I have a 1985 f350 with 460 v8 engine. The problem I'm having is can get it to start for a few seconds then it dies. I cannot get the fuel pump(s) to come on by disconecting the wire to the starter relay, turning the key to start and listen for the pump to come on as described in the Haynes repair manual. I suspect that there has been a long standing problem in that if the truck sits for a while, you have to pump the gas peddle rather significantly to get it started but it ran. Now it dies immediately. I have replaced the front tank fuel pump, blown out the gas lines, verified that the tank selector switch and valve functions, gas in the tank and oil in the engine. I would love to hear any suggestions as I'm about to start tracing every wire in the fuel delivery system and I'm not looking forward to that. Any help will be greatly appreciated.

-Roy

 

clogged cat? (full backpressure would make it stall)

 

Are you sure at least part of your problem isn't ignition-related? Some of these trucks have
a ballast resistor in the wiring... The coil & ignition system will get full voltage during
START operations but it falls back to (I think) around 7V in the RUN condition. That could
explain the immediate-dying scenario.

As for fuel delivery, I'd check the output pressure & flow rate at the carb.

 

that wire at the starter relay supplies power to the pumps while the engine is cranking, by disconnecting that wire your pumps won't run while you are cranking your engine.try hooking that wire up to a 12 volt power supply and see what happens.if it runs then the problem is most probably the oil pressure switch or the wiring to the switch.it's located at the back of the intake manifold by the fire wall.make sure the wiring at the pressure switch is connected properly.let us know what you find.

 

If it's difficult to start after sitting I'd suggest you have a leaking float bowl or accelerator pump.
You need to fill the bowl before it will start.

Haynes is wrong. The 'I' terminal will provide power to the pump while cranking (before the oil reaches the pressure switch)

Here's a couple of diagrams from Subford.

 

This truck doesn't have a catalytic converter.

 

I would love to be able to do that if I could get the fuel pump to run.

 

Hmm. Very intersting. I will give that a try.

 

Thanks for the schematics. They will help. The carb has been rebuilt several times over the years with no impact on the starting issues when the truck has sat for a while. Here's a question. Is it possible to pump the accelerator enough times to cause enough fuel to get to the carburetor even though the fuel pump is not running?

 

Before I forget I want to thank everyone for all the helpful responses. I will certainly let everyone know as soon as the problem is solved. I don't use my truck much except for hauling hay for our horses and that's why it sits for periods of time. But my horses will be needing hay soon so I'm under the gun the get this fixed. Thanks again for evryones help.

Roy

 

I have a 1986 F350 flat bed dual tanks auto, carb 460 engine, and I have the same darn problem!
Not getting any fuel to the carb, when I put fuel in the carb it runs for a few seconds and dies?

so has anyone figured out the real problem yet

Dr John O'Connor, PhD

 

First thing to check would be your inertia switch.it's in the cab of the truck at the trans tunnel on the passenger side at the fire wall.make sure the white button is pushed in.this switch is in case you get into a accident it turns the pumps off

 

Like my other 1986 I had that was not working at all, my mecahnic told my to just cut it off and splice the wires together to bypass it?

Was that sound advice or not?
They no longer make or sell new ones of those units and they are the first thing taken at the junk yards

Dr O'Connnor

 

It should still provide fuel in start.
Look at the schematic.

Once the bowls fill it will run for two or three minutes.

 

its not getting gas to the carb, I Installed a clear fuel filter and no gas is getting to it, at all?

If I put gas in the carb it runs for a few seconds?

John