Post-War Other Renown - Idle too fast

Hi Everyone:

I have a '51 Renown that is idling too fast. It has the Solex Type 32 B.IO carb. The fuel pump has been replaced with an electric model (BTW: Does anyone know what the fuel pressure should be?). The idle screw is all the way out and the butterfly looks to be closed. The problem exists at any temperature or choke position. Any ideas?

Thanks!

Hal - welcome to BCF.

Uncontrolled idle speed is often due to vacuum leak(s).

Do you know how to troubleshoot vacuum issues?

Tom M.

NutmegCT said:

Hal - welcome to BCF.

Uncontrolled idle speed is often due to vacuum leak(s).

Do you know how to troubleshoot vacuum issues?

Tom M.

Click to expand...

Thanks for the quick reply. I did not realize that this could be a problem with a car this old. How do you suggest that I proceed to diagnose it?

Other than eyeballing areas around the carburetor, you can spray a mist of water around the manifold and where the carb joins the manifold.

When the engine slows down, you know that's the area where the water was sucked into the manifold.

On my old 1960 Mercedes-Benz 190b, the flange between the intake manifold and carburetor was actually warped, probably due to heat. Air was sucked in throwing the mixture off and speeding up the engine. I replaced the flange, and trued the bottom of the carburetor (lapping). Problem solved.

Hope this helps.
Tom M.

Sounds simple enough. I will give it a try in the morning. Thanks.

I couldn't find the book just now, but ISTR the Solex downdraft on my Sports 6 only wanted 2-3 psi; just like the later SU carbs. But excess fuel isn't likely to make it idle too fast; instead you'd be seeing black smoke and perhaps a rhythmic miss.

So look for any source of excess air (or fuel/air mixture) getting in. In addition to the usual external leak points, check for a badly worn throttle shaft and, if you can't find anything else, whether the throttle disc fits the bore snugly.

Also might be worth putting a timing light on it, to make sure the timing is reasonable. I've seen several distributors where the advance springs are simply missing, which means it flops to full advance as soon as the engine starts.