Engine start issues

[Weasel74]

I have a ‘74 Cheyenne with a 350, th350, rebuilt Q-jet carb & new gas filter, new gas tank, sender, and hose lines, new fuel pump, new coil, plugs, points, rotor and condenser. The engine may crank for a few seconds and die off. The dwell is correct and the timing was not moved when it was running. I have set the idle mixture screws at 2 turns out. I have checked plug wire sequence and all vacuum lines are connected.
Any suggestions or help is greatly appreciated! Weasel74

 

[Truck82]

I have a ‘74 Cheyenne with a 350, th350, rebuilt Q-jet carb & new gas filter, new gas tank, sender, and hose lines, new fuel pump, new coil, plugs, points, rotor and condenser. The engine may crank for a few seconds and die off. The dwell is correct and the timing was not moved when it was running. I have set the idle mixture screws at 2 turns out. I have checked plug wire sequence and all vacuum lines are connected.
Any suggestions or help is greatly appreciated! Weasel74

The starter dies off and won’t crank the engine? If that’s the case it’s most likely in the electrical.

 

[Ricko1966]

When you say crank and die off,do mean the engine starts and runs briefly?

 

[75gmck25]

Make sure you have 12 volts to the distributor in start and run positions. The rod connecting the key mechanism to the electrical switch make be flaky, and the switch is not providing power to the distributor in both positions.

I would also try a cold start by pouring a few ounces of gas into the primary side of the carburetor, and then reinstalling the air cleaner (in case of backfire). If it then starts and runs for a short time, it’s a fuel delivery problem. Time to start checking the Quadrajet fuel filter, float level, needle, etc.

 

[Weasel74]

The starter dies off and won’t crank the engine? If that’s the case it’s most likely in the electrical.

No -the starter is Ok. It cranks the engine fine but it dies after a few seconds-crazy!

 

[Weasel74]

When you say crank and die off,do mean the engine starts and runs briefly?

Yes -for a few seconds and stops

 

[Weasel74]

Make sure you have 12 volts to the distributor in start and run positions. The rod connecting the key mechanism to the electrical switch make be flaky, and the switch is not providing power to the distributor in both positions.

I would also try a cold start by pouring a few ounces of gas into the primary side of the carburetor, and then reinstalling the air cleaner (in case of backfire). If it then starts and runs for a short time, it’s a fuel delivery problem. Time to start checking the Quadrajet fuel filter, float level, needle, etc.

What is the best way to check if 12 volts is going to Distributor in start and run positions. I’m kinda a rookie in this area! Thanks

 

[Ricko1966]

If it is starting its getting 12 volts at cranking,if it starts and continues to run a few seconds after you release the key it's still getting 12 volts.If it starts and dies it is most likely a fuel related problem,try wedging the choke plate open 1/4 inch or so,a wooden clothes pin works good, pour a tablespoon of fuel down each of the primary barrels try to start the truck and keep it running with your foot,try 2 or 3 times. Does it start and run then? Keep some dry rags handy,sometimes they'll back fire and light off any fuel you've dribbled on the top of the carb. NBD smash the rags down it will snuff right out. Doing just this will answer several questions. Let us know the results.

 

[Ricko1966]

I gotta go,busy busy today look at the pic below the hole I'm pointing at if you pull off and leave off for now the big hose directly ahead and below that,then fill the carbureator through this hole,use a mustard bottle or a dish soap bottle .About an 1/8 th of a cup if you fill it too much fuel will dribble out where you pulled that hose,i just fill them till they dribble. If it starts,runs,revs feels normal for about 10 or 15 seconds. I'd look at fuel delivery. Issue's. I'll post more later.