VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 1928 Carter Carburetor RAKX-0

Having completed restoration of my 1928 4 door sedan, a problem has arisen with the engine running rough. We ran it in our shop several times for a total of more than an hour, where the engine ran smoothly and the exhaust was clear. Last month, on getting it out of the shop and on our quiet side road, it began to run rough with dark smoke coming out of the exhaust. It sounded like brrrrruup, brrrrruup, brrrrruup and acted as though it was getting fuel, then none, then fuel and then none. We put it back in our shop. Yesterday, it ran roughly again on start-up, with dark smoke, same symptoms. Then after we shut it down for 15-20 minutes, it ran smoothly again with clear exhaust. Soon, however, it was back to running roughly. Today we tried a "spare" RAKX-0, which ran roughly just like the first carburetor. We've carefully checked and re-checked valve clearances; spark looks good, and we even changed out the spark plugs from Champion C-16 to original-recommended Champion C-4. On removal, the spark plugs are found to have black carbon build-up. The curved part of the plugs looks white, so it seems the spark is good. Black carbon would be a sign of the carburetor flooding; we tried float adjustment so the float would decrease fuel input, but that was no help. The carburetor was rebuilt from the 1928 kit available from Filling Station. We changed out the needle valve, with no apparent change in the way it runs. A new distributor and rotor are installed.

Does this appear to be the carburetor, or might it be the valve clearances or something else? Is it possible an electrical component is heating up and malfunctioning? Maybe the capacitor? (Coil and capacitor were new six months ago).

Thanks - Ted

Could be a faulty float or valve in the vacuum tank allowing fuel to enter the manifold. Try and disconnect the pipe between the manifold and the tank, seal both ends and gravity feed the fuel in.

Also check your fuel lines, I had a flake of some metal once got stuck in line just before the vacuum tank and some times it stayed parallel with the tube and no issue and some times it pivoted and restricted the flow took me weeks to figure it out, Ray

(1) The vacuum valve on the vacuum tank is infamous for failing, allowing fuel to be sucked directly into the intake manifold, bypassing the carburetor.

(2) New (not new old stock) electrical components which have their origin halfway around the world (even when in a name-brand box) are infamous for failing with a little heat.

The smoke indicates either too much fuel or too little spark.

Jon.

Today I swapped out the condenser for a new one. On startup the engine ran smoothly and with clear exhaust. After 7-8 minutes it stalled and on restart acted exactly as it did previously - dark smoke and rough running. I swapped out the coil for another new one, and results were same.
I'll try the suggestions made elsewhere here, such as gravity feed without the fuel pump, and will update status within a few days.
Thanks! .... Ted

It turns out the vacuum fuel pump is the source of the problem. I disconnected it, then connected up a gallon can with gas, a hose and shut-off to the inlet line to the fuel filter. The car started right up and ran with clear exhaust and quite smoothly for more than 20 minutes. After shutting it down, it re-started and continued to run smoothly.
I think I'll opt for adapting a 6-volt fuel pump to this vehicle and not try to fix the old Stewart-Warner vacuum pump.
Thanks to Yobbo and carbking for pointing out a sensible solution.
.... Ted