Hey guys.

Disclaimer:I am not a mechanic, but i enjoy (mostly) working on my vehicles. I use Forums and YouTube as much as possible. When I can't find what I am looking for or if it is beyond my skill level then I'll take it in. Hoping not to take it in!

Background on the truck: I was gifted a 1976 F150 Ranger XLT, 6 cyl 3 on the tree from my father in law a few years ago as a project for my son and I to work on together. The things that need to be replaced right now aren't important...new window seals, interior upgrading, dash lights, etc.

My father in law replaced the carb, distributor/cap, plugs, wires, fuel filter and alternator. When I received the truck, it ran horrible. Anything over 25mph and it would hesitate and stutter. Forget trying to accelerate. It would bog down and you could gingerly coax it up to speed, but only about 40-45 mph. As I drove the truck home (freeway) it backfired twice and shut down. Flames came out of the tailpipe. I eventually got it home.

Within a few days of fiddling around with the timing, I managed to split the muffler in half. Sounded like a 12 guage. I replaced the carb and had a new muffler installed. Still ran like crap. I got underneath the truck and noticed that where the pipe sections connected with one another that they weren't bolted together with the clamps that were around the pipes. I installed bolts and the it made a tremendous difference. I could actually drive without all the "stuttering"...it still happened on occasion, but not often. I was also able to get up to 80 mph. Game changer.

I only drove the truck around town to do errands or when the kids had the other car. It did just fine. After a few months, I discovered that it would occasionally just shut off while driving. I can only remember this happening while on the freeway. Most of the time it happened as I was accelerating. I would just hear the engine "cut out" and I would cost to the shoulder. Usually it would just start right back up and I would be on my way. This would happen every couple of weeks.

Last week it happened again. It happened as I was thinking, "Boy the truck is running really well right now!". I was going up a hill and started to accelerate when it cut out. Pulled over to the shoulder and the engine cranks, but wouldn't "fire up". I attempted to start it up a few times over the next hour after letting it sit 10-15 minutes in case I had flooded it. Eventually I gave up and had it towed home.

Next morning I went out and it started right up. It was a little rough starting (it has never been super smooth, but pretty generally pretty good). Drove it out to the garden area on my property, did some work, went to move the truck...nope. Engine just turns, but doesn't fire up. Sat there for three days. On the fourth day I got lucky after several attempts. Got it back in the driveway. Started up on the 5th day, but didn't drive it. Hasn't started the past two days.

When I went out to try it an hour ago, no luck. What i did notice was that gas is leaking out of the carb. I only gave the truck the customary two pumps before turning the key. Usually that is all I have to do to get it to start. Not today.

So, that is where I am at. Any suggestions and advice would be greatly appreciated! I have included some photos that I hope will help. I included shot of the carb so that you can see where the gas is leaking.

 

I would check to make sure its firing out the plugs with a good spark , maybe coil is failing , check for vacuum leaks if all good then its most likely fuel related , you stated you replaced the carb , , were was the fuel leaking at carb ? maybe float is sticking

 

Have you ever checked to see if you had a spark from the coil wire? Try holding the distributor end of the coil wire about 1/2” from the engine when it does not want to start. You should have a blue spark at that time. I would not be surprised if the electronic ignition module is causing your problem. Also remove the distributor cap and make sure the reluctor wheel is not loose.

 

I had an issue recently where my manual choke was getting stuck and it would behave similar to how you describe. If I let it sit overnight, it would start the next day, but I would drive a few blocks and the choke being permanently engaged would choke the engine out and I would have to coast to the side of the road. Then when I would try to restart it, it would crank but not start. I had to take off the air cleaner and physically open the choke plate so that air could get into the carburetor.

 

Shuts off while driving: Overheated ignition module, a very common problem on 1974/79 FoMoCo vehicles with DuraSpark electronic ignition.

When the puppy cools down, the vehicle restarts, but sooner or later the module will overheat, BURN OUT. Now...it will not restart.

 

Thanks for the replies. I haven’t been able to work on the truck since
spring....wife had me out in the yard getting the garden ready 😀. I will try out the suggestions today if the rain stops. It’s currently out in the open.

in the event that I need to replace some parts, where can I get “quality “parts?

 

How did you fix the choke plate from getting stuck?

 

Swapped out the ignition module. Not the fix. Carb is definitely getting gas. I will check to see if there is a spark and also pull the distributor cap as suggested. Anything else?

 

You probably know, but there are different ignition modules for different years. Did the colour of the grommet match with the one you swapped?

 

I actually don’t know much at all...about most things!

if by grommet you mean the connections with the male and female receptacles, yes, they were both the same color. Black.

 

What is meant by "grommet" with these ignition modules is the plastic molded wire strain relief where the wires actually exit from underneath the box itself. Not the connectors out at the other end of the wires, which is what it sounds like you meant.

So look at the color of the plastic where the wires exit the box. It might actually still be black, as that was one of the colors. But there were many others, so make sure it matches the original one in that regard.
If it does not, there are a couple of models that are compatible with each other, and NumberDummy and some of the others will know if yours is compatible.

Also look at the backside of the original one for signs of overheating. As in melted potting material.
And while you're at all this fiddling, disconnect the 3-wire connector at the distributor and measure the ohms/resistance between the Purple and Orange wires. Should fall between 400 and 800 ohms.

Paul

 

I pulled the distributor cap. If by the “reluctor wheel” you mean the piece in the center, it was not loose.

when you say to hold the distributor and of the wire half an inch from the engine, do you mean it should be half an inch from the engine block?

 

thank you for the explanation on the grommet . Both of them are the same color, blue. The one that I pulled off was not the original. It does not show any signs of overheating. In fact, it looks fairly new.

 

Check the "horseshoe" connector at the coil. Could be losing contact . New connectors available at NAPA.

 

cleaned the connectors on these. They were questionable. What doe they go to?

replaced the coil. added dielectric to the cable. It was dry.

started right up. Not a strong start up, but it stayed running. Took it out for a run and it actually had more “zip” after changing the module, coil, applying dielectric, and cleaning horseshoe connections. Does this sound normal?

i am staying in for the night and am anxious to see if it will start up tomorrow.

thank you for all the input!