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I just completed my Procharger install on my 94 Z28 and it's AMAZING! All is well except my fuel guage doesn't work any longer and is stuck on the half full line. I think it's has something to do with the ground wire as I tried connecting it in the same manner as the stock fuel pump is wired with one of the fuel level sensor ground wire connected to the ground wire of the pump and the other end of the ground wire to a ground on the top of the fuel sending unit. What have I done wrong?
I do have the service manual for my car and also used shbox's website, but I was hoping someone had done this mod before and could give me an idea on how I should have wired the level sensor. I think it has something to do with the way I wired the ground to the negative side of the pump which is how the stock pump is wired but I'm not so sure. Even a pic of the wiring of a stock sending unit would help I think.
Problem is there’s hardly any active members left on this site, maybe a 1/2-dozen LT1 fans. I'm trying to keep it alive but not succeeding.
I used to have a new OEM sending unit in my garage, but I gave it away about a year ago. My thought here was to measure the resistance of the level sensor circuit per Rob/Shoebox. That might provide some insight to the circuitry problem. Or, maybe the float is stuck on something. Rob does drop in once in a while, so he might provide some insight.
You mention a ground at the top of the sending unit, but I don’t remember seeing one on my stock unit. I have some photos of the sending until, and I don’t see the ground you described.
I'll take a look at the factory service manual schematic to see if it shows that ground.
If you are using the factory wiring, you should have three wires entering the top of the sending unit, through the plastic pass-thru.
GRAY - 12 volts direct to pump
PURPLE - + volts signal wire (reduced from 12 volts by a resistor in the fuel gauge) direct to level float
BLACK - single ground wire that splits in the tank, 1 branch to fuel pump, other branch to level float
That matches the photo of my OEM sending unit. I do not see any other ground wire "other end of the ground wire to a ground on the top of the fuel sending unit.".
On the other hand, I found a photo someone sent me labeled "FuelPumpMod", and it has a pump in a repaired stock bucket, red, blue, and black wires going to the pump. The black ground wire enters, and is attached to the inside of the top of the sending unit with a large bolt thru the top of the sending unit. From there it appears to split to the pump and another thin black wire .... the level sensor is not clear in the photo. Is that similar to something you did for the Walbro 450? If so, I am just not familiar at all with that conversion.
This is exactly what I was referring to. Thanks Injuneer!
The Walbro 450 has have a new wiring harness from the pump to a new 4-way bulkhead connector which requires a new intermediate wire from the fuel pump sending unit which plugs into the fuel pump wiring harness underneath and to the hotwire kit. On the new intermediate wiring there is a ground that attaches to the top of the sending unit after drilling a hole in the top of the sending unit for the ground bolt to go through. I attached my fuel level sensor to this ground along with the ground wire from the pump. I'm thinking somewhere along these two connections is my error.
I just went out to start my camaro and noticed the fuel hand is now reading at the full mark which would mean it's 3/4 full. I started the car and drove it around and what do you know.... the fuel level guage is actually working now, lol. I didn't add any fuel or anything. Maybe the float got stuck on the wires or something and got unstuck. I'll take a look at the sender and see if I need to ziptie the wires away from the float or something but wiring-wise all is well.
Crazy!
PS, thanks for keeping this site running Injuneer. You've helped me through the years as you did with others. If you ever decide to call it quits I would love to have any and all 4th gen LT1 information you have. You've sent me info on the Scanmaster which I still resource to this day. You are doing a great work. Thanks again.
