Rochester 2 Jet Loses Power

carburetor Mike

Here is a question I got from one of my customers.

My Rochester 2 jet Has a stumble when pulling away from a light or stop sign. I purchased a accelerator pump and power valve from you. I thoroughly cleaned the carburetor and replaced those items. Now with the engine turned off I have a great pump stream. But if the car is running no pump stream. Turn the motor off and great pump stream again. Any advice on this would be appreciated!

I assume that when you say you get a good stream when the engine is off that you are pumping the throttle and watching the accelerator stream out of the main discharge. What comes to mind 1st is the main discharge and the check ball. Be sure the larger check ball is placed in the main discharge hole, then the copper colored spring, then the T.

The more likely suspect is that there is low fuel in the float bowl and the engine when running is using up most of the fuel and there isn’t enough to run over into the accelerator pump well. This could happen to the type 2 Jet that doesn’t use a check ball and feeds itself over the side of the well through the slit.

The 1st thing to do is make sure the float is set to factory specifications. While doing this use some teflon thread paste (NO tape) on the needle’s seat threads and wipe the viton needle tip with some no residual spray, or mineral spirits.

Another possibility is a bad fuel pump or some other impediment to fuel delivery. Check the fuel pressure of the fuel pump and make sure it is within factory specifications.
From my friend Jeff “Do you tell all of your customers (as I do) to use only fuel-injection-grade fuel hose (SAE 30 R9) or Gates Barricade hose?  This saves me a lot of complaints as internally-collapsing R6 or R7 hose is often miss-diagnosed as a carburetor or fuel pump problem; it is due to — what else — ethanol damage.”
So there you go, some possible remedy to a rather peculiar problem.

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