1985 F250 460 automatic. History: my father in law and me bought this truck a couple of months ago. It has 45,000 original miles. It had a camper in the bed for years and the last 10 years has only been driven twice a year. Always been in a garage. Which is good and bad.
Work done: 4 new tires, new brake fluid, carb rebuilt and replaced the base seal, replaced new defective front tank pump, new steel gas line from vapor separator to carb, oil was brand new, radiator fluid good, battery good, trans fluid good, spark plugs good, air filter good, gas filter good.

Problem: truck has been running good. I drive it to the train station and back home so I drive it about 5 miles everyday. Yesterday with it cold enough to snow when I went to drive home it wouldnt idle. I held the gas a few min and finally reved it up and it idled fine. On the way home the engine quit at a red light. Started back up but it seamed to not be getting enough gas when I let off the gas. Figured it was still cold. This morning it started up and I held the gas and was reving it up for 10 min and it wouldnt idle. If I let off the gas the engine would seem to slow down and cough and eventually die. I tried switching to the front tank but got the same reaction. I dont know if this truck has ever been driven in the winter. My first thoughts are air flow into the carb or out of the engine or fuel delivery? Im going to work but I was hoping for a few things to check tonight or this weekend. Please let me know if I missed any valuable information?

Sorry for the long post. Just wanted to give as much info as I could. Thanks in advance.

 

You say the carburetor was rebuilt? I'm betting the choke needs to be adjusted....

 

Yes. The guy even had the papers showing it had. I had just read on my commute that the choke is like the number one issue to a carbureted engine not wanting to idle in the winter. I have never adjusted an automatic choke only a manual choke. Is there a recent thread or pics? I can also search tonight.

 

I think there's some stuff in the Sticky/subforums at the top of this forum....

 

Is the air cleaner original? Does it have the hose going from the intake snorkel to the exhaust manifold? Just thinking that you may be experiencing carburetor icing.

 

I think it is original. I will have to double check. I will have to see if that hose is there and connected tonight.

Now not to over complicate but would the choke not being adjusted properly explain the issue I had last night with it idling fine and then dieing at the red light?

 

My experience has been that it is not uncommon to need to adjust the choke with each season, so yes, with the recent change to cold weather, the choke can be out of adjustment. It is not difficult once you do it the 1st time.

This link is to a thread of how to adjust a choke. It is written about a 1 barrel carburetor for a six cylinder, but the concept is the same.

https://www.ford-trucks.com/forums/1...ent-101-a.html

 

That sounds like a symptom of carburetor icing.

The original thermostatic air cleaner will have an enclosed air filter with a snorkel one one side. Attached to the front of the snorkel should be accordion tubing that attaches to the radiator support. That is where the cold air comes from. Attached to the bottom of your air cleaner snorkel should be round tubing that connects to a shield on the the exhaust manifold. That is where warm air comes from. There is a temperature modulator in the inside of the stock air cleaner base that operates a flapper valve in the snorkel that can actually regulate the temperature of the air coming into your carburetor. The system works off of manifold vacuum. When it's working correctly, your carburetor will receive warmer air when the temperatures are low, and cooler air when the temperatures are warm. This is better for driveability, fuel economy, and emissions.

If you have a fancy chrome aftermarket open-element air cleaner, you will receive NONE of these benefits.

If the bottom tube is missing from under the snorkel, the cold air coming in to the carburetor will actually get colder as it enters the venturi, which can cause carburetor icing if it gets too cold. When that happens, your truck will run rough and/or stall.

Capiche?

 

I just spent my lunch hour reading about carburetors. Lol

Im pretty positive its stock. I dont remember seeing an after market one on there. I will check tonight and make sure all the hoses are hooked up. With it recently being worked on you never know what didnt get put back correctly.

Thanks for the replys.

 

Ok. On sunday morning after the truck has sat for a couple of days I went out and removed the air cover. The carb was open I touched the flap and it closed. I pushed in the gas pedal once and let it out. Got out and checked and the flap was still closed. I turned the key and it started right up and idled. So I waited a min and pushed the gas pedal in. The engine reved up and the rpms dropped and it died. Turned the key and started back up. I let it run a few min then I was able to rev the engine and put it in drive and reverse with no issue. Now the interesting part. I go in for about an hour come back out and do the same exact thing. The truck now just cranks and wont start. I tried on both gas tanks.

