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Why am i having trouble starting when warm?
The car has a small block 351w-427R.
It starts up immediately when cold. When warm, sometimes two or three attempts with a couple of seconds of cranking, unless I catch it just right with a few pumps on the gas pedal and just enough pressure on it while I start. A new fuel pump was installed at the beginning of summer. I don't really remember having this issue before it. The mechanic says its due to the high levels of ethanol in the fuel. It took all summer, but I last week put in 5 gallons of 104 octane and filled the rest with 94 octane to see if this rectified the issue. It didn't. I've also read it could be the starter not working well when warm. Any thoughts or suggestions? |
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Do you have an electric fuel pump or mechanical? At this point my guess would be vapor lock or fuel percolation. The area around the carburetor is hot enough to vaporize the fuel. One solution is an insulating spacer between the carb and intake manifold. Electric fuel pumps seem to be less prone to this than mechanical pumps. Probably worth a few minutes to check out this thread: http://www.clubcobra.com/forums/holl...erc-issue.html |
Vapor lock on a carburatored engine? Is there a spacer or heat shield between the carb and manifold?
Larry |
On a warmed-up engine, you should only have to depress the gas pedal slightly (maybe half way at most) and turn the key (no pumping). Otherwise, you risk flooding it. If that doesn't work, then you might be boiling the fuel out of the bowls. If the starter is cranking the engine slower when warm, that could be a whole different issue (weak ground wires, thermal expansion of an older, non-high torque starter, not enough CCA from the battery, etc.).
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Had the same problem with my roush engine when new. Put a 1/2 inch phenolic spacer under the carb. Problem solved. No more percolation.
Also, during hot restarts, use no throttle. Should fire right up. |
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If the starter is cranking quick when warm it's not your starter. |
By all of the replies so far, your starter sounds fine.
What carburetor have you got? Photos would be good. |
99.9%....... you need a spacer between your carb and intake. Had to put one on my old Roush 427R.... problem solved. Just make sure your air cleaner will still clear the hood if you install one.
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Had the same problem with my 1955 Thunderbird, which was livable for many years. When I had to switch to 10-15% ethanol the problem became even worse. Replaced the carb with a new Edelbrock, new phenolic base plate and blocked the manifold choke heat riser passageway. Never really fixed the problem. Sold the car soon after. My ERA has a turkey pan which I feel reflects the heat from the engine and the carb.
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After its warmed up, if it is turning over slower compared to when cold, your timing is to far advanced. Could be vapor lock could be heat soaking...
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Aluminum intake, aluminum carb, definitely needs a phenolic spacer. Mine was boiling the fuel out of the bowls and giving me all sorts of problems. Cheap little spacer solved it. And Jeff Classic adding a whole bunch of timing really woke her up.
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You only need one metal heat shield and two gaskets. Bill S. |
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Thanks all for replies. |
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Just get one on there, you'll notice the difference. Gary |
I may be missing something ?
If you overheat a starter it will not give full crank. I replaced my starter and added a stick on heat shield. Two years no issue. |
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Bill S. |
Good one Bill........
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Cheers, Glen |
Vapour lock: How to cure
It seems clear you need to try the spacer idea, as its simple and clearly other guys say it works.. However, if that doesn't solve it, then it means your near static fuel is most likely boiling in the line to the carb, once the engine is shut down. When it boils, AKA Vapour Lock, it creates an air pocket that can in effect, stop fuel getting to the carb.
One way to overcome, is to set your bonnet open slightly and alter your radiator fan, so it stays on longer after shutdown. Renault did this with the little 5 Turbo and it cured the hot start issues, which originated from a sometimes red hot turbocharger. However, the bulletproof method is to have a return line back to the tank from the carb, with an in line regulator. This way cool fuel from tank is constantly circulating at idle and can't boil. As with all fuel line fittings, monitor tightness regularly as failure of these is what causes engine fires. Metal air filter elements are better too. |
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