I am having weird electrical problems since replacing my electric fuel pump. Although I did not use an OEM pump, I used the appropriate after market replacement designed for my 1980 RX7.

My original pump was mounted on rubber studs attached to the rock shield. Since my new pump has a different bracket, I mounted the pump to the frame/body of the car. I wired the electrical connections so I can use the original Mazda +/- connection harness, or I can separate the negative wire and ground it directly to the frame.

Now, when I use my turn signals, sometimes both sides flash. When I step on the brake, or go into reverse, sometimes turn indicators illuminate on my dash. Plus the emergency brake light will come on and go off.

Is this due to my fuel pump? Does it need to be insulated and separated from the chassis, just like the original, or do I have a totally unrelated short in the system somewhere? If so, where do I look and how do I track it down?

Thanks.

 

"Sometimes" electrical problems are the worst to troubleshoot. Isolating the reason the symptom comes and goes is usually the first step, so you are chasing a consistent and testable problem.

If the problem is reproducible while the car is sitting in the driveway, I think the first thing I'd try is to just drop the fuel pump so it's electrically isolated, and see if the problem clears up.

I'd also check system voltage, as "wierd behavior" electrical problems generally boil down to either voltage regulation or grounding problems... and voltage is easier to check!

 

This actually sounds like a bad ground somewhere else in the system.
A buddy has a 79, and when he unhooked the radio antanae, funky things started happening. Stuff like the signals would flash both sides at once, and light up with tail lights. Turning on the lights, shut off the fuel pump. Short term quick fix was reattaching the radio antanea. Later, I found several bad connections in the wiring harness grounds, and battery ground.

 

How did you check and identify the bad harnesses and grounds?

 

Wasn't any bad harness, just bad ground connections. I checked them by tracking them down, loosening them, and cleaning/tightening.
I think the biggest issue was the battery ground on the front strut tower.