help me figure this one out, Ive been having a problem with me recently acquired truck, it breaks down every single time I drive it, and I have to tow it back home. When Im in town doing 30, it drives fine, but when i leave town and start accelerating up to 55 - 60 it doesnt take long for it to die, and then it wont restart, I take it back and tinker with it and Ill think I fixed the problem, and then when Im leaving town, getting up to highway speeds it cuts out and dies, it keeps doing this no matter what I replace, this truck has a 360, all these parts have been replaced within the last 2 weeks, new carb, fuel lines, fuel filter, electric fuel pump, plugs, cap, rotor, wires, pertronix ignitor, vacuum advance, and battery, each part above came from a time it broke down, and I thought I figured it out, I went through 2 mechanical pumps, before I chose the elec one, today is when I decided to replace my vac advance, it seemed to sound better after the install, coulda just been the nice weather, but instead of taking it for a test drive and getting 10 miles out in the country, I decided to let it warm up in the driveway, it idled better than usual cold, ran fine, at about 15 minutes it died, I went out and was able to start it up, but it didnt run more than 5 seconds, and it died and wouldnt restart, this leads me to beleive this problem is related as to when the engine reaches a certain temperature. Every time it dies its like its running out of gas, you know, where it will run, and then cut out, run again for a second, and then its dead.
I know this was long, but if you could help me, it sure would make it easier to get to work! I need this truck to run.

 

Ok, when it dies, does the accel pump still shoot gas? That will cofirm there is fuel in carb.

You know....this sounds kinda familiar to an issue I had with my '69 a few years ago. It would randomly die on me and usually not start. Once I had to get trailer to tow it home, others I finally got it running again. It would just like start loosing cylinders, miss til it would barely run on 2 cyls with foot on the floor. Finally die and that's it. Fuel, spark but no fire. To this day I don't know what was wrong as I'd change things and it would be fine...then do it again. It's back to the old parts again and seems to be fine last year. It's a real mystery?

I was going to say it's the condensor, but you have Pertronix. I had one of those go south on me(it would basically ground out and kill engine). Took a couple hours to get that one figured out. It would run, then die suddenly. Seems condensor would get warm enough to fail. Once cold, it would restart and repeat.

 

check your coil it is heat sensitive.Are you still getting spark after it dies.

 

Just a guess, but with it being heat related, it might be the coil. Under hood heat kills a coil, especially if it is original and mounted on the engine.

 

I agree with electrical and coil is at the top of suspects.


John

 

I agree on checking the coil also. When you installed the Pertronics are you sure you have the coil primary wired polarity correct?

 

ok, heres my update, the problem persists!, I rerouted my fuel line way up outta the way of the engine, started it up, ran longer than usual this time, but at about 20 minutes of idling it died, I felt many components while it was running, and immediately after it died, nothing was too hot to touch ( except radiator), check fuel lines, fuel pump, carb, coil, they were warm but not too hot to touch, although as it was dying i squirted water on coil, carb, fuel pump and lines to see if cooling those off would help, it did not. There are a few things I noticed this time around, and they might be able to help you guys point me in the right direction.
I reconfigured my pump/filter routing, I had the filter before the pump, it is now after the pump, I blew through filter backwards over white paper to see any rust particles, it looked very clean, the things I did notice, were number one, my truck was overheating, not billowing steam, but just beginning to boil, it seems to me that it must be just beginning to overheat when it dies, acts like it runs out of gas, also I noticed my number 6 plug was arcing from the bottom of the boot to the block where the plug goes in, I could see the spark, in broad daylight and it jumped approc 3/4 inch to the block on every fire, also whatever sensor that is that screws into the front of the intake with a wire going to it, that wire is shot and needs to be replaced, it is bare in a couple spots. does any of this ring a bell in anyone? help me out please!

 

update again, let the truck cool most of the way off, hard to start but did start, reseated plug wire before i fired it, did not arc while engine was cold(ish), once it warmed up plug wire started to arc again, and truck eventually did the same dying routine, I also noticed that above my gas tank there are 2 wires, one connects to the terminal on top of the tank, the other is a ground wire that attatches to the back of the cab, the ground wire is not attatched to anything else, its just hanging there with a terminal that looks like ths solders broke loose, could this be why she dies when hot? wonder why my plug wire is still arcing

 

The wire to the front of the intake is for the temp sending unit. The wires on the tank are for the fuel gauge. With either of these wires loose or grounded it will still run.

 

This really sucks, what in the hell could be the problem? a head gasket, thats sealed when engine is cold, and opens up when warm?, the coil is old looking, but its never too hot to touch, I can hold it for however long I want and its not too hot, could the coil getting barely warm be enough to overheat the coil? Is there any other component that would kill it when hot?, Im ready to abandon my dream of my bump and get rid of it, I need this to run, its adversely affecting my life.

 

after it dies check the fire comming from coil wire,see if it's red or no existant
as others mentioned I would suspect the coil

 

This was posted in the 73-79 forum. It is something else to look at.

My '78 started doing that same thing last fall, drove me nuts, like you said it would just cut out like that ignition was turned off, no sputtering like a fuel problem.

Turns out the problem was at the electrical connector near the firewall for the engine harness - it has 4 wires I think, one being the primary feed to the coil - it was down to one strand of copper. No problem after I fixed it - now my temp gauge works better too, its wire was frayed as well.

Check the voltage to the coil. I think it should only be 8 volts. Not sure. Sounds like you are in need of a set of plug wires. Good wires don't arc past the boot. Will give you zing if you touch them while running! Did you look at the temp gauge to determine if it was overheating? Thermostat may be stuck closed. Don't give up hope! One of us will nail it for you!

 

It's overheating so take the belts off the fan and try to move the fan by grabbing a couple of blades. If the fan has wobble then look at the water pump bearing.

Also, (your situation reminds me I have to disconnect this) the overheated coolant is travelling through the carb spacer.

If you replace the water pump why not the timing chain, too ??

My truck behaved like your truck but the points had nearly no gap. You have electronic.

I do have electronic conversions in another application. Mallory. No solid core wires and must have resistance before module, either ballast resistor or built in coil. You're Pertronix but they may have their own requirements. Just hought I'd throw that in there in case Pertronix is the same.

That's all I know.



Enjoy

 

My first thought, like several others, is a coil problem, but you are going to have to check and see if you are getting spark through your wires when your engine gets hot and dies. If it will still fire but won't start then a fuel problem, right? Had the same problem a few years ago with a 400 engine in my truck. Drove me crazy till someone told me to try a 1" carb spacer, they said that heat from manifold was causing fuel to boil in the carb. I added one and it fixed my problem and you did say your trucks overheats. May be a place to start, maybe let truck idle while keeing carb cool with a small stream of water??? Good luck

 

You know how to change parts, but know zip about trouble shooting or tune up. You need to do what all these guys say. But here's the deal you really need you learn the steps of trouble shooting like 123456 .Ok plus you need a few tool to do it with. Like test light, ohm & volt meter and learn how to used them. And the the number one test tool is a jumper-wire about 4 foot long that can be used as a Hot-wire to by pass your key switch. These truck old or new if you have know idea what's what's when it stops running you had.
But the old trucks we have a chance to fix them with just a little know how.
Sorry to say but you need a motor Manual that covers your truck model..
The internet is no help when your broke down on the road side..
I don't mean to sound like i'm coming down on you,you just need some basic trouble shooting skills then you'll know what and how to check your old classic truck out and keep her running for yrs to come..
My 2cent
orich