I have a 62 f100 that has a 74 351w in it that i bought a couple months ago. The issue im having is that when i start the truck it runs for about 30 second to a minute then shuts off suddenly. Theres no stutter or shaking of the engine so i don't believe it to be a fuel issue. Ive replaced the regulator, battery, and alternator... just going through the basics. The spark plugs, distributor, and ignition coil are all relatively new as well. Thought it could be the ignition module but any help or advice would be great.

 

Its cuts off as if the ignition switch was turned off.

 

It's probably best to confirm whether it's fuel or spark that's missing. After it stops, look down in the carburetor and move the throttle. You should see a squirt of fuel. Or check for spark. After you're sure which is missing it's easier to pursue the problem. It could be the module. Also remember: "new" doesn't always mean "good". Always try to confirm component performance.

 

It's usually not a good idea to replace charging system parts when you have an engine running issue. Unless you measured voltage while running and found that the alternator was not charging, then this has nothing to do with an engine not running shortly after it was started.
A low battery will certainly be able to stop the engine eventually, but not 30 seconds after starting. If your battery can crank the starter to the tune of 120amps or more, it can certainly feed the ignition it's 10 or 15 at the most.

Do you have diagnostic tools, such as a volt-meter and timing light? If not you should be able to borrow them from the local stores on their "rental" (really a loaner) program.
Those can tell you quickly what your problem is, or is not at least in a few categories. A timing light will tell you if you're getting spark when you're cranking the motor.

By the way, what happens after it dies? Do any other power accessories stop working? Or just the engine stops running?
How long after that can you get it re-started? Does it start any time, then just dies? Or does it not start at all for a period of time?

Paul

 

i do have a volt-meter but havent gotten a timing light yet. Ive looked at the voltage of the battery and its not dropping considerably when i crank it. I cant crank it again right after it cuts off. The truck doesnt really have any other accessories being a 62 so i couldnt really tell you the answer to that one. It doesnt want to start up everytime either. Seems like it struggles for a while before it cranks over but when running its smooth.

 

i do have a volt-meter but havent gotten a timing light yet. Ive looked at the voltage of the battery and its not dropping considerably when i crank it. I cant crank it again right after it cuts off. The truck doesnt really have any other accessories being a 62 so i couldnt really tell you the answer to that one. It doesnt want to start up everytime either. Seems like it struggles for a while before it cranks over but when running its smooth.

 

Has it been running long enough to test it while running? You'd be looking for about 14.5v when running. Anything over 15.5 is suspect (usually a bad regulator or wire) and anything below 13v is not charging the battery sufficiently.
Not dropping substantially while cranking is actually kind of unusual. Sometimes it goes down a lot, even when things are working as expected.

By "crank" you mean fire up, or that the starter does not crank the engine at all?
Just making sure we're on the same page.

Yeah, nice and simple. But by accessory, I meant anything like headlights, horn, turn signals, radio, heater, white sidewall tires(!), and all the normal stuff.
What I was looking for was a clue that it might be a main battery cable or something like that. In which case it would not crank at all either of course.

So cranks over is starting, but when you say struggling, do you mean that the starter turns the engine over slowly, like it's got low voltage or is very tired? Or that you have to crank and crank and crank it for an extended period of time before it starts?
Each little clue "might" be the one that leads us down the right path.

Paul

 

You have to crank it for extended periods of time for it to start. But ill try and look again at the voltage when its running, dont remember the exact voltage. The starter works just fine. Itll turn no problem, given it has enough power. The long cranks kill the battery so i usually start it while jumping it. The battery holds a charge, ive checked that as well as the alternator working correctly.

 

The lights and blinkers and what not do work when it cuts off

 

Did you say it has a ICM on the inner fender?
Then it would have electronic ignition right?
If so try a new ICM to see what happens.
if not it you have a spare and they are not much money.
Dave ----

 

And even before trying the new parts, the next time it dies measure voltage at the coil positive and the ignition module positive (Red wire usually, but check White too).
And even though this is a '62 truck, how's about taking a couple of pictures of the engine compartment so we can see what's been used and where. Might give us some clues to work with.

Have you also tried the '62 forum? Not trying to move you out, since I like a good mystery too. But they're likely just as versed as we are, because the motor model year does not matter when it comes right down to it. So what you have is a '62 with a motor swap.
Unless the wiring for the whole truck was changed to the newer stuff, there are things we might not know about your model year truck that could come in handy.

Hmm, one of which might be the susceptibility of the ignition switch to melt down like some later trucks did.
Next time you're feeling flexible (or have a nice mirror-on-a-stick handy!) get down under the dash with a good light and inspect all the wires that meet up at the back of the ignition switch. Anything that looks loose, worn, frayed or burned/browned from heat, pull it out and fix it. You might just be running afoul of an overheating wire condition that's killing power to the ignition.

And on a different tack... Vehicles that have sat for extended periods of time often have failed, or failing fuel pumps. So that test mentioned earlier to pull the air cleaner off and look for fuel squirting with the accelerator pump is important. Since you don't know the engine's history, you could be dealing with all sorts of issues rather than one.
And this fuel pump issue is not some bad dream. It's an all-too-common reality for way too many people these days. Modern fuels combined with the crappy parts we have these days is a bad combination.

But on a good note, I just found an old Mag-Lite in the back of my truck I had not seen in many years. Like over 20 years. Pushed the button and it worked.
No big deal maybe, but I looked at the batteries that were still nice and clean with no white flashlight-killing gunk, and they were dated "Best Used by July 1994"!!!!!!!
Now that's when men were men, and batteries were worried! And made in the USA still...

Paul