ksg5000 wrote:
Here's a thread that might help. https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/24187681/print/true.cfm
Amazing you found that old thread, Kevin! Your search skills are way better than mine! This is the Dual Tank Fuel System Diagram the thread talks about.
We sold our coach with that chassis, 1983 E450/460, back in 2008, so memory has faded. Notice "Starter Relay" in the upper right of the diagram. When CRANKING, that Light Blue Fuse Link wire is energized. This runs the selected Fuel Pump WHILE starting, before the Oil Pressure Switch is satisfied. You can use that as a test point. Engine NOT running, pull that lead off the fender mounted "Starter Solenoid" and power it with a test lead. You should hear one of the Pumps run. You can also install a "Primer Circuit" to use that for filling the carburetor float bowl after the coach has stood and it dried up.
This Light Blue Circuit also bypasses the Resistor Wire. I think Ford intended the Pumps to run at a lower voltage than the alternator provides. For longevity. They did it with Ignition Coils too. The Resistor was bypassed in Start. Since Starter Motor is a big current and voltage draw, bypass in Start gave Pump a better chance to fill the carb while cranking.
We broke down one day, right in front of the house. That Resistance Wire had burnt out. Notice it's WIRE not a Ceramic Resistor as used by some, so hard to find. Wrapped in a Harness, it's labeled "Do Not..." I forget just what but you can't splice it.
If it starts then runs out of gas, it's likely most of the system is OK except what's bypassed in Start and it's run out of gas provided by Light Blue in Start.
The linked thread is long, and confusing with all the dead links. So let me offer to help now, and add that you CAN pull fuel through the in-tank pumps of this era when they are not running. This means you can conceivably tap into the supply lines with an aftermarket 5-7 PSI electric pump. The newer Fords with High Pressure in-tank pumps will NOT allow that. Tank has to be dropped and Pump replaced. But the pumps used with carburetors will let you do that.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB