Hi. I have a 250 with an RBS carburetor, 800 idle, 12° timing, ported advance, manual choke. Cold start is fine I give it a couple of pumps and it starts right up and hold my foot on the gas at about 10-1100 rpm to warm, push choke in, fine, idles ok drives ok, runs cool... If I park and then go to start again after a while , and now in warm weather, will only start with gas pedal fully depressed and held down and then turns over after a few tries, but with high rpm which I immediately bring down and again everything is fine. Carburetor seems to want a lot of air, iidle air mixture 3+ turns out, vacuum steady at about 19in. So any advice on restarts in warm weather, or maybe all that I have said seems normal, would be greatly appreciated. Thanks.
All Small Six 250 Warm start info?
- Thread starter edcom
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I'll give that a try, thanks. The carb isn't right on the manifold it's on a block about 5/8" but not the one where the coolant runs through it. Didn't think it was hot enough yet for vapor lock yet but yeah maybe some quicker evaporation? I'll give it a try and let you know. Thanks again.
The dreaded hot-soak flooding. Lowering the float may help- but it may not. The solid steel lines running over a hot engine quickly take fuel to boiling temps. There can be double-digit pressure in the static line, and no needle can hold it back. While the engine is off, it's slowly flooding itself.
Insulate fuel lines is a risk free place to start. It does help for sure.
Hi - interesting and well reasoned and an easy enough remedy! I'll certainly give it a try. Actually just today, an 80+ degree day here in the Northeast, just minutes after turning off the engine I used a handheld temp reader and pointed it at different places on the engine, I have 180° thermostat in it and as I said in the original post the car runs relatively cool when driving or stopped at a light or slow moving traffic... everything fine, so when I took the readings - aluminum radiator already cooling down 160-170 degrees, head still up around 180 - 190 - seemingly rising, and block was way up there 210 - 220+. So yeah there's still a lot of heat coming up. I'll let you know how it works out.
So if I may go a little on/off point...As I said I'm on ported vacuum so when starting the car, whether with manual or automatic choke, you're still giving some amount of fuel - opening the throttle plate which is allowing some amount of vacuum to possibly have some effect on the vacuum advance - which would be advancing the timing further depending upon how much you're stepping on the gas pedal. So I guess I'm asking could this advancing in itself cause a harder starting condition?
No sir, there is not enough vacuum while cranking to activate the ignition advance. The cause of the issue is hot-soak flooding. Most carbs do it to some degree. Back in the day new cars had "proper starting procedure" attached to the sun visor. cold: Pump and release fully. ((Holding the pedal down at all on a cold start eliminates the high-idle feature. If the carb linkage is correct, press the pedal slightly, pull choke to full. release pedal then crank up. Immediately push choke in some. If the carb linkage is right the engine will hold itself at high idle. Anytime the pedal is pushed, the high idle is released.)) Warm engine, press and hold pedal 1/2-3/4 depressed and crank. So you are using the correct method for starting a flooded engine- hold the pedal down, don't pump it and crank till it fires and clears. Of course reducing or eliminating the hot soak flooding is better. Wasted gas and gas-dilution of the oil.
Gas begins boiling @ 130*F.
Hi Frank - thank you very much for such useful information! Will get to work on it right away.
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