Questions and Answers

Astro Running Rich Q. I have a 1994 Chevy Astro VIN series W, with a 4.3 litre Vortec 6 cylinder engine. The engine has 130,000 miles on it and is Central Port Fuel Injection. The problem I am having is with the fuel mixture running rich, leaving carbon deposits on the tailpipe and causing a sulfur smell from the catalytic converter.

The engine is also hard to start when cold and idles rough until after the engine has warmed up. I have changed the plugs, plug wires, distributor cap and fuel pump within the last 6 months, several months before this problem started. I suspect that the fuel injector/regulator maybe defective and allowing to much gas into the fuel mixture. Is there a way to verify this? Do you have any other (cheaper) suggestion to try before I replace this unit?

Thanks for your help,
Fred

A. First thing you will need to do is check the fuel pressure. Hook up a fuel pressure gauge to the test port on the injector feed rail and start the engine. Fuel pressure should be 55-61 psi at idle. If it is higher than that, then the fuel pressure regulator is bad. If it is normal, then the injectors are the most likely problem.

With the engine shut off, clamp off the fuel feed and return lines. This will isolate the injectors. If the fuel pressure drops, you have a leaking injector or injectors.

There could be other reasons why the engine is running rich also. You could have a bad Coolant Temperature sensor or O2 sensor. If the fuel pressure test checks out, then we have to look elsewhere for the problem.

Additional Information provided courtesy of ALLDATA