Alright so here's what I got. New fuel pumps in both tanks. New fuel filter. Did not replace high pressure pump or pressure regulator yet. Truck will turn over but not crank on its own. I can spray fuel in the throttle and it fires like a champ. With key on and each tank selected by dash switch, the pumps in the tanks are getting over 8 volts. I pulled one injector plug and with ground lead on battery, key on- both female slots in injector plug give battery voltage. Any ideas or troubleshooting steps to finish this up? Also put a pressure gauge on the rail. Won't run so can't get a read on static pressure but when cranking pressure doesn't register on gauge, needle barely moves and very little pressure releases when I hit the relief valve.

 

I'd start with the fuel pumps. Do you hear the rail mounted pump running when you cycle the key?

 

So fuel pressure was staying low and erratic. Replaced fuel pressure regulator. Used jumper wire to engage fuel pump at the relay. Relay wasn't sending voltage to pump with key on, replaced fuel pum relay. Now if I turn the key back and forth to build pressure the truck will crank and run but pressure still fluctuates and truck won't stay running long. Only piece in fuel system not new is high pressure pump on frame rail but I do hear it engage when I hit the key. Should I go ahead and replace this or is there anything else to check?

 

Might check for a scrody connection at the high pressure pump before you shuck out more bucks.

 

What is your fuel pressure at?

 

So here's where I stand: so far have replaced both tanks and sending units, filter, pressure regulator, relay and now high pressure pump but still wasn't getting hardly any fuel pressure either by turning ignition or using jumper wire at relay. I'm getting voltage to in tank pumps when corresponding selector valve to tanks. High pressure pump will pull up to 40psi when back end of pump is hooked to hose that is in a fuel can. Truck runs fine when I can get fuel delivered to engine. Only part not new in system is selector valve. I have good connections at the high pressure pump. Battery is hooked to charger to ensure good voltage. I am almost to the point of lighting a match.....any ideas what this gremlin could be? Oh yeah when whole system is hooked up together only getting about ten pounds of pressure max.