DIY-ER, years ago, my son's 1984 [4.9L] with feedback ignition/carburetion started acting up. It would barely run with great care [throttle feathering, etc.] and shook like crazy! It made all sorts of clicking and clacking noises. I thought a pushrod was bent. The electrical pick-up in the base of the distributor was bad and the clicking/clacking noise was the 3 solenoids mounted on the valve cover [rear] on the driver's side, in response to the wildly varying vacuum signals.

His was repaired with the replacement of the pick-up and has not repeated that. When I purchased my 1986 with the same ignition/carburetion system, the decision was made to do the Duraspark conversion due to so many problems with what was on the truck. You are already almost 1/2 there [Duraspark conversion]... if where you live, you do not have to pass emissions, think about completing the conversion. You already have the most expensive part [carburetor] and rebuilt Duraspark distributors are not too expensive.

There are many threads available detailing this, so be sure to read before acting. Here is one: https://www.ford-trucks.com/forums/9...-86-i-6-a.html

 

Definitely run the voltage drop test as linked earlier. It is just three quick readings with a voltmeter.


If those three readings are good, see if you can duplicate the jammed no-start condition at home, but don't bump the engine to another spot. Remove the starter and look at the teeth on the flywheel at that spot. Could be the teeth are very worn at that place, and the starter gear climbs and jams when engaged. When you were bumping the engine with the clutch, it may have been turning to a fresh spot where the flywheel teeth are good.





Piece of cake. First run the voltage drop test to make sure the battery cables are good. Then hook up your voltmeter to the battery posts. Rev up the engine to around 1500 RPM or so. You should see at least 13.5 volts to show the alternator is charging.

 

Ouch!

One up for you ...

-Enjoy
fh : )_~

 

The only choke issue that I have right now that I am aware of is that the heat riser coming from the exhaust manifold has rusted out. I plugged what was left of the riser going to the choke. The choke is the kind that is electronic and uses the heat riser. So it is probably opening a little too slow.

When I replaced the positive battery cable I also replaced the ground wire going to the starter. My original wire had a section of insulation cut out of it at the mid-length of the wire where the bolt is that attaches to the truck. I am guessing was to allow the wire to ground to the truck. The replacement wire did not have this. It is fully insulated from the battery to the starter. Not sure if that hurts anything.

 

If that is what it is you are crazy good. I would have never thought of that. I wonder how often that happens. I will need to right all these things down. You guys are throwing me good ideas left and right.

 

I have been thinking about that. I wonder how hard it would be to convert back if I move to where emissions become an issue.

 

My thoughts on the choke are that it might not be operating correctly at all, not just opening more slowly.

IOW the kind of symptoms you describe would have me opening the hood, removing the air cleaner assembly, go start the engine (after having sat overnight) and then observe the choke plate, verify that the thing is even working (correctly) at all, summertime temperatures can hide a lot of issues that would really make themselves known in December.

 

When the truck is cold the choke is closed up. It does open all the way as it warms up. So it should be good there.

 

Oh yeah, you'll want to ground the frame. With your current setup, the frame is electrically isolated from the batterry and engine block.

You likely can't find another original ground wire with the terminal in the middle. You can create an equivalent by running a separate ground cable from the frame to the bolt on the engine block where your current ground cable is attached. That should take care of it.

With the frame not currently grounded, you could have all sorts of electrical weirdness going on. Your alternator, for example, could be going haywire without a valid voltage reference signal. The ignition system could be off in the twilight zone, too, especially if the alternator is putting out voltage spikes.

Did you have the drivability problems before replacing the ground cable? If so, it almost sounds like two problems. The first was a damaged ring gear on the flywheel, causing the starter to jam and damage the solenoid and cables. With new cables, the erratic behavior started but that was likely due to the now ungrounded frame.

Even if that wasn't the scenario, correct the ungrounded frame. Even if that isn't the cause, normal troubleshooting is to fix any known faults before getting too deep with other stuff.

