YFA Carb rebuild update

[brianbronc]

I have a 1986 F250 4x4, I6 300, gas truck.

My son (17) rebuilt the carb and got it reinstalled with new spark plugs. Won't start cold, have to use starter fluid. At first, no idle at all. Adjusted the idle screw and ran better. Especially after it gets warm. Idles at 1000 and runs good. Also, slight adjust to timing was done.

It sat for a couple hours and needed starter fluid to crank. Slight stumble at first, but skinny pedal helped keep it going. A couple revs and it stayed running.

What to look at 1st, 2nd, etc.

thanks

brian

 

[Gary Lewis]

I'm not a carb expert, but the fact that it runs after you get it started seems to say the carb is together correctly. But my guess is that the choke is not adjusted correctly, which can cause it to be hard to start. It should almost close when the engine is cold.

And the fact that it idles at 1000 RPM suggests you have a vacuum leak. Check your gaskets where the carb bolts to the manifold to ensure they are the correct ones. And that the bolts holding the carb on are snug. If that's ok then check vacuum hoses.

[Ford F834]

1986 should be a feedback carburetor… unless it was back converted to DS-II ignition. If it is feedback regulated, all the peripherals need to be in good working order. Also check for leaks at the PCV grommet. That can create hard starting and rough idle issues.

[FuzzFace2]

I'm not a carb expert, but the fact that it runs after you get it started seems to say the carb is together correctly. But my guess is that the choke is not adjusted correctly, which can cause it to be hard to start. It should almost close when the engine is cold.

And the fact that it idles at 1000 RPM suggests you have a vacuum leak. Check your gaskets where the carb bolts to the manifold to ensure they are the correct ones. And that the bolts holding the carb on are snug. If that's ok then check vacuum hoses.

Both are right on what they posted but ..........

The 1000 rpm at idle could be the speed screw needs adjusting.

First do we need to pass smog and if so do they look under the hood to see what is in place or not?

Do they check the tail pipe with a sniffer for gas levels?

If not then it might have been best to get a non-feed back carb off the bay but rebuilding that carb was a good start so your son knows how it is done back in the day.

When he was done and motor off looking down into the carb if the throttle is moved you should see a stream of fuel spray into the carb.

If not the accel pump is not working. There is a small plastic hose that needs to be hooked up just right in the bowl for this to work.

Yes make sure the choke is closed all but maybe 1/8".

Also how is he or you starting the truck? You start it differently than a EFI car or truck.

You need to pump the throttle at least 1 time to the floor and up.

This does 2 things, set the choke closed and gives a spray or fuel down carb to start.

Sometimes you may need to give it 2 pumps for more gas to spray before starting.

If the choke is adjusted right and closes it should pull on the fast idle cam and keep the idle up till the motor has a little heat in it. Fast idle needs to be adjusted (there is a fast idle screw) when cold and choke is on so you dont have a lot of time to get this done LOL

As the motor warms up the choke will open but till the throttle is moved the fast idle will stay on and the motor may race, just hit the throttle and it should come down to normal idle speed.

The motor now up to temp you can adjust the idle speed as needed, there is a screw for this too.

Now to start the motor when hot all that should need to be done is hit the key and it should fire up.

Now with todays fuel the gas in the carb bowl can boil and cause the motor to become flooded. If it will not start by just turning the key hold the throttle to the floor and crank till it starts.

Just a little lesson on how to start a motor that has a carb

Dave ----

ps we can walk you thru any of the carb adjustments just let us know.