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Old 04-05-2007, 03:13 PM
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Re: 94 running rough with a twist

Was the distributor cap and rotor also replaced? Were they AC Delco also? What brand of spark plugs and spark plug wires were used? Was silicone dielectric used on all secondary ignition terminals, (cap, rotor, both ends of spark plug wires)? What is the fuel pressure?

Fuel pump operation:
The fuel pump circuits are designed to energize the fuel pump continuously any time the key is in the START position. When the key is in the RUN position the fuel pump will operate provided the engine is running. If the engine stalls, or is not running for any reason, the PCM will shut off the fuel pump after approximately 2 to 3 seconds.

Fuel pressure test:
Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates a leak. The most likely place is the fuel pressure regulator, or the lines under the upper intake manifold.
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