2003 Mercury Sable. 24v V-6.
Question: Hi, recently had badly corroded positive battery cable. I replaced it and my car started. Two days later it wouldn't turn over. Replaced battery and then it as fine. Now my car intermittently shuts off. What could the problem be?
Car turns over fine but will not start. Has been taken to the Ford repair garage and the mechanic couldn't find a problem. It is currently at another repair shop. There is no fuel to the system. However, car sets for 10 mins and will start right up. May run for a day or two then shuts off and again no fuel. Garage is baffled as it is an intermittent problem. Possible that weak battery caused a computer problem? Any help would be great. Tim.
Answer: Hi Tim. Start with a scan of the computer codes on your Ford even if the check engine light is not on. History codes may be stored in the PCM memory. Does the engine have spark when there is also no gas? The cranking problem has seemed to be fixed with the battery and cable replacement you did. Stalling out when driving then not starting back up due to no fuel pressure could be caused by several things. Possibly just a coincidence that the fuel pump is failing. Testing at the pump connector for power and ground would be needed when there is no fuel pressure. If there is power and a good ground, then the pump is bad. Have seen had them act this way and cause the problem you are having.
Next time you have this no start condition have a fuel pressure gauge on the engine port to verify low or nor pressure. listen for the hum of the fuel pump hen you turn the key to the "ON" position. You should here it come on for 2 seconds or so then shuts off. If not then have someone under the car and bang on the bottom of the fuel tank with the palm on the hand or use a rubber mallet. If the fuel pressure comes up or the car starts then the pump is bad in your Sable.
If there is good fuel pressure but no injector pulse to spray the gas into the engine, then this is a different problem. You would need what is called a Noid light plugged into an injector electrical connector to check for signal pulsing when you crank it over. You can also use a normal test light. If there is no pulse then there is a possible computer problem, sensor problem, etc. If you jump started your Mercury Sable because of the cable and battery problem, this could have damaged the computer, but it should just be totally dead.
It is also possible that you may have knocked or damaged a sensor or wiring connector when installing the cable. Another odd thing i have seen on different cars is a positive cable routed too close to- say a crankshaft position sensor, causing an erratic reading. This would cause no fuel pressure AND spark since the computer is confused about engine RPM. Again, you need to find out if there is spark when it stalls, and is there power to the fuel pump and are the injectors spraying. This is one of those problems where testing the different systems while it is acting up will be the only way to fix it. Guessing at parts and sensors will get very expensive.
