the tank so that it drops at the bottom of the tank. Then drill a hole through the top and abandon their wiring. I'll seal it with JB weld maybe?
The only other options I've seen for an aftermarket sending unit would have been a GN one, which I believe has the same return line since it was fuel injected and the return pressure didn't matter, or going with something like the Aeromotive kit.... I think I'm just going to make my own at that point. I want the fuel to return so it doesn't get so hot being stalled in the engine compartment. I'll post pictures later of what I have.
Thank you again for anyone still reading this!
I'm just thinking it's overkill. I have a Walbro 190 supporting 500hp on a single carb (with the lines as described). Mine didn't have a vent port in the sender, so I teed the line to a rear vent (5/16 return in the sender & rear of the tank).
Did you remove the baffle under the vent?
It could be a junk regulator, too. Have you tried eliminating the car return by flowing it back into a gas can at the regulator? That would narrow things down a bit.
Did you remove the baffle under the vent?
It could be a junk regulator, too. Have you tried eliminating the car return by flowing it back into a gas can at the regulator? That would narrow things down a bit.
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I think this is the answer, this is way too much pump for what you need, I'll bet you are deadheading the pressure no matter what the bypass is. The Aeromotive pump is 89pgh and would supply a 890hp engine at that flow.
I agree that it is overkill for the time being, but I'm still unsure if I am staying Big block or if I am going to a LS swap. I wanted to have the tank be one less thing to upgrade should I go either way. Theoretically it should work fine if everything was working well. I'm just trying to find a "right way" to return without issues. I appreciated the feedback! That might be the answer to step down to something else... but even if I do a factory grand national pump and sending unit, that'll fix my wiring issue and only cost around $250-$300, but then the problem still lies that I need to fix the return issue so it does not over pressurize. This is the regulator I'll be running. Holley Regulator.. replaced one already because I thought faulty but now I am thinking maybe it is something else. Brand new tank - Baffle still inside (grand national tank) and brand new everything. custom rebuilt carb I just installed an hour ago... so the fuel line is not hooked up yet.
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