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MG MGB Technical - Hot fuel

It has been over 100°F in the Land of Enchantment the past couple of weeks and the B has been suffering.

My car has A/C, which works well, but introduces extra heat to the engine compartment. The car reaches a certain temperature after driving and stopping for lights where idle becomes very dicey. I can keep it slightly accelerated with the choke fast idle or with the foot but the car will die or barely advance once the light turns green. Under such conditions, there is often rapid clicking of the S.U fuel pump until the car is moving along again.

The question is whether or not it would help to insulate the carburetor bowls, hot spots in the fuel line and perhaps the fuel handling portion of the fuel pump. The problem is related to the alcohol added to fuel in the U.S. In Mexico, the car remains stable even in intense heat.

Any suggestions as to how and where to deflect heat or insulate against it would be helpful. I suspect the problem is in the carburetor bowls but the fuel pump may be taking excessive heat from black pavement while stopped and idling.

The U.S. emission controlled version of the MG-C had a squirrel cage fan and ducted air from the front of the car to the carb bowls. A fuse box fan from a modern German car might serve to blow air onto the bowls if this is where the problem is.
Glenn Mallory

Glenn - "MG-C had a squirrel cage fan and ducted air from the front of the car to the carb bowls."
The MGA people have used a small bilge blower to blow directly onto the carburetors to prevent the situation that you are experiencing. The blower can be turned on and off with a switch, or you can get a temperature control circuit from Rainbow Kits at: http://www.rainbowkits.com/ that will turn the blower on and off through a relay when the temperature gets too high.
Cheers,
DW DuBois

The rapid clicking could be the pump failing to pick fuel up from the tank. If there is liquid fuel there, then unless it is evaporating in the lines to the front and the carbs faster than the engine is using fuel, the pump should only click at the normal rate. You can check which end is the problem by getting the problem somewhere you can stop safely, and lifting the bonnet, which of course should lower the temperatures in the engine compartment.

The carbs are normally colder than the air surrounding them as they are evaporating liquid fuel, and so acting as one half of a refrigerator. Trial wrapping the float bowls may also indicate something useful.

The idle can get rough with very high underbonnet temperatures, as the mixture can be compromised by the temperature of the air as well as the fuel. Are these HS or HIF? HS have exposed jet pipes so can suffer the effects of heat more than HIF. They are also more likely to suffer from rough running in high heat than HIF as HIF have temperature compensated jets.

paulh4

This thread was discussed on 25/06/2016

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