Hi guys!

I apologize if this post is repetitive, but me and this "search" function don't get along so well.

I've got a 77 F150 4x4. 351; 2 barrel carb; 4 speed manual tranny.

I drive it on a fairly regular basis. But it has sat for the last month. The other day I jumped in to take it for a spin. It cranked and cranked and cranked like there was no fuel. I pumped and pumped and pumped til it started. It has done it like twice again. But usually starts normally. This morning, I took it to work. Been driving for about 10 minutes, and it died. I'm coasting in gear for just a few seconds and it fires back up and backfires very loud out the exhaust. Almost to work, I cruise on in.

Coming home, same thing. About 10 minutes into the trip, it does the same thing. This time it blows out my muffler. Now I sound like i"m driving an old farm truck. Then it did it to me one more time, cept I stepped on the clutch and pulled over. Then it cranked and it cranked and it cranked til it fired back up and I went home.

What do you think? Fuel or electric? I can fix stuff, but not so great at diagnosing. Obviously had SOME fuel to backfire that hard, right? Am I losing spark for a few seconds then gaining it back again?

I'd appreciate some thoughts if you all have any. Holler back if I can give more explanation. Thanks!!

Scott

 

Most likely electrical. When you allowed the engine to turn without spark, you had fuel going into the exhaust. Once it fired up, that unburned fuel went off. (boom). I would start with the ignition switch and go forward.

 

Fuel
A stuck float can act this way .. Loading up with fuel
A worn or dirty needle and seat can act this way .. creating an overly rich scenario
Retarded timing will act this way because it's not burning all the fuel in the cylinders

Electric
Intermittent spark can leave unburned fuel

 

Something is shutting off the ignition. If I had to take a guess, I'd say it is the pickup coil in the distributor, ignition coil, or the control box for the ignition on the inner fender. There are ways to test the pickup coil, tests have to be done when the engine won't start. Check all the connectors at the ignition switch, distributor, starter solenoid, & ignition module. Make sure they are clean & tight.

The engine keeps spinning, pulling gas & air into the cylinders, then pumping it into the exhaust. When it starts firing again, the fuel air mixture ignites & explodes.

Back in my younger days, we used to do muffler explosions all the time. Cruise along at 35 or so, turn the key off one click for a few seconds, turn it back on. BOOM!!!! Great fun when a dog was chasing you! I had a 76 F150 4WD with a single 3" exhaust pipe straight out the back. Late one night some dullard was tailgating me. I lit off a big muffler explosion, it looked like a ball of fire rolled over his hood. He backed off right quick!! Glasspacks were the best, they were very hard to blow apart. Rusty mufflers usually came apart in a couple of explosions. AHHHH, the fun of vehicle abuse!

 

Thanks guys! I might add that.....when it dies, it does so cold turkey! No coughing and sputtering, just dead!

 

Sure sounds like an ignition issue if that is the case.

I know you say that you cannot diagnose a problem, but ummm.... you are going to have to in this case.
At the very least you'll need to run through a few systems to figure out where the fault lays.

good luck!

 

Cold turkey! Sounds electrical to me. I would start with the coil connector. I've seen countless coil connectors with frayed wiring where the wires go into the spade terminals.

 

Keep in mind, when it's required to "crank and crank and crank" this will smoke the battery, and hard. They are not designed for that and will be ruined quickly if not charged up.

The alternator will be tasked to charge but they are not designed for that, and can be ruined by a defective battery. Especially, starters are not designed for marathon crank fests. It will get smoking hot, may not fail right now, but it will fail fairly quickly.

Not trying to beat up on you, but this is a textbook example of how a tiny fault causing a no-start condition in turn affects other major sections or components and can get pretty expensive and extensive if not remedied right away.

 

Sounds like an ignition problem to me also... as mentioned, easy to get a nice backfire and blow the muffler with a MT truck if the ignition fails briefly or is shut off then turned back on while rolling...

 

^ This is my first guess. If the mounting bracket is a little loose and it sometimes bounces out of position, it would kill the ignition, but could fall back into a good enough position to run after enough cranking sometimes. If when you're cranking and it's not starting, it fires once right when you turn the ignition off, that would be a confirming symptom of this.

 

Hi guys, I have not yet begun to work on this issue. Been busy. But I'm about ready. The other night, I came across this old thread. Related??


Do I need to buy a multimeter?

 

....oops.... https://www.ford-trucks.com/forums/8...-problems.html

 

What!?? Do we look like the kind of people who would tell you not to buy more tools? Sheesh! Ofcourse you should buy a multimeter.

 

Ditto, or the coil itself....


my brothers '63 chevy pickup would unload the condenser every time he shut the key off and the engine stopped rotating, blew his mufflers off multiple times and also made it hard for him to sneak home after curfew.


Not the you have a points or a condenser but figured I would bring it up...same principle.

 

ha ha....ok. I do have lots of tools. Just, my electrical skills are weak....... I will have to study on how to use the dang thing.....