1977 F-150, 351M stock, Electric Ignition, 2150 carb

Truck was out of use for 4 months when I was out of state, when I returned my family said it didn't work even though they never drove it. (??) Anyways, first thing was the starter solenoid was melted, I don't think that has anything to do with my problem but thought I'd throw it in anyways since I don't know what my problem is, solenoid was replaced.

Ok, Truck starts up fine, idles fine, revs almost perfect (sometimes it hesitates with timing set to specs), when it's in drive it idle/drives fine but as soon as I go to give it gas it hesitates. It's not a normal hesitate though, it doesn't actually stall, more like the engine just sits there and waits for me to let up on the gas then it sounds fine, but I can't give it gas. Occasionally I can floor it and it will sound like the truck stalled for 2-3 secs (can't hear the engine) then it will accel ok (not how much power there should be), but if I stop accelerating it will psuedo stall again.

First thing I did was adjust the carb by ear, limped it ~7 miles then hooked up a tach and adjusted it again. Didn't help, although like I said when it's not under load it sounds nice. Put a new coil in thinking maybe they old one was overheating or not putting out enough spark. New motorcraft plugs, tried gaps from .40-.50, .50 seemed best. Played with the timing both ways. Also tried with/without vacuum advance. Replaced both fuel filters (at carb/inline) when changing the inline filter noticed some improvement so of course thought a new fuel pump would help, it didn't. Accelerator pump looks like it's putting out a decent amount of fuel. Tapped around the carb with a rubber mallet hoping it might jar something that was stuck. Right now I'm pretty stumped, I've been working on it a little a day for over a week now and feel totally clueless. I don't want to buy a new carb/rebuilt this one, unless I'm sure it's the carb.

Just cause I'm curious and don't know, electric ignition (non-points) have a resistor wire? I think my manual says it runs into the cab up to the ignition? What would be the symptoms if this was to go bad? And if it was bad could I just hook up a generic .8 ohm resistor to the original wire, or would it be better to run new wire.

Anyways, that's about it, thanks for taking the time to read this, if you have any suggestions, thoughts, or long shots please let me know.

Thanks,
-Mark

 

Added resistor, dropped voltage from (+) side of coil from ~11v to ~8.5v. Don't think it did much, most likely going to pick up a rebuilt kit for the carb tomorrow night, still looking for suggestions.

 

Check the compression.

 

I don't have a compression tester (yeah, I know, unbelievable, but never needed one). But I don't think it's the compression. First the engine has less than 80,000 on it and second I doubt ALL the cylinders lost compression from sitting for a couple of months. It was running fine before I left it, and I don't think it would run this bad even if two cylinders didn't have compression. I might go buy one anyways that way at least I'll have one, and of course if you are right and I'm completely wrong, well... :-)

Anyways, thanks for actually taking the time to read and reply. Right now I'm thinking the carb, maybe during the time it was sitting, had some deposit or corrosion build up on the inside(?)

Also I just remembered it developed a leak on the windshield gasket driver's side lower corner, flowing down drivers side dash. I don't know of any wires/connectors that would cause this, but if someone else does...

 

Maybe one of the carb orfices is plugged. Try some good carb cleaner down the carb while it's running and through the fuel inlet and ports. Sometimes the pressure can clean out things that you wouldn't notice. -if you haven't already.

 

sounds like the same symptoms mine had 3 weeks ago. Have you checked for proper operation of your choke? that's what blew on mine. it would start up and idle fine, and when put in gear it would roll, but when I tried to give it gas it would sputter and die. My carb was rebuilt at least once, so I just bought a stock rebuilt from my local auto parts store. Running much better now.

 

Stupidly enough, I haven't. I'll try that first thing in the morning (It needs an exhaust and I don't want to **** off the neighbors). Thanks for the obvious idea. :-)

-Mark

(why would it rev fine, does it take that much more gas to go?)

 

Choke works fine for not being connected. :-)

It's an electric choke, was giving me problems, so I just warm my truck up before driving. Carb was adjusted at operating temp in case you were wondering. Thanks anyways.

 

This happened to my truck and it turned out someone put somthing in my gas and it was making it run horrible when i filled it up again it started running fine. It could be old gas
Anthony DiPietro
79 F150 Ranger

 

hmmm... That never even crossed my mind. Of course I would have gone and filled my tank right after coming back (gauge doesn't work and I thought maybe just running on fumes), so it probably has 8 gals or so of 'bad' gas, and 12 of new gas. Would 8:12/2:3 be enough new gas to cancel the bad?? Too bad it's impossble to siphon gas from me (kink in the hose and length), maybe I'll take out the sending unit (which, on a side note, does anyone know where I can get a new unit, all the ones I find for the 77 trucks are for in the cab tanks, mine is over the rear axle).

This morning I used up a couple cans of carb cleaner with no luck. Bought a carb rebuild kit and fuel pressure gauge. Fuel pressure is about 5.7 or so, should be six I believe, but I think that's close enough.

Do you think some water remover/octane boost would help with the bad gas?

Thanks for your help,
-Mark

 

sounds tome like a vaccume advance prob just what mine done
replaced the advance and its fine

Rodney
82 f100 3.8 3onthetree caught fire after i just rebuilt the engine painted it and all up in flames darn the luck
looking at a 69 f100 360 3on the treeect ect

 

 

Nope, checked that when I was playing with the timing, seems to be ok. This morning I started to drop the fuel tank to look for deposit/debris clogging the pick up screen. After taking off one strap decided the tank was a lil more heavy than I felt like dealing with, so siphoned five gallons out, which I will put in my car as soon as it's low on gas (I just filled it -- of course). So probably finish dropping the tank later this week. If the tank ends up being ok, I'll prolly start the carb rebuild. While the tanks out I'll probably decide to sand/paint it and the straps/replace all fuel lines, I just wish I could find a sending unit for it while it's out. All the universal units need a 2 1/4" hole, and I believe the tank is a 2" hole.

Thanks for the idea, all help is appreciated, I'm working in the fuel tank/carb direction but I'm not sure that's the problem, I hate to be a "replace parts till it's fixed" type of person, but right now that's where I'm at. :-/

-mark