I have an 88 volvo 240 and it won't stay running unless I clamp off the reverse fuel filter line...then it runs. I have replaced the filter, the fuel pump, the relay and have no idea what the problem is. If I remove the clamp from the reverse fuel system hose the car dies. Please help.

 

You have a clamp on the fuel return line (which is taking gas back to the tank)? Sounds like maybe an issue with the fuel pressure regulator ..

 

I don't know what the reverse fuel filter line is. As bubba says, if you have the clamp on the fuel return line from the fuel pressure regulator, you should check or replace the regulator. Check it by pulling the vacuum line off the front of it and sniff for gas. If gas leaks out or if there's gas in the vacuum line it's a bad regulator.