I changed the left gas cap on my road kingnow my fuel gadge light stays on.what to do

The gas cap light is a generic light that indicates an emission problem. Usually a vacuum/pressure leak within the system. The gas cap is usually the first thing to check, however may not be the problem. There are numerous sensors and lines that control the vacuum/pressure/ of the fuel vapors and one of these is loose/disconnected/defective causing this light to come on. I would recommend inspecting hoses under the hood for any that may be loose/disconnected. You may also require a scan test to view sensor data to isolate the source of the light

Sorry mate, I dont know what this Gas cap is, could be the fuel filler cap, could be the car runs on LPG and it is a cap on the Gas charge line.

Probably a bad fuel sending unit. This measures the amount of fuel and sends the info to the gauges.

disconnect positive side of battery wait 20 seconds hook back up this wii clear codes if it comes back on tank to dealer for check something is wrong bad plugs need oil chang needs air filter bad gas cape some thing minor bit those things you can try to clear cold i would try gas cap first

Hi Andrew
Replace the fuel sending unit...it is faulty.
Bud

I have no idea why any parts were installed

You always check for codes & use them to
diagnose the system with the fault

You may need a professional scan tool along on a road
test to look at data as well as get caught up on some
maintenance

Check your gas cap. If the gas cap is night fitted tightly, it can cause the service light to stay on.

There is no fuel safety shut off switch on any vehicle except a ford. If you have no fuel pressure check for power to the pump. If there is no power let me know and I'll get you more info. If there is power than your fuel pump is likely gone bad. Let me know if you have any questions and I'll do my best to answer them. Thank you for using FixYa.com!

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

PO455 is a large evaporative fuel leak. A bad fuel cap is ONE of the things that COULD be the problem. Fuel system cleaning only lightened your wallet. Reading your post is confusing. Did all this start AFTER the Valvoline Wallet Flushing? If so , they left something loose or disconnected. I would find a qualified repair shop to fix the problem, and if it has anything to do with what Valvoline did, make them pay the bill.

You are going top have to pull the gas tank and change the gas guage sending unit, it is the cause of your erratic guage readings, of this I am 100% sure.