Started my 76 f150 with the 390 today. It was idling rough then died. It took a little to start back up and wouldnt idle without giving it gas. I started driving and if i kept it in a higher rpm it would drive okay but a little rough sputtering a little. If i shifted to 3rd it would sputter jerk and not really go. my first instinct was fuel pump so I replaced it. After trying and trying to start it still wouldnt start. I checked for spark and it is getting a spark. it is for sure getting gas. Where do i go next. is it carburetor problems. Im lost.

 

How often does the truck get run? Every week, every six months? Have to ask these questions to eliminate the obvious.

When you say it has spark does it have good spark - fat and blue and snaps in the air? Or weak and orange?

Is this a high mileage engine, what is the history - recent rebuild, etc.

First thing, not trying to pick on you, but help others who will read this - with an engine that won't start, always put the battery on a charger. Marathon cranking just wipes them out. Take it easy on the starter too, they will get smoked after a few start attempts. Give it several minutes rest between cranks. A well tuned motor lights off instantly.

 

Truck is driven daily. Rebuild in the last 5k miles. Spark is weak and orange.

 

That might be a problem, a weak spark in the open air means the plugs may not be able to fire at all, under compression.

 

Any Idea on what my next step should be?

 

That truck is a little too new for me, but basically you need to find out why the spark is weak, assuming this is the issue.

Probably some fancy module or other gee-gaw. BUT, one thing that I've learned is that anything electrical needs good grounds and connections, and unless you've already made some real effort in those areas everything will be corroded badly on a 1976 rig. An invisible layer of crud is enough to make connections fail.

start here: http://www.aa1car.com/ignition.htm

 

Where were you checking the spark? Where the coil wire went in to the distributor or at the plugs?

If I remember correctly, those engines had a separate coil, (not mounted on distributor) and would go out fairly regularly..I would be inclined to think with a weak spark, the coil would be the culprit.

 

so today I replaced the spark plug wires cap and rotor and my plugs. the engine was flooded and the old plugs were drenched. after replacing the plugs it started up but still ran rough. the spark is good. when pushing hard on the pedal it would stutter pop sometimes. seems like it was starving for fuel. i let it idle for a little then tried to drive. once i started driving it went right back to square one. It seems like its starving for fuel. it would barely run. it died a few times. id start it back up then it died the third time and would not start back up. After cranking and cranking it still wouldnt start. Im am starting to think carb rebuild. It doesnt seem like its getting enough fuel.

 

If the plugs are drenched as you mentioned it's getting plenty of fuel.

 

could it be getting too much fuel and that is whats causing it to not run properly. Is that carb problems?

 

are you electronic ignition or points

 

It is points

 

Points? In '76? May be, but I thought those were done by '74 or '75.

"After cranking and cranking it still won't start." Be careful, you'll roast the starter, and this may cause other problems.

Here is a direct link to a comprehensive "won't start" troubleshooting page. What have you determined so far? You have a voltmeter, right? Nod your head "Yes."

http://www.aa1car.com/library/us1296.htm

 

you say you have points have you replaced the points and condenser.the points should be gapped at 0.17 and dont forget to use the grease . id buy 2 sets throw the 2nd set in the glove box along with a flat head screw driver,feeler guages, a pair of pliers,and flashlight

 

Today i solved my problem. after figuring out we had a very weak spark, I was recommended an HEI Distributer and there was one at a local shop. It gets rid of all my point and condenser nonsense so I thought I might as well go for it. It was 150$ and I am very happy I did it. After installing it with some new HEI plug wires it fired right up. After timing it runs like a dream. It starts up very quickly and there is a significant performance upgrade. The engine runs so much smoother now. I Highly recommend it to anyone interested. I still need to clean up the wires and get a riser for the air filter or a smaller air filter. If anyone knows of an easy solution please let me know. Any questions about the install feel free to ask.