When driving for a bit at 70 mph. Headlights, dash lights, and radio start to cut in and out. Alternator has been replaced. When idle I've tested the battery and alternator stationary, everything turned on, and over 2000 rpms. All pass.
I also have this other issue where everytime I get gas my car wont start, it takes a minute to crank.
Could the fuel pump drawing too much power cause this issue?
I had a similar situation with a 1998 GMC; going down the road at 70 mph and the engine stops. Bottom line ; the battery connection (+ side) had 2 or 3 cables that fit together in a specific orientation/location. The clamp could feel tight but not get power. Loosening the clamp and slight rotation permitted the cable ends to fit together and every thing was fine for the next 4 years (when it was sold). I do not understand it.
This sounds to me like you have a fuel problem.
The first thing to do is to look at the fuel filter to see if this is clogged up,this is typical when your car looses power when driving.
The second thing is to see if the fuel pump give the right amount of fuel at the right pressure,to diagnose this you need to take of the fuel hose(put the end of the hose in a bottle to collect the fuel)turn on the ignition to see if the pump is running and producing a good fuel flow(in most cars the pump starts when you turn on the ignition if not you need to run the starter for the pump to start).
The last thing is to take a look at the electrical system,bad battery-loose connection-charging system,focus on the battery connections and the grounding as this is often the cause for problems.
Check the ignition switch. Does the ignition switch have a position where the engine can run but the headlights and other accessories turn off? Turn it slowly to start with the car in drive so it won't crank and see if those accessories turn off. The the accessory part of the ignition switch could be have intermittent continuity issues.
The long cranking issue is probably unrelated since it is only happening after you get gas. Check to see if opening the gas cap without getting gas can reproduce it.
