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    Teresaz1's Avatar
    Teresaz1 Posts: 2, Reputation: 1
    New Member
    		  
    #1

    Mar 4, 2015, 07:10 PM
    02 audi a6 quattro intermittently doesn't start
    Intermittently doesn't start after turning off engine and attempting to restart after about 10 minutes.

    Seems to need wait at least 1/2 hr or longer to restart depending on exterior temperature.

    No engine light or codes.
    Not over heating.
    Changed gas cap (new)
    Cranks fine.

    Could it be the fuel pump?
    Different mechanics cant diagnose it

    All else is fine. Car is great on the road
    odinn7's Avatar
    odinn7 Posts: 7,691, Reputation: 1547
    Entomology Expert
    		  
    #2

    Mar 4, 2015, 07:24 PM
    You need to first determine if it is a spark or a fuel issue.

    It could be the fuel pump but is it? No way to know without checking it first. Next time it happens, you will need to find out if it is getting fuel or not and then whether or not it has spark.
    TxGreaseMonkey's Avatar
    TxGreaseMonkey Posts: 16,761, Reputation: 5597
    Uber Member
    		  
    #3

    Mar 4, 2015, 08:49 PM
    It could be something as simple as replacing the Crankshaft Position Sensor or the Camshaft Position Sensor. I've seen intermittent failure in these sensors that did not throw a code. MAF Sensors are very sensitive on some vehicles and can present perplexing problems. I would attach an advanced scan tool and check for pending codes--it may give you an edge in assessing the situation.

    It goes without saying that you want to ensure the ignition system is in great shape; i.e., plugs, wires, and coils. 90%+ of all crank but won't start situations are electrical related.
    CaptainRich's Avatar
    CaptainRich Posts: 4,492, Reputation: 537
    Cars & Trucks Expert
    		  
    #4

    Mar 5, 2015, 06:15 AM
    To determine if the fuel pump is the culprit, attach a fuel pressure gauge and monitor fuel pressure when the 'no start' occurs. Fuel pumps can overheat even inside the tank and lead to an extended crank time before the engine finally 'catches' and runs.
    Most cars won't store a code when the fuel pump fails like this.
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