Engine chokes and even stops when I step on the gas
Thanks for all your interesting videos from Tokyo, Japan. I am learning a lot from you.
My only car for the last 7 years has been a Mercedes 280S Sedan (W108 chassis with M130.016 naturally aspirated inline 6 engine, automatic transmission, has about 125,000 KM now) from 1971. I used to be a gear head in my younger days when I used to ride on different motorcycles, but when I quit riding bikes, I have totally given up that hobby and have been riding latest cars and left maintenance up to the dealership. That all changed when I purchased this Mercedes, which was a dream car for me for many years.
Since I acquired this car, I have been proactively changing different parts such as water pump, brake booster, carburetors, coolant hoses, engine and transmission mounts, alternator, wiring harness, a/c system, brake hoses, drag bars, steering damper, subframe mounts, etc. I also rebuilt the brake calipers, power steering pump and steering gear box. I replaced the mechanical fuel pump with Carter's electric pump and put a return type fuel regulator to keep the fuel cycling through all the time to keep the fuel system cool. The exhaust at one point became too smoky, but replacing the valve stem seals fixed that. The engine was quite clanky but adjusting the valve clearance totally fixed that. The car never died on me and I really enjoy driving it. As most work had been done by me with some help from a friend mechanic, the maintenance cost had been minimal so far. I purchased a used tranny which only had about 10,000 KM on it and had it totally rebuilt for about $2500 recently, which I plan to install soon, as the current transmission is a bit leaky around the shaft and gradually starting to slip, especially when I am accelerating on a freeway.
One issue I have with the car is when I step on the gas on a hot day when the car had been in idle for over 10 minutes or hitting the road after restarting after parking for up to 30 minutes or so, not enough for the engine to cool down. The engine chokes and sometimes even stops unless I step on the gas very very slowly. This goes away after driving for a 5 to 10 minutes and the coolant temperature goes down to about 85 degrees centigrade. I do see that the oil pressure drops on idle when the coolant temperature goes up to about 90 degrees centigrade. (I use either Chevron or Valvoline 20w50 mineral oil.) I replaced the carbs from Zenith INAT 35/40 to Weber 38/38, as the Zenith carbs kept on giving me air leak at idle when they got hot. I tried rebuilding the Zeniths but had far too many woes and just gave up. The mixture screws had been adjusted and seems to be fine, as the spark plugs don't get that dirty. The acceleration pump seems to be squirting enough fuel too. What could the problem be? The only thing I haven't adjusted is the float level. Thanks for you help.
Well certainly could be the float level just realized carburetors are always the problem in old cars like that if you can find an old mechanic like me who really knows how to work on those you might have them rebuild them and then adjust them with the gauge not just by ear using an actual flow gauge
The float level is a pretty critical adjustment on carbs. So is the accelerator pump output, it needs to be properly measured. Idle mixture screws, idle jets all have to be correct to function properly.
When I got a Weber 32/32 specifically for my 22R, the idles and main jets were completely wrong and there was a small cotter pin stuck down one of the emulsion tubes. The float levels were also, way off. I guess they made it on a Monday morning. I had to buy a jet kit to get it right.
Thanks, Chuck. In this "modern" age of debatable engineering progress I forgot all about good old vapor lock.