Recently acquired a 1980 f100 custom 4.9 300 with Carter yfa non feedback carb. Has 55000 original miles. Nice looking truck. Sat in garage for a while and when I got it, it would crank right up. Really rough idle, would flood itself out. Decided to rebuild Carter yfa carb and now cannot get it started. Sometimes backfires through carb when cranking.

 

Welcome to FTE
Did you drain all the old gas before you tried to start the truck even before the carb rebuild?
If it was flooding over, stuck float needle, I think I would throw a new set of plugs in it as they could be fouled and keep it from starting.


That is were I would start, plugs, and report back if it still does not start.
Dave ----

 

Anything I bring home that has not been driven in 6 months gets the whole fuel system cleaned good, including the tank and all the rubber hose and stuff replaced.

 

 

Is it still pouring fuel down into the engine? It won't fire at all if it's still flooding out.

If it's not flooding out, then take a small cup of fuel and pour just a little bit down the carb throat and see if it will try and sputter. If it does sputter, then you have gone the other way and have no fuel at all. I would check the fuel pump, you can put a hose on it and put it in a bucket, and it should squirt strong streams of fuel in the bucket when you crank it over.

Like one of the previous posters said, you are going to fight this thing for awhile, even in a couple of months the newer ethanol fuel they sell now goes bad. If you get it running and plan on this being an extra vehicle so it will still sit alot, you are better off to find a station around your area that sells fuel with no ethanol, and use it in the truck. If you are near the water, you usually can find non-ethanol fuel that they use in boats,, they have the same problem.

 

I have been hoping the PO wasn’t using ethanol gas as I’m in iowa and it’s pretty much taken over, but I can still get good ol’ straight unleaded fuel it just costs more. I’m pretty sure it’s still getting enough gas, you can smell it really strong when trying to crank. I Looked down into the top of carb yesterday and it did seem dry I’m not sure how much fuel I’m actually supposed to see in the bowl... you can see very small stream shoot in while ignition on and throttle is hit. I’ll check the fuel line today and make sure I’ve got plenty of gas to carb

 

If you see a small stream when you hit the gas pedal, then you have fuel. That is all the fuel you should see when looking down in the carb. If you see any other fuel dripping inside the carb, then you re still flooding it out. Take the plastic end of a screwdriver and while someone is cranking the engine, rap the top of the carb with the screwdriver and see if you can knock the dirt loose under the float needle.

 

 

I would say 6 months it could be turning bad and if you added that gas 6 months ago on top of older gas it is bad.
Year old I would say its bad.


You said it back fires thru the carb. Did you have any of the plug wires off? If so all off at the same time?
If so check the firing order as you could have a wire crossed.
Dave ----

 

It will run on the fuel, even if it's old. The problem is the fuel turns into a sticky goo and then that breaks loose and clogs everything up when you start messing with it.

When that truck sat for a long time, the ethanol fuel sat in the carb and turned into a sticky mess and dried up. When you add new fuel to it, everything is stuck and clogged up with this old fuel. It also tends to ruin rubber parts of the fuel system, I would not be surprised if sometime in the near future you have to change the fuel pump.

Take a peek down the carb while you are cranking it, or right after, if you see fuel all over the place, your float needle is hung up with goo or it has a piece of dirt under it. It works just like a toilet, with a bowl, and a float with a valve. If that thing is stuck, the bowl will overflow into the engine and flood it out. You may be able to get it running if you floor the pedal and give it lots of air to try and clear it out. Pecking on the top of the carb helps most of the time to get stuff unstuck.

 

 

Being an 80 you don't need a lot of vacuum lines for it to run.
If you have power brakes you need a vacuum line for it.
Next would be a vacuum line from carb (ported side) to the dist. for vacuum advance.
The last and could be a LARGE leak is the PCV.
(all of the above could be plugged to get it running if you want)
Anything else is not really needed for it to start/run/drive but there are some others that might be needed.


With that said plug off all other ports. There is a vacuum tree at the back of the intake manifold and the caps dry and crack causing a leak.
You can also look up on Youtube checking for vacuum leaks using somke that can help you find any vacuum leaks.


To make sure you are using fresh gas, disconnect the line to the fuel pump and get a small gas can with fresh fuel. Use a long rubber hose to go from pump to the can. Don't forget the carb has old fuel in it you will have to get rid of before it gets fresh gas.
Dave ----


BTW my 81 only has 2 more vacuum lines, 1 for the AC and the other for the air filter assy.

 

 

In that case plugging them all just to get it running would be ok then once running hook 1 up at a time to see if that is a cause why it will not start.
Dave ----

 

Firing order is correct, yes? Static timing is good, yes? Cranks over fine, yes?

Good spark (fire) from the coil wire to ground? Good spark (fire) at the plug wire terminals to ground?

Clean battery terminals and posts are a must...along with the solenoid's terminals and ground. Make sure the solenoid is grounded to a clean piece of firewall (?) metal.

You have gas you said....and no more "flooding" problems, correct? You have air - as witnessed by a backfire through the carb....and some "fire" as witnessed by the same backfire....

BUT! Backfiring is an indication of a timing issue, crossed plug wires and a somewhat "lean" condition.....or all of what was mentioned.

Have you addressed the issues Franklin 2 mentioned in post #7 and #10?

Bad gas won't stop the engine from running, but she'll run like poopies and will have to be kept at a high idle......
A vacuum leak won't stop the engine from running but if you have a boatload of leaks, well, that's asking for trouble in starting. I can't imagine every vacuum line is shot, though. Good idea on checking them all including the vacuum advance can's diaphragm. There's a somewhat large leak going into the ported nipple on the carb.

FuzzFace2's posts #12 and #14 have merit.....