Just got our 1989 Ranger running again and found a small leak on the front side of the 17 gallon fuel tank.
I can't find a replacement tank, anyone have any ideas?

Thanks in advance.

 

1989 was first year Rangers got Plastic gas tanks, so you probably won't find any, 1988 and earlier are metal and available but won't fit.

Best bet is Plastic Welding, yes they make welders with welding rods for plastic gas tanks.

Google: plastic gas tank welding

If you can get to the leak and the area around the leak you can try epoxy/fiber mesh.
Clean and sand area well so epoxy can get a good bond to the plastic, thats the key.
You can even drill a split/crack so epoxy can penetrate the tank to get a better grip, there is already a leak there, larger hole doesn't matter but could hold better.
Layer a fiber mesh over epoxy and add more epoxy to hold mesh

Using any electrics around a gas tank, especially an empty one can be dangerous, gasoline doesn't ignite with a spark, only gasoline FUMES do, so empty tank is ALL FUMES

Always best to remove tank and clean it out with soap and water
At this point plastic welding would be best, no "ifs" if done right it won't ever leak there again