This reminded me of something that happened before Halloween. The truck had been sitting all day. I drove it a couple of miles to dinner. A couple hours later we go to leave and it wouldnt start. Same thing. I finally put the gas pedal to the floor and it started and drove home fine. I thought something got stuck in the fuel line and needed forced out.

My father in law also told me this weekend that I didnt know. The shop replaced the vapor separator with a simlar after market one. Dont know if that matters or not.

I have to look up the carb and choke. So I know how to adjust it. This truck has more metal and rubber tubing then I have ever seem on one of these trucks. I got so many things sticking up everywhere I dont know what any of it is.

I agree that the cold start is the choke setting but the sitting for an hour or so and not starting has me worried.

 

Still sounds choke-related, possibly the choke coming (all the way) on when it really isn't needed at all and so it's being fed too much gas and too little air... that is my first thought.

Post some pictures and we can probably help you identify and understand what all that stuff is....

 

If your 1985 4180 carb is the same as my 1987, you might have an anti-tamper choke. If so, Originally the choke spring cover was held on with blind screws, so if it has slotted screws now, somebody has gone through it. But even if it has slotted screws you still can't adjust the choke because the spring cover is notched in such a way as to preventing you from rotating it. You have to remove the cover and grind off the notch to defeat this.

But before you tear into any of that, the fact that your choke closes when it is cold suggests that it is working, and the fact that you found the choke open when you took the air cleaner off suggests that it opens when it is running. The only question is when is it opening? It should be gradual, as your truck warms up.

The other vital component of the choke system is the plastic high idle cam, the purpose of which is to increase the idle speed when the truck is cold. For example, On a cold day my truck will idle at 1,500 on initial start up and then around 1,000 for a few miles until it's warmed up. Then it is 850.

So, if your choke is closed but your idle speed isn't stepped up you have a problem with your fast idle cam. Usually what happens is the arm with the tiny adjusting screw get broken off because someone was foolish enough to try and turn it! *snap* and the tension spring needs that arm to tension the fast idle system.

 

About your restart issues. Don't know how much experience you have driving a carb but it's an art. Like hitting a golf ball perhaps.

Unlike fuel injection, The thing to remember with a carb is that every time you wiggle the gas pedal the accelerator pump squirts gas into the engine. Therefore they are easy to flood.

Most of the time, if I've only been sitting an hour or two, I'm usually better off not touching the throttle when I hit the key. It usually fires right off and I'll lightly tap the throttle then for a crisp start. Hole in one! But sometimes I still bogey.

Also, a five mile commute to the train station isn't enough time to even remotely warm up a big block 460 in the winter. Figure a minimum 20 miles for that and you really need to get it up to temp often or condensation will form in your crankcase. Plus how can you expect it to idle when it's all carboned up from running cold all the time?

 

Yes. It is a 4180 carb and I see no way to adjust the choke. This morning I pushed in the gas once and it started up. Let it run about 10 min and it idled down without dieing. My father in law is going to start it throughout the day and see what it does.

I dont have much experience with these trucks. I learn from reading and working on them. My dad bought an 85 brand new when I was born. So I grew up in one of these trucks. This is the first 460 I have driven on a daily basis. I have been wandering with what I have been reading that my ignorance is the biggest issue. I was told from somewhere to always pump the gas 3 times before starting. I just read the other day to only do it once. New info to me.

I think I understand the the cold start procedure now. It makes since. Now I need to figure out the warm start issue. My father in law is going to test today. I read another post on here that a warm start issue could be a bad ground. My cables do appear to be 30 years old and the negative was laying agaist the exhaust manifold. My first f150 years ago. The exhaust manifold ate half way through my negative cable and was causing my battery to drain.

Since you have the same engine and carb any advise you can give me would be appreciated. Im not afraid to learn. Im already feeling a little bumb posting on here that I dont know how to start my truck properly. Lol

 

How many times the pedal needs to be pumped depends on so many different factors, there is no single "correct recipe" for all engines in all configurations & states of tune in all temperatures & humidity... you will learn how your engine likes to be treated and will act appropriately (I hope).