Electrical Fuel Issues, How Fun

ForeverDriven

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Alright!
Some may remember me from last fall when I made a similar post about my '97 Coyote Swap. Well, issues have persisted and I'm here again for more help!

Here is a video (it is a safe google drive link)
https://drive.google.com/file/d/1xSwJHflu91LYOqFGtR4Rh5FnCJwusGHi/view?usp=sharing

Problems:
Takes multiple key cycles to reach full fuel pressure
Pressure starts tweaking (like in the video), while gradually decreasing until the car dies.

I went from a 255lph DW Pump to a 340 LPH Aeromotive stealth because I thought the pump was the issue, also I was still having cutoff problems so why not upgrade.

I did it as professionally as I could this time. Wires are soldered and heat shrunk. I swabbed the tank of any possible debris (there was an old filler neck grommet in there? lol), and the fuel filter is still as new as when I bought the DW pump since it didn't run for long.

There are a few possible issues I can think of:
-The wiring at the relay is all crimped female-male connections. Maybe the power doesn't go through them well enough. Will try soldering them soon.
-I fucked something up in the control pack fuse box (I ran the old pump without a relay for a bit because I've been learning as I go, so I do some dumb shit sometimes)
-Wire gauge isn't big enough going to relay, but the main power wire is 12ish gauge (running off of the fuse box) and the relay receives signal from the control pack's fuel pump wire which I believe is 14 gauge. It is also wired to run through the inertia switch too so I don't blow up in an accident.

Any input would be appreciated, guys!
 

ttocs

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take a pic of the relay and connections but unless something is really off I have always connected to relays with female spades What ecu are you using? I had a similar problem for a while with mine that I finally was able to fix by bumping my fuel pressure up a hair I think from 45 to 53 psi.
 

ForeverDriven

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take a pic of the relay and connections but unless something is really off I have always connected to relays with female spades What ecu are you using? I had a similar problem for a while with mine that I finally was able to fix by bumping my fuel pressure up a hair I think from 45 to 53 psi.
It's the stock ECU that comes with Ford's coyote control packs, but it doesn't have direct reference to the fuel pressure. Fuel pressure is just hooked up to manifold vacuum.

I'll take a photo for you tomorrow and label wires n crap
 

ttocs

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when you changed the pump is there a chance that you didn't replace the S-shaped hose between it and the hat or didn't get it on tight? You can get a leak in that hose and it will loose pressure but it leaks back into the tank so you will never see it. I would put a fuel pressure gauge on the schrader valve on the top of the motor so you can see what the pressure is to be sure.
 

ForeverDriven

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when you changed the pump is there a chance that you didn't replace the S-shaped hose between it and the hat or didn't get it on tight? You can get a leak in that hose and it will loose pressure but it leaks back into the tank so you will never see it. I would put a fuel pressure gauge on the schrader valve on the top of the motor so you can see what the pressure is to be sure.
That hose is also brand new and clamped on tight, double checked it when I did the new pump again
 

ForeverDriven

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I just noticed you said the power wire to the relay was not big enough?
I have no idea if it is, I just suggested it might be. I'm not experienced with needed gauge vs length and power
 

ttocs

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If the power wire to the relay is too small it could be getting hot/warm after running for a while and causing problems with connections. The only other idea I had was if it was getting too hot and going into a limp mode? How do you know the fuel is the problem after its been running?
 

ForeverDriven

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If the power wire to the relay is too small it could be getting hot/warm after running for a while and causing problems with connections. The only other idea I had was if it was getting too hot and going into a limp mode? How do you know the fuel is the problem after its been running?

Small update, turns out the coyote control pack has a relay for the pump IN the fuse box so I took the external relay out of the situation. Immediate fuel pressure now and it doesn't die, but the fuel pressure still tweaks hard after its been running for a few seconds. I figured the fuel is the issue because I have a fuel pressure gauge hooked up to a small hydraulic hose, which lets me see it through the windshield.

However, I did find a leak in my return line, the AN fitting that connects the main return line to the regulator return line. Seems to leak more as pressure is increased, as the more I pulled on it the more it leaked. Will be replacing that.
I believe last time I bought a 1/4th AN quick disconnect fitting for it, but that seems to be stuck on there. Do you have any opinions on a good type of AN adapter for the return line/do you know the proper size of it? (On a 97). Will look it up but just wondering if you knew off the top of your head
 

ForeverDriven

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the stock to an adaptors I think normally go to a -06an

Yeah I had -06 AN on there, it was just a bad fitting I guess. The adapter ended up being stuck on so I had to destroy it to get it off. Also, I must've had the biggest brain fart when I first found the leak because the leak was actually on the fuel delivery side. This should mean replacing it will fix the issues.
 

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