Starting problems / ignition / distributor

[GMCTom]

Hi everybody,

hope someone can help me with my problem.

In October 2025, I took the last ride of the season. Suddenly, the car died at walking speed. No sputtering or stuttering, no warning. It just shut off, as if the ignition key had been pulled out. There was no way to restart it. The starter motor turned, there were no unusual mechanical issues or noises. I then towed the car home.

The following points were checked:

- Fuel: present, also in den carburetor
- Spark: present but weak
- Carburetor: no issues
- Other mechanical issues: none to see, nothing to hear
- Distributor: still in the marked position (not rotated)

The following work was carried out:

- Distributor: points replaced
- Ignition coil: replaced
- Spark: now present and strong
- Starter: replaced (turns like a dream). The old one was a bit weak.

Result: Won't start

Here's what we found (many thanks to David/Prowbar here from the GMC forum ):

- Engine set to 1 TDC, valve cover removed, both valve springs on cylinder 1 are relaxed. Valves closed.

- Distributor cap removed. Distributor rotor points to cylinder 6 and not cylinder 1 (see photo). Engine turned 10° by hand. Spark on cylinder 6.

- Distributor pulled out: no abnormalities except that the vacuum mechanism isn't working. It's extremely stiff.

My question: I'm able to install the distributor so that it points to cylinder 1 and try to start it. Is that a good idea?

I'd like to know why the distributor position is incorrect.

At first, I thought the crankshaft and camshaft were misaligned, but both valves close at 1 TDC.

The timing chain was replaced during the restoration (200 km ago). Could the woodruff keys have sheared off? I think you'd hear that, and the valve position would be off.

Maybe you have a suggestion for me. I'm at my wit's end.

Many greetings

Tom

[FetchMeAPepsi]

I sure would like to help, but you're in over my head. Maybe Prowbar will pop in later and offer some insight.

[James]

Did you check the centrifugal advance in the distributor? If the springs had broken it would go full advance while running. Turning the rotor by hand the distributor should rotate clockwise against the springs. There should always be some spring pressure on the rotor and no looseness (no spring pressure/feel sloppy). Another possibility if you had just operated the engine to over 3500 rpm, it is possible that the centrifugal advance had stuck in the full advance position from dried up lubrication.

You can see if the engine will run by resetting the distributor to fire on the crankshaft timing mark. If it run OK, then you rule out other issues. You will need to repair or replace the distributor.

[AZKen]

Do not remove distributor.

Cap off, all plugs out. Thumb over cylinder 1 hole. Turn motor with starter. Watch rotor. See where rotor is when pressure hits thumb. Watch several rotations to see if rotor repeats. report.

Also, where is harmonic balancer mark when rotor is in position shown in your photo?

[beerman]

Did you move the distributor? Looks to me like the vacuum advance has been turned counter clockwise maybe you timing is too far retarded. Like AZken said check that balancer mark