Goldhawg

iTrader: (7)

I'm almost done w/all my electrical gremlins, but one remains. My Speedhut fuel gauge doesn't work. Goes all the way to full and stays there. So I thought my sending unit was maybe bad, so I pulled the connector loose from the harness and I'm getting 55 ohm resistance reading w/tank well below full--seems about right. If I turn the key on, the resistance reads 54 ohms, and the gauge goes to just above one-half, so that seems right. When I start it up, the gauge cycles over and goes to full, and stays there. I get no reading on the wires where I'm getting a signal in the trunk; my meter automatically reads ohms/volts (smart meter fluke 7-600)--just goes to zero and no resistance beeping once running.

I am running thru the racetronix wiring harness; don't know if that has anything to do with it. I'm done for the night, but if you have any thoughts I'd appreciate it. I'll tackle tomorrow. THX!.

reedld

iTrader: (7)

Is the speedhut guage a programable or specific for your sender? I'm using the OEM 1978 0-90ohm sender...which has only two wires. Have you checked if one of the wires is loose or not connected properly at the sender? Has the sender ever worked previously?

I just did a tank swap in my 78. I went from an external pump/regulator/tank sump to a 4th gen placed into a sump. Since I did not want to buy the autometer cobalt guage specific to the 4th gen sender...or a universal programable cobalt guage, I reused the OEM sender. I had to bend the arm slightly to clear fuel bucket. With all connections in place, key on, I manually lifted and dropped float as I watched the guage thru the back window. Works perfect.

Goldhawg

iTrader: (7)

The speedhut gauge is programmable, and I have it set to the correct 0-90 setting. And the gauge reads correct with the key on. However the signal changes once started. The sending unit is a stock one, but with racetronix BCA connector and walbro pump. And then it goes through their relay setup. I'll have to contact them...just can't understand how the car running actually messes up the signal.

Edit...I did verify signal changes once started directly out of the pump before the relay setup (and purple wire bypasses relay anyway).

Goldhawg

iTrader: (7)

Well, maybe w/a bit more info you can provide some clues. First, add'l info. I was wrong that w/key on, the gauge reads correctly. It does only because the fuel pump only goes for 3 sec; anytime 12v is on it shuts down the resistance signal on the purple wire. I pulled the pump somewhat out (but pump still in the gas) and read the ohms resistance on the purple wire going into the in-tank connector and same behavior, ~45 ohms until power applied and resistance goes away. I used the power probe to check the ground and I have a good ground even in the tank.

Now for those that have impala tanks and racetronix, take a look at the pictures to check my wiring. I did do one thing wrong on my initial install; I pushed the metal locking tab 180 degrees out. So I was very careful to simply repin so each of the wires went to their correct location; I double checked tonite and I'm still convinced I have each wire properly repinned to connect to the BCA in the right way. And I do have power and ground obviously correct since I run fine. And I have the purple wire correct since I get the correct ohms both in the purple wire in the tank and everywhere else on the line. So what could cause it to not work when 12v applied?

EDIT: given some more thought; I can't see how any of the wiring would be bad. I wonder if the vibration of the pump running is simply shaking a connection on an almost 20 year old sending unit?