The alternator is new, 2wks old. I measured the battery without turning key on, is 12.62V; with the key at ON position, it is 12.02V. I would imagine as I start cranking the engine, the voltage will drop until the engine is started. But shouldn't the fuel pump works for a couple of seconds when the key is at ON? Can I just plug a power supply at 12V to verify if the fuel pump is working or not?
This is barbaric I will admit, but take a rubber mallet and hit the top of the fuel pump cover. If the pump turns on, well then you know you need a new pump. Your batt is fine, so is your alternator. Have you been able to locate the fuel pump relay? If you do, give that a gentle tap as well, sometimes as the relays go bad they start to stick. I'm not sure what the voltage to the fuel pump is suppose to be, but it should be turning on with the voltage you listed. Unless for whatever reason it is only allowed to run with 12v.
But seriously just give it a whack, worked on my Volvo and I was able to get home. That car also ended up years later having a bad fuel pump relay. A whack to that got it up and running more than once till the new one arrived.
< Message edited by Jeffla -- 12/2/2007 9:40:02 AM >
Thanks Jeffla, I tried to whack it with a rubber hammer, it did not change anything. As far as I know, the cap does not have a rigid connection to the fuel pump so I am not sure whether my hammering can have effect on the pump. I have not been able to locate which one is the fuel pump relay yet although I have access to the relay panel now.
I have measured the voltage on the fuse, it is 4.17V with the key at ON position. Can someone please tell me if this is the correct reading? Shouldn't it go up to 12V for a few seconds for the fuel pump to charge the system and then come down?
Your relay is working if you are getting 10.?? volts at the pump while cranking. If the relay was bad, you will get 0 voltage to the pump. Your pump is bad. The fuse for the pump is #28 and the relay is #372.
I used an external power to connect to the fuel pump, and it worked. I put the car connector back, had my wife crank the engine (not just the ON position), there was fuel coming out from the feed line. I then used the external power again to run the fuel pump for about 10 seconds to charge the feed line with pressure, used another car to jump (so that the battery is not a concern), it still wouldn't start. I know I have sparks, I have fuel in the feed line, I have RPM reading from the ECM, my starter cranks, the car just does not start.
Tomorrow, I will have a friend come over to go through the basics again just to make sure I did not make any incorrect judgement. But I do have a question for now on the starter:
1) what is the RPM supposed to be when the starter starts the engine? 2) As far as I know, a starter does not just stop working; it should show sign of going dead but actually go dead slowly; this happened to a car I used to have. But as long as it still cranks, it is only a matter of "harder to start", right?
Do you by chance have a 2.8? They have issues with carbon buildup. If so attempt to start the car with the gas pedal to the floor. It may take extened cranking to get it to start. 100-200 rpmp should be plenty to get the car to start. The factp tat your getting fuel and spark is a good indication of that. If rpms arent sufficient you wont get either. You may also want to check for incorrect coolant temp sensor readings. If you have a scan tool your can compare the coolant temp to the air temp to see if they are reading correctly.
Thanks Dankhound. Problem solved. Mine is a 99 A6 2.8. I made a wrong judgement on the spark plug when this issue first came up. It is actually wet instead of dry. I guess the tip of the spark plug will always be dry; the thread area is wet I later realized.
I did what you said, gas pedal to the floor, the second attempt the car started and lots of smoke came out. What happened before this issue was that the morning before I started the car, the engine went to high RPM, I moved the car from my drive way to my garage, and shut it off while the engine was still in high RPM. The whole process lasted about 10 seconds, and I think that's how I flooded the engine.
Dankhound, you said the carbon buildup, I used SeaFoam 2wks ago, it is supposed to remove the carbon build up, or is it? And did you mean the carbon buildup at fuel injector so it does not close well causing the engine flooded?
Also, thanks a lot to Jeffla and AudiTech79 for providing valuable advises that helped me to identify the root cause!
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RE: car won't start - 
