+1 - and Silva.
After you get her/his trust a bit, try putting food in your car with door open and back away. Don't push the stress factor in any way. The dog obviously has issues. Let the dog dictate the parameters.
You might also try just sitting down with or without food nearby and letting the dog come to you.
Play posture - on your 4s, head down, butt up might be worth a try too.
