Hey All,

I have had my 72 f100 for about 3 years now and ever since I got it I have always had problems during the winter when warming up. It will start and idle fine but no matter what I do whether leave it at idle or kick up the rpms it dies and will not get restarted for the life of me. It acts flooded but when I try to start it how you should when it is flooded it almost never works. I have rebuilt the carb, replaced the fuel pump and filter and it still does this when it is less than 50 degrees out. I am stumped so any suggestions would be very helpful.

Thanks!

Ps engine is a 360 with a 2 barrel motorcraft carb

 

Could be weak spark.

 

How is the choke working?

 

Auto chokes you either love it or hate it. Many people switch it over to a electric chokes to make it some what better drivability. Check choke butterfly for being closed to tight.

Me, I'll take a manual choke.

Orich

 

Not sure how the choke is set up. I know it's mostly closed when starts and then once it is warm it is fully open. I've heard zip-tying it open during cold weather helps? Could just be a myth. What do you guys think

 

Yes it's a myth. You might try zip-tying it almost closed until it fully warms up.

 

I too fall victim to this. I ended up flooding it this morning as a matter of fact. I don't believe my heat choke is working well. Thinking the spring is worn out. because it doesn't reset correctly when you depress the gas....can anyone tell me what the small 1/4 hex head screw right of the heat choke **** does? Seems like all the way down causes the heat choke to function better.

Heres a question for the brains on here: what is the science between the thinner cold air not running through the carb as well? Why does warm air work better or a choked off air supply?

 

An engine needs a much richer mixture when it's cold. It's not thinner it just takes more fuel, as opposed to air, to run when cold.

 

The choke doesn't work in exactly the way one might think, it does reduce the airflow, but what it also does is increase the velocity of the air through the venturi, and this "sucks" more fuel into the airstream out of the well. In a cold engine what happens is the atomised fuel sticks to the sides of the intake runners instead of being vaporised, so more (richer) fuel mixture is required. It will warm up much quicker under load, so as soon as it is running smoothly, get underway (drive gently) in extreme cold with the choke on. If left idling it will take forever and load up the plugs, dilute the oil, etc. Manual chokes work great and are a lot less trouble than some versions, I agree.

 

Thanks for the choke explanation. That makes much more sense.

 

I agree check ignition, many "carb problems" are ignition related. Should be a fat bluish-white spark at a plug. Yellow or Reddish- Orange is no good.

These old trucks usually always have bad cables and ground connections unless a lot of attention has been paid to them, if they even look kinda old they should be replaced with #2 sized cable (or better) directly from battery to block or starter bolt, positive to solenoid, starter cable. Block to firewall and frame are important, but #4 size is OK. Grind down to bright shiny metal and tighten securely. Once they get old and connections corroded the voltage is reduced to everything, and the starter soaks up all the current at that instant the spark needs to be hottest.

When ignition (and ignition timing) is squared away for certain then go back in and setup the carb from scratch. Make sure there are no vacuum leaks, a vacuum gauge needs to be part of your tool kit, linkage is zeroed, butterflies open all the way, - float height and fuel height, accelerator pump, choke pulloff, idle and idle mixture settings carefully by the book.

 

I think that's a hillbilly fix and how is going to start cold with it tied open, except to pump the heck out of it, which washes down cylinders and dilutes the oil. When they are set right they work ok on most vehicles. Sadly the one on these trucks was engineered by a mental midget. They never worked very well in real cold weather even when they were new.
The choke should be firmly closed cold and break open a little when it starts, roughly 1/8 to 3/16 inch and then slowly open over the next minute or maybe a few minutes if real cold.
Do you get out and see if it's open or closed when it won't start? Just exactly when does it restart? Doesn't sound flooded, sounds like the choke needs adjusted. Could be a lot of things.
I'm with Oric on the manual choke, if it is a carb that was designed to be, not some hokey conversion. I hoarded 65-68 2100s for years just for that reason.

 

I haven't looked to see if it is open or closed when it dies but I assume it is still partially closed being that it isn't fully warmed up yet. I drove it the day of from two towns on the freeway going 70 about an hour and 45 minutes away. Got to my destination, let it sit at idle for about 5 minutes then shut it off. Came back outside about 4 hours later, started it up fine, idled fine until it just died idling. Tried to get it restarted and it just wouldn't budge and at this point my battery was about to die so I just said f*** it and would try again in the morning (I do this sometimes when it is truly flooded and didn't want to deal with it). Tried again in the morning and it still wouldn't start. Carb wasn't getting gas for some reason so I tried pouring some directly in and still wouldn't start. Finally I took a wrench and banged the fuel pump a couple times. Put in some gas in the carb and it started and idled fine. Hasn't had a problem since then I have started it again in normal temperature I.E. 60 degrees. Guess it was a fuel pump issue but does not make sense since I replaced the pump about 8 or so months ago.

 

Have you checked the condition of, or cleaned out the the fuel tank and the lines lately? Pin holes in the rubber lines cause all kinds of ghost problems.

 

Many times people forget about the rubber flex line joining the tank hard line to the frame hard line where it can crack an suck air causing a fuel starvation. Or a fuel leakage when parked.
Orich