1998 Chevy Malibu hard start, running rich

MPATTERSON

MEMBER
1998 CHEVROLET MALIBU
6 CYL
FWD
AUTOMATIC
207,000 MILES

My car starts fine when the engine is cold, but when the engine is warm, the car starts hard and the exhaust is rich. I have replaced various parts and had a complete fuel injection service replacing cylinder head, fuel filter, etc. Have replaced the MAP sensor and several other sensors. Fuel pump tests with correct pressure. Just brought my car to a professional mechanic at a Chevrolet dealer and the mechanic claims the problem is the fuel pump. Can you verify that the fuel pump would be the problem and nothing else could be causing this. I hate to spend the $800 they estimate to only find out this is not the problem. Thankyou for your help.

3 Replies

MASTERTECHTIM

MECHANIC
4,750 POSTS

What you are describing does not sound like a fuel pump problem. You said its running rich once you get it started when it is warm. About the only thing that could cause that is the fuel pressure regulator. Now a unexperienced mechanic might misdiagnose a bad regulator as a bad fuel pump. On the fuel rail on the engine, where the injectors are the regulator sits. It has a vacuum line going to it. Ill bet you if you remove the vacuum line when the car is warm, you will find gasoline in it. This is caused by a ruptured diaphram in the regulator. This is a inexpensive repair. It should cost about $100 parts and labor. I hope this helps you.