Hello All, I've been a lurker here for quite awhile and finally registered great site by the way! I bought a 78 f150 with a 351M, motorcraft 2150 that I'm having some problems with. Ran terrible when I first got it so I cleaned out the entire fuel system, rebuilt the carb, put on a new fuel pump, and it fired right up ran awesome for a couple days. I was driving home one day and it started stumbling and backfired through the exhaust and blew out my muffler! Limped home and adjusted the carb a little took it to the dump and it sputtered a bit but made it, let it idle at the dump and ran perfect on the way home, went for another trip and ran terrible. I did some searching on here and figured I could have a timing/ignition problem so I replaced the distributor, cap, rotor, plugs, and wires and readjusted the carb, I also cleaned out the EGR plate and made sure I dont have any vaccum leaks. So my problem is it runs great at idle but sputters/stumbles and will not run above idle at all. I really need to get this truck running and I'm sure the answer is on here somewhere but if I could get a few suggestions I'd appreciate it. I'm not familiar with the 2150 at all and I'm sure thats where my problem lies. I appreciate your time.
Thanks,
Gary

 

I just rebuilt the 2100 on my '78 F250 400 last week after I bought it and stumbled it home.

Alot of things jump in my head as far as your problem goes but I would almost bet there is some crud in your main jets/venturis.

 

Just a couple of questions.How's the compression? Ignition advance? And do you still have any catalytic converters on it? The reason I ask is if you've rebuilt the carb maybe the problem is somewhere els. Good luck.

 

Check the carb for trash.

 

Have you put a fuel psi gauge on it ? Could be a problem in the line somewhere.