I have a 78 F150 4x4, and the other day I ran it out of gas or so I think. After pushing it home I left it sit for a day and then poured gas out of a can into it, primed the carb and hit the key.
It started right up and so I hooked it in gear and it stalled, so I thought, Well.... it's just cold so I started it back up and feathered the gas and hooked it in gas and it stalled again.
After multiple trys I finally got it to move in low range with the hubs kicked out.
When I would rev the truck up it would start popping and missing and just plain running like crap, It would even shut down on some occasions, I wasn't able to get it up over 25mph.
When I revved the motor in neutral and let off it would blow blue smoke (not while it was revving only as it was idling down from the rev.
In order to make a long story shorter,I will skip to what I have done to try to fix this problem:
Different wires, cap, rotor, plugs, I changed the carb,Switched distributors, changed the timing, put a different ignition modulator on it and put premium gas in the empty front tank.

Everything has seemed to make it slightly better but still is no where close to being drivable. It seems that if I shut the truck off for 5 seconds and start it back up, the truck will act just fine, but when you accelerate it starts screwing up again, right about when the truck winds out in second gear.
Here is a list of things that I thought about trying and haven't yet:
fuel pump, coil, look for a hole in the gas line where it might be sucking air??.

Anyhow, this thing has really got me down cause I always brag the ford up and now my mopar buddy is ragging on me pretty bad.

PLEASE HELP! Thanks so much for anyone who responds to this.

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When you say you changed the timing, -was it off very far?

You have not specified which engine you have.

How many miles are on the engine?

 

The timing in therory should of been dead on, the only reason I changed it was cause it was one of those last resorts that I thought I might get lucking by just fiddling with it, however it did nothing. The engine in the truck is a 351M, the odometer in the truck that the motor came out of read 80 some thousand miles, when I transplanted the motor I put bottom end bearings in it and, right after doing so, the motor locked up on me, then freed up and I have put over 3000 miles on it since with no trouble till now. Note: I found that if I take it extremely easy by barely pushing on the gas the truck will run without popping or missing, but about 5 seconds after I push the gas down just far enough to send it into passing gear it starts on it's spells. Sorry about not providing this info before hand, and thanks for the replies.

Adam

"Keep on Truckin"

 

I was thinking that if the timing was way off you might have slipped a tooth on the timing chain.

The blue smoke on deceleration or backing off the throttle comes from worn valve guides or bad valve seals. Usually some new seals will fix that one. The seals get old, hard, and crack.

>fuel pump, coil, look for a hole in the gas line where it might be sucking air??

Fuel delivery may be a problem, check the fuel pressure and volume. The tank could have a bad vent. The tank inlet could be clogged. The gas line may be sucking air as you mentioned.

The coil may be bad. Take ignition parts to the parts store. Ign modules and components can usually be tested for free.

 

I don tknow if this will help or not but... here goes,
I did the same thing not to long ago...i ran it dry.
Filled it up, it would run for a few secs then choke. I got new fuel pump. Seemed to fix the problem..temporarily. Then i was driving down the road in 2nd and it choked out on me out of knowwhere. Waited 2mins then fired up like nothin happend. As well mine would pop like you describe too. I checked the fuel filter, the one that screws into my carb, she was clogged to tha nines. So i replaced both filters....ever since no problems.
My 0.02$

 

Thanks for the replies guys. I took the fuel filter that comes out of the carb, and I blew it out with compressed air, but it didn't seem to make a difference. Is there another filter somewhere else on the truck? Can a fuel pump go weak? All I have ever seen Is one that worked or didn't. Oh and when I switched the dist. the truck was running excellent in the driveway in neutral, I revved the motor numerous times and not one sign of what was happening previous to that, but when I took it out on the road and got it up to about 50mph in 2nd gear it started missing and popping again. Thanks again guys!

 

Ok I had a simular prob long ago. My fuel pump just wasn't putting out the pressure my carb needed. Low pressure will effect performance and fuel starvation going into higher gears as your engine will require more fuel. Check specs for your engine on volume testing. Hope this helps. Nothing worse than a minor problem you can't find.

 

Ok so I tried changing the fuel pump right? and no go there. So then I went and got a different fuel filter, thinking the one I tried to clean might not of worked, well that didn't help. So after I messed and messed along side the road about a mile from my house walking back and forth with tools and parts I ended up trying a old 5 quart oil jug filled with gas and feeding the fuel line into it and voila! It ran like a champ. So I go home and pull the little side cover off of the front gas tank and inspect the fuel line by blocking off the end that goes to the fuel pump and blowing compressed gas through the gas tank end. and I came up with no leaks or air holes. So I unplugged the end towards the fuel pump and blew throught the line, the only thing that I could tell that came out was the remaining gas in the line. Anyways I hook everything back up and start the truck and all is good, but I figure well that is just cause it is running on what was left in the carb from the jug. Not so, it ran fine into town and back but this morning when I need my truck to haul a entertainment center it goes about 1/8 of a mile and starts sputtering, and coughing. So I turned around and took my dad's 78 F150 Trailer Special. When I get back, I figured I'd take my truck for a ride and see what it does. Well it ran alot better thatn what it did but still coughs every now and then which leaves me not trusting it. Any more Ideas? What about the switching unit that switches between the two tanks? I do have gas in both tanks. Thanks for the replies.

 

Something floating around in the fuel tank plugging up the fuel inlet line?
Do you still have the sock on the end of the inlet?
Just a thought.

 

Sounds like you might have some crud in the gas tank that gets sucked up against the fuel line inlet filter (sock) or that sock has gotten plugged up or collapsed. Sometimes when you blow air thru the gas line into the tank, it will blow the sock off the end of the line, which really isn't all that big a deal. My preference is to not have the sock on there, but I always install an inline fuel filter between tank and fuel pump - that way the car and the pump are protected. Unfortunately, the only way to really know is to drop the fuel tank and pull the sender unit to have a look inside.

You said that you blew out the filter with air, but in many cases, that doesn't do much, depending on the filter. Is it the sintered bronze type element or a paper type? If it's the paper type element, better to replace it.

Also, check the internal wiring inside the distributor - you may have a break inside the insulation or poor connection. See if the wires are brittle or cracked - they should be in decent shape and fairly flexible.

What type of carb do you have? You may need to replace the accelerator pump in the carb. With the engine off look down the throttle bores while pulling the throttle lever as if you were inside pushing on the gas pedal - you should see a good stream of gas squirt onto the throttle blades. If not, the accelerator pump is shot. If it's a Holley carb, a good backfire can destroy the power valve, which will cause it to run rich and rough.

Pinhole leaks in fuel lines are hard to find too - in that case the only way to know for sure is to install a new fuel line, but I don't think that you're at that point yet.

I'm also wondering about what you said about the engine locking up, then running OK again and if what's going on now may in some way be related.

Just some ideas good luck

 

Well I've concluded that the problem is in the rear tank, and I'm pretty sure that it is dirt cause if i run the truck on the rear tank it will go about 10 miles and then start it's habits. And if you clean the fuel filter out with the blow gun and air compressor the problem clears up so I've switched to running on the front tank and have had no problems what so ever and it doesn't look like I'm going to. So now it is just a matter of time until I find the time to drop the rear tank and fix the problem the right way. And thanks everyone who responded. I really appreciate it.

"Keep on truckin, cause if it breaks it needed to be fixed in the first place"