Hi all,
I can't explain why i 've a lot of difficulties to start the engine after sitting a day or more. I need a lot of a lot of unsuccessful attempts before the engine starts ! The engine is the 460 with two tanks and two electric fuel pumps. I thought that with electric pump the starting would be immediate but it's a pain, my '70 Country Squire or '57 Imperial starts definitely better ! And with mechanical pump ....
When hot or after a couple of hours no problem, the engine starts immediatly...

I've tried with some fuel poured in the carb, starts immediatly so i think it's a problem with pumps command (same with front or rear tank)

 

Look at the carburetor first. Sounds like the carburetor fuel bowl is leaking dry over time. During the starting cycle of your 1986 F250, the fuel pumps run only while the engine is cranking. Thus, it can take some cranking to refill an empty fuel bowl. If your carburetor has a power valve, it could be blown and allowing your fuel to be leaked into the intake. I'm sure there are other reasons for the bowl to leak to empty. (Carb experienced guys should chime in.)

Check for empty bowl by stroking the accelerator. If the bowl is empty you may get a shot of gas or two but it will quickly run dry.

If the problem were with the pump only, your carburetor in good condition would hold plenty of fuel to start the engine while the pump and supply of new fuel caught up.

 

It could be simply the choke is not working. Adding extra fuel would cover up choke that is not working exactly right. Pump the throttle while looking down the carb throat like was suggested, that will tell the tale if you have fuel or not.

 

 

Yes i've a leak i saw yesterday !!!! Arround the cover of the accelerator pump (a drop each 5 s ?)

But yesterday my daughter had another problem (whick seems the same she had one time some months ago): When she started the engine, after 5s the engine coughed then died. She tried to restart without success. I went with some friends (it was at a US cars meeting) and we investigated the carb: no fuel after several starting time (tanks were full of gazoline) !!!! We removed the fuels caps and no sound of the electric pumps when starting with front or rear tank.
So me removed the fuel pump cut-off relay and shorted the terminals (from "hot all times" and "to fuel selector valve"): now the pumps sound and work and the truck starts ! We tested the relay, seems ok, so we reinstalled it on its socket. The truck started and ran ok. We let it run because battery was weak. Suddenly after 10 mn the engine died !!! The pump didn't "sound" and the cut-off relay was hot. We removed it again and shorted the terminals, ok. So we could return to home (and removed the short when arrival ...).
I thinh i'll put a new cut-off relay, i'm not sure that it's the only cause but i can't see a problem with the selector switch or the pumps itselves which work well when powered after the relay. I must also check the starter solenoid relay because it is used when starting (through a fuse link).


But we had another problem, related or not related i don't know but i prefere open a new topic soon.

 

 

I try to locate this oil cut off switch for sale but I do not find anything ! I
I find the 1 wire pressure switch but not a 2 wires ...
I think i'll install a timed relay which works 5 or 10s (one time) when i put the ignition on. Will replace the wire coming from the starter solenoid.

 

The oil pressure switch has nothing to do with the priming mode of the fuel pumps. That is a direct wire from the starter relay mounted on the fender. The wire with the red question mark above hooks directly to the "i" terminal of the starter relay (solenoid).

 

Yes i know but i prefere priming the carb on the "run" position rather when i start the engine with the starter running. With this modification the carb bowl will be full when i start the engine. I think that all current cars (with EFI) has this feature. Note that the timed relay works only one time, after 5 or 10s it opens until i stop the engine then turn on the ignition switch

 

 

 

I've ordered a new cut-off relay and a Holley carb kit from Rockauto. While waiting for these parts i've install a standard relay with 4 wires and lugs. Also a switch which can short the relay output.
I haven't seen this 0.75 ohms resistance wire, i can trace the pk/bk wire from C120 to relay, no presence of the resistance. On another schematic it is stated than the resistor wire is only on Bronco, no resistor on F series (but it's for another engine, 5.0 L EFI)

 

 

Problem solved with a rebuild carb kit ! The accelerator fuel pump leakage is solved and now after 1 or 2 days no problem to start the engine.
But i 've another problem: a leakage which seems to be common on the 4180 Holley: the inlet fuel threads are shot and i'm not sure i could cure without find another primary fuel pump bowl (or another carb !!!). https://www.ford-trucks.com/forums/4...4180-carb.html I've found this https://allcarbs.com/product/4180-ho...wl-ford-truck/ which is cheaper than a carb ... Or if someone has a core or carb bowl ?

 

Where is is leaking eaxactly ? There is supposed to be gasket beteeen the inlet bushing and the fuel bowl. If the bushing is leaking at the fuel line then you can buy just the bushing..