Starts then dies

[Lumpymorg]

Truck starts then dies immediately when key springs back.
Replaced ignition switch and checked whole fuel system and it still won't run.
Any advice?

 

[Bextreme04]

Truck starts then dies immediately when key springs back.
Replaced ignition switch and checked whole fuel system and it still won't run.
Any advice?

Check to see if you have voltage at the coil when the key is in the acc and start positions. If you do, then you might want to start looking at the carburetor and choke. You might just need to give it a few pumps if its cold out or the choke pulloff might not be working right. Is this still a points distributor or has it been retrofit to HEI?

 

[JoeR Jr]

1) Confirm you are losing spark when it stalls
2) See if you are losing B+ to the distributor when you lose spark.
If you are losing B+, then chase that down.
3) If you have B+ to the distributor when it dies pop the distributor cap and rotor off. Give the wires from the pickup coil to the module (there's 2 of them) a LIGHT tug to see of one of them is hanging by a thread. If one wire pops off, replace the pickup coil.

The reason it would start and die is that as soon as you have vacuum the distributor turns and moves the wires.
Of course there are about 500 other reasons for the truck to die like that, but with that symptom, that would be where I'd head first.

Joe

 

[Dave M]

Truck starts then dies immediately when key springs back.
Replaced ignition switch and checked whole fuel system and it still won't run.
Any advice?

If your running an old points ignition, try replacing the condenser. Had the same issue on a MF135 petrol tractor at one time.

 

[Lumpymorg]

1) Confirm you are losing spark when it stalls
2) See if you are losing B+ to the distributor when you lose spark.
If you are losing B+, then chase that down.
3) If you have B+ to the distributor when it dies pop the distributor cap and rotor off. Give the wires from the pickup coil to the module (there's 2 of them) a LIGHT tug to see of one of them is hanging by a thread. If one wire pops off, replace the pickup coil.

The reason it would start and die is that as soon as you have vacuum the distributor turns and moves the wires.
Of course there are about 500 other reasons for the truck to die like that, but with that symptom, that would be where I'd head first.

Joe

I figured out the issue. On HEI setup power to the distributor comes from starter, but for some reason it wasn't getting enough power, after wiring power straight from battery the engined fires up and runs.

 

[Bextreme04]

I figured out the issue. On HEI setup power to the distributor comes from starter, but for some reason it wasn't getting enough power, after wiring power straight from battery the engined fires up and runs.

In 73, it would have originally been a points system. The points system has a resistive brown power wire that reduces voltage to ~9V going into the distributor. Often people will retrofit to HEI and not replace that wire, which will cause this issue. That's why I asked you in a previous post if this was the original points system or a retrofit HEI. The best solution is to run a new power wire via a 10 AWG wire from an IGN source on the fuse block or to have a new relay switching power on using the old 9v supply to switch power on directly from the battery.