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Matt, Engineer
Category: Ford
Satisfied Customers: 21997
Experience:  BEng hons Mech engineering, in auto industry 22 years
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E350: I have a 1985 E350 Ford motorHome. Can not get power

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I have a 1985 E350 Ford motorHome. Can not get power to the Electric external Fuel pump with ignition switch in the run position. Have new fuel pump relay, new fuel pump. Can hot wire the pump and it works. Also tried to hot oil pressure switch, but no work, not sure if I am doing that right.

the fuel pump relay is fed from the ignition switch by way of the oil pressure switch

the idea being that the engine won't start until there's oil pressure

so trace the wiring back from the ignition switch - checking that there's 12V present with the key in the run position and then if there's 12V present at teh oil pressure switch

its most likely a bad connection down at the oil pressure switch as this is the most exposed part of the wiring
Customer: replied 4 years ago.

It is late, will check it out Tomorrow. Will let You know.

no problem
Customer: replied 4 years ago.

I seem to have power at the Oil pressure switch, but am not getting power to the Fuel Pump relay switch. If I hot wire that switch the pump will run.


if you haven't already then replace the relay as they can seize up with age and check the connections in the relay socket for any corrosion /. damaged terminals
Customer: replied 4 years ago.

Can it be a bad oil pressure switch. I have 12v going into the switch, but no power coming out of it. I hot wired off the ignition wire at the switch to the fuel pump relay and the pump works.

Does the oil pressure have to been hooked up for power to come thru it?


yes the oil pressure switch has to enable ( via engine oil pressure) to allow power to flow through it

so yes its quite possible that the switch is faulty and needs to be replaced

a lot of people bypass the switch altogether though
Matt and 3 other Ford Specialists are ready to help you
Customer: replied 4 years ago.

I put in a new Oil pressure switch and it was no help. What is the best way to bypass it?


there should be a feed wire to the pressure switch thats grounded through the switch into the engine block

(unless your's is one of the 2 wire type where the wire feeds in and out of the switch)

but to remove the switch from the loop just ground the wire onto the chassis or engine block