 

I can't recall if the bouncing tach and dieing issue happened before or after that. I know that sounds crazy to not remember but i have only been able to work on it on and off. So by the time i get back to it i have to figure out where i left off. I know it did not want to start. Which is why I replaced the starter, wires, and and fried solenoid. I am out of town for the weekend but will ground it as soon as I get home. I think you may be on to something. Thanks.

 

Don't forget about the ground between the engine and the body (cab).

 

My son and I recently replaced the ground strap on his 1984 with 4.9L engine. As mentioned previously, the replacement ground strap did not have the metal tab midway between the battery and starter motor bolt, for grounding the frame, so a 2nd 20-24" cable with eyelets on both ends was used. One end was attached to the same starter bolt used for the battery to starter motor ground and at the other end, it was attached to the original bolt for frame grounding [approximately midway between the battery and the starter motor].

 

Ok... I think it may be fixed. As previous posts suggested I added another cable from the starter back to the original ground location that was used by the old cable. I did observe a couple of oddities that I would like your takes on. I have my own theories. Let me list my steps -

• Added new cable going from starter ground to frame.
• Hooked battery back up. (Since I rarely drive it I have a cut off switch for my battery so it does not drain.)
• Started the truck just fine. I did not even have to hold the gas in to keep it from dieing like I had been.
• Drove around and could not get it to die.
• Turned off the truck and unhooked the new cable to test if the problem would come back.
• The truck would not start. The starter acted like it did not want to turn. So I temporarily hooked the new ground back up and it started.
• With the truck restarted I unhooked the new ground and the problem started to come back. Problem solved... I think.
• I hooked the new ground back up and the truck would not start. Crap. But this time it just slowly turns. Sounds like a low battery. I charge it up and it starts.
• Now this is where I want your thoughts... With the ground hooked back up it is not running as smooth as it was when I first test drove it. It seems like it wants to die just a little. It does recover but it is enough to make me nervous. My theory is this... On my very first test drive the battery had been unhooked and therefore the computer would have been wiped clean. On my second test drive without the new cable hooked up I could have caused some issues with the computer that did not go away when I hooked the cable back up.

So... Could the computer have "learned" some bad data without the ground, and could this cause problems when the ground is hooked back up without clearing the computer first? Or am I giving the computer of a 1986 vehicle too much credit?

Thank you all for the help.

 

Next time you're consumed with the urge to unhook that new cable again, please do me a favor. Stand up straight and step away from the truck, and then hold still. I need you away from the truck because I don't want to chip the paint if I miss when firing the tranquilizer dart gun. It's the only reasonable course of action we can take to get you to stop 'fixing' what may no longer be broken.

All seriousness aside, sounds like you've made some great progress. Until you rack up some miles, we can't say for sure if everything is fixed, but it does sound like you've cleaned up one major contributing factor.

I don't know about the learning capabilities of a 1986 computer, but your theory sounds reasonable. Most vehicle computers do exactly as you were thinking. You'll need to log a few hundred miles to be sure the problem is fixed. Don't disconnect the battery until then. After a disconnect, the computer may be using some preprogrammed values for a little while, and this can mask other issues.

 

I hear you loud and clear. I cannot believe that that would have caused so many issues. The original wire was different from what I had available from Auto Zone so I purposely ordered it from LMC thinking I would get one that matched stock. When I got it I thought well I guess it does not need it. Mistake #1: Don't assume the original ford engineers did something just for the heck of it.

Mistake #2: I replaced too many things at once without being able to check the results of each "repair". I had my gas tank off the truck so I was not able to test drive it during all of these "minor" repairs. This left me unable to catch the mistake.

Mistake #3: I waited too long to enlist the help of you guys.

In the next few days I will be trying to tune the carb to get the idle just right. I think I need to replace the fuel/air mixture screw. When I rebuilt it I noticed that there was a little (just a little) wear on it where it was probably seated too tight. When trying to adjust it I cannot tell if it is "fine tuning" things as well as it should. It either is out too far or in too far. I think I really just need a lesson on how to tune a carb. Under the hood it says I should disconnect the water temp sensor when adjusting the idle. Is this still valid since I have the non-feed back car instead of the feed-back? Is there anything else I should do prior to adjusting the carb?

Thanks again.