Ford 4.9 carb/choke issue

TeamSpatula

TeamSpatula

Well-Known Member
Joined
Jun 2, 2005
Location
Hickory
Good morning. My daily driver is an 81 F100 with the 4.9 I6, all stock. Lately it starts up fine, then after about 5 seconds runs rough until it warms up, when it's fine again. But, if I stop for 15-20 minutes, like at the grocery store, then it takes a minute or more of cranking to start up, during which I have to pretty much alternate between keeping it floored and pumping the pedal until it catches.
I thought maybe the choke was sticking, but when I pulled the air cleaner, I found the opposite. When I crank it up the choke is actually staying closed for a while, making it stumble. When I open the choke by hand the idle smooths right out. But the choke itself flaps freely, and it must be opening up with engine temperature, since it's fine when it warms up. With all the smog/emissions stuff on there I have no idea where to look, any leads? Thanks,
 
got 1 wire coming from it, so I assume one of those that the electricity heats up the element to open it once it's running? Also alternatively, since I know this is a pretty specialized issue, can anyone recommend any good ford truck forums? Thanks...
 
FTE covers pretty much everything. Fordification covers mostly 67-72 and Slick60's covers 61-66. There's a few bronco forums as well.

I typically know ford trucks well but I wouldn't want to lead you wrong on this one. My best guess to start might would be the choke? If it runs, it's not a fuel or spark issue. You can always just disconnect the choke and just have to warm it up before driving. If that works, replace the choke. Heat issues can either be carb or even heads or ring issues as well??? A compression check would narrow it down to either the carb or the motor. I've heard those carbs love rebuild kits but that don't sound like the issue either?
One last thing would be the fuel filter or gas tank. Crud in the gas system makes one run sometimes and then when the crud settles, it don't run until it gets stirred up again. THat would be the case to where it's getting fuel from the carb immediately to start the truck and nothing else comes through the system causing it to starve. A clear sight fuel filter usually tells the tale if you've got crud or not.

Hope that helps? FTE has a specific forum for the I-6's. There's also FordSixPerformance for I-6's specifically.
 
Thanks for the info, and probably a dumb question, but what is FTE? I tried fte.com and it's definitely not about Fords.
:)
I'm pretty sure it's a choke issue, but with all the smog stuff on there there are a few vacuum lines running to it, and I have no idea which is which...Once it's warmed up it runs fine...thanks,
 
Just a thought for diagnosing? You can unhook (and plug) all the vacuum lines except for the distributor advance vacuum line (if not mechanical in which most are vacuum from factory) and tranny modulator valve line (if it's an automatic tranny) and it should still run and drive. Then unhook auto choke and hook a cable to operate manually. Give it a shot manually and see? There should also be a copper line going from bottom of electric choke to intake manifold or exhaust header somewhere to detect heat. That's how it works. There's generic kits to redo it to the header being the most common. What could be happening is that rascal is burnt in two, it's common and happens over time.
Also, to diagnose a vacuum leak you spray starting fluid around everywhere except where it can go into the carb and if the engine revs, the vacuum is sucking in somewhere and you have a leak.

Sorry, Ford-Trucks.com. I think they changed domains sometime back? I recall it as FTE (Ford Truck Enthusiasts) back in the day? I only go there when I'm desperate. Nothing against them but I just rather start with people I know personally first. Smaller local forums like NC4x4.
 
I'm not real familiar with Fords but most carbs have vacuum choke pull off which partially opens choke when engine is running. This over rides the normal opening pattern . The choke pull off is vacuum operated (check hose) and is adjustable( sometimes by bending connecting linkage) There is a diaphram inside that could be leaking.
 
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