Classic/Antique Car Repair: auotmotive, fuel pressure gauge, dodge van

Question
I bought a 1986 dodge van B350. when I bought it, it ran fine. now it appers to be loosing fuelpressure....I change the feul pump,and all the lines,dropped the fuel tank,,,cleaned it. changed the filters,everything I could think of. It has a eletric feul pump on the rail in the front of the vehicle. In the mornings it will drive for about 6 miles or so on the highway, then it starts jumpping.I then have to stop turn the key on and let the pump regain pressure,then I can go for another three miles or so, then repeat the process.,,,,,,Could it be vapor lock?....and if so what is the remedy.    Iv'e had it to a mechanic, but to no avail.    THANK YOU,,JOHN

Answer
Hi John,
I'm not a Dodge tech but it sounds like you need to establish for sure what is failing for sure, fuel or ignition. Remove the tunnel (engine cover) and install a fuel pressure gauge (be sure to use a pressure gauge that can handle injection pressures and secure the connections) and connect a timing light on any plug wire or the coil wire. Tape the trigger down on the timing light so you can monitor the flash. Then drive the van until it gives out. Take a passenger so they can watch what dies first before the engine quits rotating.
If it is truly the fuel pressure that drops off before the engine stops rotating. I take it this is fuel injected? Did you check to see if the pump stopped first then the engine died? If so find the pump relay and then you need a wiring diagram to see which pins in the socket are the power and which is the pump. Put a temp. jumper between the power and the pump sockets and test drive the van that way. If it does not die you have either lost the trigger that activates the relay or the relay is dropping the pump.
If this does not find the problem you need to read each techs profile to find a Dodge tech.
Howard