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Odd Fuel issue with Supercharged Automatic

I hope this is the best place for my fuel question. I have a 2014 automatic coupe that is supercharged (Topgunz) that had been running regularly and well for over

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Old 09-18-2021, 02:04 PM   #1 (permalink)
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Default Odd Fuel issue with Supercharged Automatic

I hope this is the best place for my fuel question.

I have a 2014 automatic coupe that is supercharged (Topgunz) that had been running regularly and well for over a year with no issues and an amazing tune until more recently. About a year ago I upgraded my 340 fuel pump to a 520 walbro with cj's tophat and fuel return system with all the fixings to run e85. Things were great for Id say 4 months and then I began getting intermittent fuel errors (p0181)(p0183)(p0463)-all are fuel level or fuel temp sensor "A" circuit high and circuit range performance.

I did have an on and off again issue with error(p2138)-throttle position switch sensor error causing limp mode -long before the fuel errors and before the fuel upgrade ... to remedy this I replaced the entire pedal assembly and seemed to have taken care of this issue .........for the most part :/ (the error started coming back on occasion when my fuel pump would die) I'm unsure if there is a connection.

For the last 3-4 months my intermittent fuel errors became more persistent and my fuel pump would not prime at start up and could be verified by my mechanical fuel pressure guage under the hood reading 0 with no prime audible and only a click at the relay on start. Again, it was an off and on issue, and I went through new batteries and tried manipulating the connection to the positive lead for the power that runs to the pump and relay. I've tried many things. It became increasingly worse and would even stop working while driving as if the car was out of gas. About 3 weeks ago I had to have the car towed to my house from the hospital i work at as the intermittent issue seems to have become permanent.

As of now I've confirmed voltage at the battery, correct power at the relay, including replacing the relay to make sure, I've confirmed power through the top hat and down to the pump. I replaced the pump and have the same issue. Just a click, funny thing is I can take the housing out and connect the pump to a positive and negative on the car battery and both the old and new pump spin right up. So....what am i missing?, voltage maintains all the way down the line south of the battery to the pump in the housing that can be read for a split second when i turn on the pump from the ecutek software, but the pump will not spin up. only if it's directly connected to a power source. The relay is obviously reading correctly it has the correct voltage. I also believe the pink cable that comes from the car that comes in to the relay and out has voltage. I'm at a loss. Is there an additional piece that helps prime the fuel pump in an automatic? Any words of advice would be greatly appreciated. Thanks,

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Last edited by Sed8u; 09-18-2021 at 03:31 PM.
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Old 09-18-2021, 04:05 PM   #2 (permalink)
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I'd say it's for sure a wiring issue. The fact that it's intermittent I don't think you can completely rely on manually checking voltage. Along with fuel pump power, the fuel level and temp sensors are also in the same wiring bundle that goes through the top hat which leads me to suspect the problem is probably there. I would take apart the connectors inside and outside the top hat and make sure everything is still pinned correctly and not loose.
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Old 09-18-2021, 06:00 PM   #3 (permalink)
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You say you’ve confirmed power through the top hat to the pump. This makes me ask the question how? I’m assuming a digital multi meter? If so you may have just discovered one of the limitations of a dmm or logic probe that can bite a lot of people in the ***. They only do a sample of voltage but they are high impedance and do not show if the wiring is able to supply the needed current (example you will never detect a highly resistance ground by just checking voltage at the pump). So you’ve confirmed you have voltage to the pump, great now check ground voltage drop, use a read test light clipped to ground and see if the power side can light the light, or even better if you have a power probe supply your own ground at the pump and see if it spins, if not then Supply power. You need to find which side is having the resistance.
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