This is on an 83 F-250, 351W. I use this seldomly as it has my snow plow on it, but when I need it - I NEED IT! I'm a diesel guy, so excuse my ignorance.
It runs OK, but when it sits for more than 2 days, it will not start w/o ether. Sounds like a loss of prime to me.
My options are:
replace mechanical fuel pump and hope that helps
remove mechanical pump and install an electric fuel pump at or near the carb
replace mechanical pump and install an electrical fuel pump before the tank switching valves

I suspect my loss of prime is coming from the tank switching network.
Usually when we get a big snow, I am on the road (truck driver). This truck needs to be reliable and simple enough for my non-mechanical wife to start and operate.

 

Before replacing the fuel pump check to see if the carburetor still has fuel in it after sitting overnight. Do this by pushing open the choke then fully actuating the throttle once. You should see the accelerator pump squirt fuel into the venturi. If you don't see any fuel you know the fuel is evaporating from your carburetor overnight.

 

Many people take the hoses off the engine. If you take the large hoses off that went to the top of the fuel bowl or bowls if you have a 4 bbl, that tends to let the fuel evaporate out of the fuel bowl faster than it normally would. If you find those large ports open on top of the carb, you can put a plug on them and see if that helps it.

 

Here's my experience converting to an electric fuel pump:

https://www.ford-trucks.com/forums/1...tallation.html

I love it. Never going back. My truck often sits for days or weeks, and fuel evaporates from the carb. I simply run the electric pump for a few seconds to refill the carb and the engine fires right up.

If you want to keep the mechanical pump and add an electric boost pump in series, that will work, too. I ran that set-up for several years before going full electric. Make sure the pump is designed to operate inline, upstream of the mechanical pump. This means the mechanical pump can draw fuel through the electric pump even when switched off. Not all electric pumps can function this way.

You had asked about replacing the mechanical pump. That's not likely to help. Even if your existing pump was barely working, the primary problem is the carb going dry when not in use. The fuel inlet on the carb sits up high, so it's not like fuel could siphon back to the tank via a bad pump.

If fuel isn't evaporating from the carb float chamber, it could be leaking down through a failed power valve. Not sure which carb you have, but on the 2150 2bbl, the power valve is at the bottom of the float chamber. If it leaks, the bowl will drain into the intake manifold and you won't see any external leakage.

 

Yes, X2 first step. If this trucks runs good and strong once started, it's a snow plow after all, then fuel pump is not indicated.

 

Fuel in the carb is evaporating because of the heat under it.
If you can put a non-metal spacer or thick gasket under carb to keep it from the hot intake manifold.

I just seen it posted, cant remember where now, of adding 1 qt of 2 stroke oil to 19 gallons of gas.
This helped with hot start issues and my help with sitting for a few days.
Could give it a try and see what happens.
Dave ----

 

Dave,

In this situation, I don't think heat reaching the carb is the main problem. Nearly all trucks in the factory configuration will have the hot carb / hot restart problem. After shutdown, the fuel sitting in the carb gets heat-soaked and foamy, making hot restarts tricky after 30-45 minutes or so. Less than that, and the fuel hasn't heated up enough to cause trouble. More than that, and the fuel starts to cool off enough to return to normal. Adding a spacer or heat shield will definitely help with hot restarts.

But if all is in good working order, we rarely hear of trouble at the next cold start, such as after sitting all night. Even if some fuel evaporated in that 30-45 minute hot window, enough fuel remains in the carb bowl for a quick cold start the next day before the fuel pump can fully replenish the float chamber.

If all of the fuel was evaporating overnight for everybody, we'd hear all sorts of griping about long crank times on a cold start the next day. Long periods of inactivity, yes, but rarely for a day or two. On my truck, if it sits only a day or two, it will fire right up without running the electric pump. That tells me enough fuel remains in the float chamber. But if it sits for a week or so, I have to run the electric pump first.

In my over-inflated opinion, I don't think there's a practical means to stop this slow evaporation. That's why I'm loving my electric pump conversion.

 

If the carb was heating up more than normal and the fuel level in the carb low then it may boil all the fuel out.
Someone did say something about the float bowl vent and if that is open and the above I can see no fuel in bowl.

Yes he needs to do a little checking if there is in fact no fuel in the bowl where it might be going, boiling away or leaking out (power valve?)
True as they sit a day or 2 it should start right up but a week I also have to crank it a lot to refill the bowl.
Dave ----

 

It is not a heat issue. Last time I had it running it didn't even reach operating temp. I moved it from the bottom of my driveway to the top. The following morning it took ether to get it going. I still suspect that it is air getting into the fuel lines at the tank switching valves or some other place. I really just need to run an electric pump to fill the fuel lines to the mechanical pump. After that I can shut off the electric pump, as long as the pump will still allow fuel to pass thru it when it is off. My wife will understand this procedure as it is kinda like glowing the plugs in a diesel.

 

Let us know how the install goes.

 

This shouldn't be anywhere near long enough for the carb to have dried out, especially when the engine wasn't up to temp.

Is your choke actually functioning properly?

 

I am with Ken on this you got something going on with the carb.
When you go to start it after sitting say over night or like above how many times are you pushing the throttle to the floor?
Depending on how cold it is you need to do it at least 1 time to set (close) the choke for the motor to start.
You are hitting the throttle once right? It is not un-heard of youngins not hitting the throttle as it is not needed on EFI motors.
You may need to push it 2 times and then hold it about 1/4 then hit the key.

But you need to make sure the choke is closing when the throttle is pushed and after sitting over night gas squirts.
If no gas you need to find where it is going and there is no way in he11 it can drain back to the tank so dont even go there as gas can not go up in to the needle and seat from the bowl.

Adding an electric pump is just a band aid.
What if the fuel in the bowl is draining into the motor and thinning out the oil?
Dave ----

 

I'll jump on the bandwagon and agree overnight is too quick for the carb bowl to go dry.

My hunch is the power valve is leaking. That will drain the float chamber into the intake manifold. You'd have no other major symptoms nor any external leakage. Two basic methods to confirm this:

1) With the engine at idle, gently turn in the idle mixture screws all the way. The engine should stall as the fuel stops flowing through the idle passages. If it keeps running, the engine is running on leakage from the power valve.

2) Run the engine briefly and then shut it off while still cold. This makes sure the carb bowl is full. Remove the carb, being careful not to tip it. Set the carb outside somewhere safe, and set it on a sheet of clean paper and check it every few hours. If the power valve is leaking, you'll see fuel stains on the paper. You may not see any liquid, as the fuel can evaporate fairly quickly, but it will stain the paper.

 

Seems if the fuel bowl is leaking into the intake manifold in a short period and the engine is still warm it would be like trying to start a warm engine with the choke on, ie flooding the engine. The OP says ether would start it though.

It may be time to rebuild the carb and replace the power valve. Verify proper choke operation first though. And check for gas down the throat after a day or two by actuating the throttle.

Something is not right...

 

Don't do it. Too many stories of the mechanical pump leaking internally, and when the electric pump is activated, it fills the engine with fuel. If you want to run a electric pump, just hook it up and run it all the time and forget the mechanical pump. Nothing to worry about if you just use the electric pump and hook it to a ignition on power wire.