So i just got my baby back and insured. I took her to a mechanic shop where a buddy works so we could drain and refill the rear axle. As i turned onto a main road it ran good until i got into the next turning lane. When i let up on the gas i noticed it was gonna stall, so i kept giving it gas to keep it running till i crossed the road, when i crossed it i let up completely and let her die on me while i coasted into a parking lot (phew).
Ok so heres some things to consider:
-1978 F150 4x4 300i6 (my baby) has been sitting for probably over 6 months
-I took it mudding the day before, ran fine
-very low on gas, current theory is that the gas went bad baisically
-After it died it would start up normally and idle smooth as usuall
-i took back roads all the way there, it wasnt until i had to give it some gas that it started acting up
-it runs good at idle, after given gas, when rpms start going down it goes all the way down till it dies, it dosnt try to run, it just dies
-if held at 1/4 throttle it will rev, start to die, rev, start to die and so on
-yes, i changed the fuel filter
-dont ever listen to people that work at a place like tire kingdom and think that theyre mechanics

 

sounds ignition realted. timing, or coil, or duraspark, or vac advance.

DT

 

Bad fuel pump? When you say 'after given gas', are you squirting gas into the carb, or just pumping the pedal a couple times?

I'd spray the crap out of the carb with carb cleaner! :P

 

check the accelerator(diaphram) pump linkage on the front of the carb. It may have popped loose. When this happened, this caused a starvation problem when turning corners on mine, which would kill the engine, but would restart just fine since it had already leveled out. Or the vacuum advance line popped off.

 

i mean when i take my foot off the gas pedal on the decel, like if i was to come up to a stop sign and take my foot off the gas, it would die by the time i got to the stop sign. Pumping the gas gets the same effect, if i give it gas it wont stall until the rpms come down, so i have to keep pumping the pedal if i dont want it to stall

 

im looking at it now, there seems to be some slop in the pedal. Could that be related?

 

I don't think pedal slop would be a problem with idle. If your carb is set up properly, that is.

What kind of carb do you have, and what condition is it in? You said it sat for six months, did you do anything to it after it sat - like clean it out, flush it with gas, rebuilt it ... anything?

If pumping the the pedal keeps it lit, but just pressing the pedal down slightly and holding that position does not, then I'd say that your pumping action is simply shooting gas in there by actuating the accellerator pump on the carb. If that's the only way that it's getting gas at idle, then it seems there could be a few problems.

One is that the idle circuit is clogged and when the primary is closed, there is no fuel getting through. (A good hosing with carb cleaner should fix that)

Or...your idle screw is set way too high and the primary isn't closing as much as it should, effectively starving the engine of fuel.

But then again, if your carb is in bad shape, you could be sucking air from any number of spots where a gasket or seal is bad.

So, tell us what kind of carb you're using and when was the last time it had some attention?

 

It is the stock carter single barrel. What condition is it in? Well I never messed with it to be honest, and this is the first time its ever given me a problem. I didnt do anything to the motor when the truck was sitting. I would occasionally fire it up and take it around the block, but i did that about once a month. Im typing this just as i came back from messing with it. The truck actually started and ran fine! I am really confused at this point cause i didnt do anything. All i did was take off the air filter, look at the carb to make sure hoses are in place and nothings leaking. Sure enough it started right up and ran fine. I put the air filter back on and it started again and ran fine. I got class (auto repair class) in like an hour and ill ask my instructor and see what he thinks. oh yeah also when you say hosing with carb cleaner, i assume you mean to spray it straight in the carb right?

 

tap the top of the carb w/the handle of a decent size screwdriver(dont use a hammer, you'll bend/crack the carb)......I'm willing to bet the float's sticking a lil bit, it happens when they sit a while.

 

Have you dropped the gas tank? Could have rust or crap in the tank blocking the pickup screen. Drive it...crap gets stuck engine dies. Engine stops and crap goes back down to the bottom...so on and so on. Good luck!

 

Yes, start the truck and shoot carb cleaner in the throat of the carb to help clean out the gunk from the idle circuit. The old 1 barrels had a tube sticking out at the top of the throat that opens upward. That should be a vent tube to the bowl, you might put a little carb cleaner in there too, just to break up any goo that may have formed from the gas sitting in there a while. You might have to goose the gas while spraying carb cleaner in there to keep it running, but that way it will burn the carb cleaner out instead of just accumulating in your manifold.

If you spray carb cleaner in there without the motor running, it will be hard to start!

But then again, if it's working fine now, LEAVE IT ALONE!