Checking volts with a meter will not tell you what the voltage is under load - are you checking it when just sitting or while cranking?

If you are saying that it cranks faster when you jump it than when you are just trying to start it normally, but before you have drained it down to the point of needing a jump then the battery is weak. Maybe it is not even the right kind as these cars use a BIG battery. Just the fact that you got it started with a jump tells me it is probably contributing to your problems.

I bought a Bosch battery at Pep Boys for my '79 and I think it was 1000 CCAmps. Is your battery bigger than any other car battery you have ever seen? I'd suggest you get a new one and make sure it is one of those big mommas. They are only around $100 and if yours is already 3+ years old you will need one sooner or later.

If that port on the IP is open and clear I think you could probably test it but I don't recall how...for now just make sure it isn't clogged with dirt and take care of the battery.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz