1978 k25 stalling issue

papapavs1 · Aug 30, 2024

Hello, I have a 1978 k25 with a 350 engine. The previous owner installed a new ignition switch and distributor. Ran great for a while, then started intermittently dying on me. I first ensured I had good voltage to the HEI, which I did. I replaced the distributor, which didn’t seem to do anything. It starts, will run for a few minutes, and will then shut off, and will then seem to stall more frequently after it first dies and is restarted. I am thinking of replacing the ignition cylinder next as I know that was replaced with presumably a Chinese one, unless someone has other input. For what it’s worth, I did do some welding on the truck with the battery still hooked up by accident, but I drove it a few times after with no issue.

papapavs1 · Aug 30, 2024

Correction: Previous owner installed new ignition cylinder, not switch.

Snoots · Aug 30, 2024

Probably a fuel problem.

fast 99 · Aug 30, 2024

Before tossing parts at it why not try diagnosing first? As suggested above check fuel pressure and volume. Ethanol is not friendly to old fuel systems.

papapavs1 · Aug 30, 2024

It doesn't sputter at all, just dies so I wasn't suspecting fuel. I was watching the carb while lightly revving it one time when it died, and it was spraying good the whole time.

fast 99 · Aug 30, 2024

When you get done shot gunning the problem we will still be here.

Ricko1966 · Aug 30, 2024

It's not your lock cylinder or the ignition switch if you have good voltage at the HEI when it dies. If you are uncertain take a piece of speaker wire split each end so you can attach one of each wire at one end to a 194 bulb, when you have the bulb in front of you, you will see where to bend the contacts up and twist the wires on. Other end connect one lead to alligator clip and clamp it to a ground. The other lead twist it onto a safety pin. Stab the safety pin through the backside of the HEI 12V connection. Now your distributor is connected and a 194 bulb is piggybacked into the circuit. Stick your bulb under 1 wiper so you can see it. If the lights on when the truck dies,key cylinder,adjustment and ignition switch its self are ruled out.

Ricko1966 · Aug 30, 2024

fast 99 said:
When you get done shot gunning the problem we will still be here.

Maybe we'll be here.

Grit dog · Aug 31, 2024

Ricko1966 said:
It's not your lock cylinder or the ignition switch if you have good voltage at the HEI when it dies. If you are uncertain take a piece of speaker wire split each end so you can attach one of each wire at one end to a 194 bulb, when you have the bulb in front of you, you will see where to bend the contacts up and twist the wires on. Other end connect one lead to alligator clip and clamp it to a ground. The other lead twist it onto a safety pin. Stab the safety pin through the backside of the HEI 12V connection. Now your distributor is connected and a 194 bulb is piggybacked into the circuit. Stick your bulb under 1 wiper so you can see it. If the lights on when the truck dies,key cylinder,adjustment and ignition switch its self are ruled out.

I love all your old school diagnostic hacks/advice. Reminds me of a better time! lol. When you could diagnose a car problem with a safety pin and a light bulb!

1978 k25 stalling issue

papapavs1

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fast 99

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