Help.... truck runs for awhile...then dies

Ok so put ome highway miles on my F100 the last couple weeks... all good..stock 352 3spd..keep it at about 2 grand 63 mph..went to visit a bud about 20 miles away..got half way there and the truck just died... fell on its face..I clutched it to get it running again, it fought a little , but I did get it home. Did the usual things, checked for fuel from main line, fuel came out , changed the stock canister fuel filter, the 18" of rubber line, and the in line fuel filter, I also know I have fuel pressure, pulled line from pump and sprayed into a pop bottle, also the car will fire up and idle.. for about 5-10 minutes..than just dies, and it will fire again..just not quite as easy as when cold, motor is not overheating running at 180,.. I thought hmm bad coil? changed that out fired it up in the drive..10 minutes she died again. It has a accell conversion in the stock distributer, battery reads 12.9 volts, My next plan of attack is plugs and wires. theresboth due to those lovely leaky FE valve covers... The vacuum lines appear to be in good shape..man I cant catch a break this summer!

 

I would be looking at that accel conversion.Maybe throw a set of pionts back in it.

 

Do you have a vented gas cap?
Or a good vent for the tank?

 

Where is you fuel filter. Before or after the pump.

 

x 2 I once had a Mallory Unilite conversion on a chevy 6 cyl that would run great but would die in the most inappropriate places and refuse to start again until the dist cap was removed and reinstalled. Mallory replaced it after I contacted them but the replacement would do the same thing so it ended up in an appropriate trash can, replaced by a factory HEI. problem solved!

 

Next time it quits, look to see if there is any fuel in the carb before you try to start it again. I had a fuel tank that had some crud in it that made my car do that. You need to determine if it's a fuel or spark problem.

 

Make sure you ave a vented gas cap. HRP

 

could be the float sticking

 

Run it with a temporary gas tank (boat) straight to the carb and see if that fixes it. If not dump the Accel parts for something else. Pertronix is good unless you think cleaning and adjusting points is fun. Could also be spark wire from coil to dist or possibly you are loosing power to ignition as in bad ground, fuse, wire, etc. Most intermittent heat related problems are electrical in nature from my experience.

 

I concur, junk in the tank or fuel tank creating a vaccuum...

 

I had a truck that would do the same thing, turned out that someone lost one of those little foil seals on the bottle of dry gas and it was getting ****ed onto the suction tube.

 

The strange thing is it just started. I have owned the truck for 2 years and its been awesome

 

Sounds ignition related, not fuel. Check the little screws that hold the Accel ignition module and magnet in the dizzy. Make sure they are tight. Check the ignition wires on your ignition switch, make surevtheyvare tight. If youre running a ballast, check connections there too. Start with the easy ****, it's usually something stupidly simple, yet overlooked looking for major problems.

 

Sometimes a coil will heat up, short out and die. Then it will cool off and start right up again.....and then do it all over again.

 

Replaced that already

 

Unless you feel lucky the best thing is to isolate the problem, narrow it down.

Spark, Fuel, Compression.

Compression:
Possible but least likely for your scenario. Compression doesn't usually fix itself. I have seen stuck relief valves overpower lifters but that's normally cold.

So now we come to a Fork in the road.

Spark or Fuel

Easiest to check is Spark, carry a spark gap tester set to about 20 KV.


Attach to coil wire and ground, if you have a blue spark then you are good to go.

If not in order of likelyhood of failure, and electronic module is susceptible to heat.

And the biggest cause of those failures is a poor thermal connection between the module base and breaker plate.

I would get a fresh tube of grease and remove the module and thoroughly clean both surfaces and apply a thin film of conductive grease.

Of course be sure at idle the coil has about 6-7.5 volts applied to the positive terminal, more than that and you don't have the right coil/ballast resistor match. This will overheat a module.

Fuel:

Tee in a fuel pressure gauge and run it up and tape it to windshield, observe.



You can get non-professional versions of both tools for a total under 25. A must for every rodder.

 

Stock has tank, I'm leaning towards the accell unit. Like I said of I pull the rubber line coming off the main fuel line it flows fine. Pull the air cleaner got fuel spraying at acceleration and again it's idling fine

 

Before you buy something new try the heat sink grease and check coil primary voltage, jm2c

 

Doing that tomorrow, thanks for the tips guys, I know the 4 things it takes to get a motor running, got compression....it fires, has good idle, got fuel..checked pump, carb, revs,idles, not loading up, or going lean, air...can hear the carb ****ing and doing its job...so I'm with all of you and thin it's ignition related. I'll let ya know what I figure out....keep the suggestion up though. Thank you all

 

X2 on monitoring fuel pressure real time.

If you can make it act up idling in the driveway, I'd hook up a timing light and watch the timing mark. It ought to spark strong and steady as it stalls if the ignition's good.

 

This will drive you nuts if unaware of the possibility.


the next time it stalls, give it a squirt of carb cleaner or ether and try to start it. If it putters and runs you have a fuel problem. No putter and you have an ignition problem.

Have you done your silly fuel test while on the side of the road in its screwing up mode? Or at home in the drive way while it was in its running?

 

Does your truck have a ballast resistor or ballast resistor wire? My "65 Biscayne used a ballast resistor wire and I had the same symptoms when it went bad.

 

sounds like distributor to me???

 

I had pretty much the same issue and it was the condenser had a small crack in the insulating material

 

Sorry did not read you converted my bad

 

ok well that in line spark tester worked awesome. It aint ignition. I had it running while testing spark and it died. I went to fire it back up and she backfired through the carb with a puff of smoke....like not enough fuel. I am gonna get in the tank when the family is sleeping tonight. Ill pull the sending unit and see how it looks. I didn't test fuel pressure..I am ***uming I got it cause it starts and idles, but could be wrong. Also I did have fuel coming out of the tank when I pulled the rubber line off, but it was one of those " rip the old line off, hurry get the new line on" kind of tests. Its a stock non vented tank. I also ran it without the fuel cap to see if that made a diefference. Motor is a bone stock 352 with a motorcraft 2 barrel. I have also checked the distributer is tight on the motor..Timing has not been touched

 

make sure if it has screen in fuel inlet fiting at carb it is not pluged ,check jets in carb are not pluged

 

Same happened to me, replaced plugs, wires, cap, coil, ballast resistor and my truck would die. I cleaned up the carb screen and filter, added a fishbowl filter and the problem went away

 

"... had it running while testing spark and it died."

If I had my fuel pressure gage hooked up close to the carb while that happened I'd feel I really knew "something" about the condition of the fuel pump, and everything else upstream of the pump, like filters, inlet sock, any rubber hoses on the inlet side of the pump, and gas cap venting.

Does it have a mechanical choke? Closing the choke briefly when starting to act up will coax gas out of a carb with low fuel level, or droplets of water squatting over teeny holes that are supposed to be letting gasoline in.

 

Had similar problem on my old 9n swore up and down it was the coil. Replaced that and it was the screens in the fuel system although the coil really helped it run better in between it shutting off. I would go to a pertronix coil and module just to rule that out and rig up a fuel pressure gauge to wat h what happens when it dies