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Long story short, I bought my old 99 corvette back from someone who had removed the motor, so I rebuilt one and just installed it. Now I’m having issues with the electrical. I have cleaned the grounding points and most of the connections, but am still having issues. When I connect the battery the cooling fans turn on automatically and once I put the key in the ignition, they shut off. The fuel pump is not priming unless I use a jumper wire, I’m not getting any reading on the fuel level gauge, no reading on the oil pressure gauge, and coolant temperature it maxed out even with the sensor unplugged. It seems as if the coolant sensor is grounding out and causing the fuel pump not to run, but I’m not sure about the gauges not working. Any advice would be greatly appreciated, because I’m stumped at this point.
The cooling fans should run on low speed with engine off/no key but only for one second or one minute if temp sensor reports 284 deg., its called Run-on Temp. I would be more concerned if fans don't run with key turned on and sensor reporting 284 deg. EFI. HP Tuners will show the run-on temp function.
The ECT uses a 5 volt reference and you will see that on the yellow wire with the key on and sensor unplugged...see if you have 5 volts there...normally if you unplug the ECT sensor the coolant temp will read around -38 degrees...also unplug the MAF sensor and see if you have 5 volts on the yellow wire there too with the key on...just curious...as far as the fuel pump not priming remove the pump relay and with a 12 volt test light connected to ground see if the test light comes on for 2 seconds when you turn the key on probing the terminal below…you may have a few different issues here !!…the cooling fan is most likely running because of the ECT sensor…if the 5 volts is shorted to ground the PCM thinks the engine is overheating…the ECT is a thermistor circuit and having the 5 volts shorted to ground will not damage the engine computer…trying to figure why it goes off when the key is inserted…you should also see what codes you have stored if you can.
I got this figured out last night. The small ground wire on the passenger side of the block had a hole rubbed through the insulation and was touching the starter wire. I electrical taped it, put new heat insulation on it, and moved it away from the starter and everything is working 100% again. Something so small caused so many problems.
Electrical issues after motor swap
