1978 ford F150, 3300 miles on new motor. Runs great---except it will die running at speed going down the highway. Standard transmission, and can leave the clutch engaged and wait about 100 yards and it will take back off and run fine for a few miles then die again. It has never failed to start running again. I am thinking brain box issues. I replaced the original box last year after it quit. Replacement was an autozone special, which I know are not reliable.

Any other suggestions?

Thanks in advance!!

Joe

 

does it do this only when hot or also when cold?

If only when hot, could be distributor pickup, coil, brain box, etc.

 

Only when hot. It always starts fine,

 

1. Change the fuel filter.
2. The next time it dies, quickly check for spark from the coil and at a cylinder.

 

The 3 step scenario of a failing DuraSpark ignition module.

1) Module overheats, engine dies. Module cools down, engine restarts within a few minutes.

2) Module overheats, engine dies. Module cools down, engine restarts in a hour or so.

3) Sooner or later, usually sooner, the module overheats, BURNS OUT. Now the engine will not restart.

Taking the little charmer to an autoparts store to be tested: Unless burned out, will test ok, because it only fails when it overheats.

Module located on the left fender inner apron, just in front of the firewall.

Engine heat, especially radiating from the V8's red hot left exhaust manifold...is the mortal enemy of these modules.

If replacing, use some washers to space it further away from the apron. The more airflow around the little charmer...the better.

The modules used in the 1970's were sooo unreliable, that Ford techs referred to DuraSpark as NeverSpark!

 

New ignition module as well as a new fuel filter. Drove about 25 miles with no problems. Keeping fingers crossed!

 

It started shutting down at highway speeds again. Same symptom. It is just like you turned the key off. This time I did get to check the see through fuel filter and there was fuel getting to the carb. It must electrical......? Might try another coil next.

Carrot66

 

Same problem, truck starts misfiring around 60 or 65 and than shuts off, I changed fuel filter, and coil next it the ignition box, anyone have any good ideas on a new ignition box? Like MSD or Crane? Not trying to jack thread what so ever just trying to help give insight and get some feedback as well.

 

One of mine would shut off while driving and would not restart by popping the clutch. Had to turn the key off and start it as if it were stationary. Didnt need to wait, could do it while still rolling through traffic. Changed the box, distributor and eventually the starter solenoid. Been a couple of years now and no more problems. Those are all parts that I keep on hand so it wasn't any big deal but it was simply the starter solenoid.

 

The starter solenoid is a good thought. But you should at least get a clicking sound like you would with a dead battery. That is if you try restarting by using the key. Here's another point to keep in mind. I had this happen once with my bronco. Check the automatic choke if your truck still has it. Mine went bad on my bronco along time ago and gave me the same symptoms for a while. Then one day it just stayed shut and wouldn't let the truck refire. But at first once it cooled down for a few seconds the choke would open enough to let air pass into the carb and the truck would run. But once it got to just the right temperature the choke would close completely and suffocate the carb and the the truck would stall.

 

New dist. cap, rotor and coil. Started up and ran great. 15 miles later, I was on the hook. Stalled and would not re-start. Same symptoms as before with the exception of fuel dripping into the secondaries (as looked down from the top) on the Holley 650 and fuel dripping out the passenger side of the carb.

WTF? I guess carb. is coming off next looking for sticking floats.

That is when/if I get the truck back home

 

I had a similar problem and long story short it was caused by old rubber fuel lines. If the truck was sitting for a while and the fuel drained out they were hard and stiff. When wet with fuel while running they got as soft as cellophane. Pump suction pulled them shut and the truck stopped... but would re-start in a few minutes and run for a while.

A few feet of rubber line and a couple of hours fixed it. If not done already, suggest you replace every inch of rubber line.

Another potential problem is crud in the fuel tank. It collects on the strainer sock enough to plug it and shut it down. After a few minutes some of the crud falls off and it runs for a while. Pulling the tank pickup for a look see can diagnose this problem.

 

Tonight was remove the carb night!! What I found was a big hunk of crap between the needle and seat on the secondary side. Removed and re-assembled everything. Drove for a while with no problems and no more fuel leaking. I guess there was enough fuel leaking out and into the engine that is caused a flooding condition.

Time will tell.

Carrot66

 

Well--Another tow bill last night. Truck had been running fine since replacing some cracked vacuum lines.

So after replacing:
The coil
The cap and rotor
Fuel filter
"Brain box"
vacuum lines

Still died running......No spark at the coil wire. 12 V at the coil.

After much reading on this site,. I decided to rig up a test light on the TACH side of the coil to see if it pulsed during starting. It did not, so I went about replacing the distributor pickup. After I pulled the dist, I decided to just get a new one as the original was pretty "used".

Side note: whoever the gentleman was that posted about using a 5/16 socket and grease to center the oil pump shaft----I owe you a 6-pack. That tricked saved me from bashing a new distributor to pieces.

Anyway---new distributor installed and the truck fired right up. Tried the test light thing again and it pulsed as it should.

I hope this is the end!!!

 

Are you sure there isn't a second fuel filter at the carb inlet? If so, replace that. A trick to isolate the problem if it re-occurs: When it dies, try to start it. If it doesn't, give it a small shot of ether and crank again. If it fires, it's a fuel problem.
Eric