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The Fife · Joined: 17 Mar 2004 Posts: 241 Location: San Antonio, Texas

edit: See my 3rd post for latest info.

Well the engine is finally back together and I think the car is ready to go. I could only crank it over a couple of times (maybe 15 seconds total) before the battery wouldn't turn it over anymore. I guess the gas couldn't get up the lines by then. The battery has been sitting, unplugged in the car for the last 2 1/2 months and it's on the charger tonight. Hopefully things will work tomorrow. I'm sure that's about all I'll be able to think about tomorrow at work!

The Fife · Joined: 17 Mar 2004 Posts: 241 Location: San Antonio, Texas

Looks like I have a different problem on my hands now. The starter won't turn (lights dim and I get clicking). Normally I'd think that it's a battery, cable, or ground problem but the battery tested normal and I cleaned all the battery cable and starter grounds. The starter is off and I'm testing it later. Sooner or later, this engine will start!

Porschephile · Joined: 04 Nov 2002 Posts: 825 Location: Denver, Colorado

I had something like that when I rebuilt my engine. did you make sure to propperly set the engine speed sensors in the flywheel? if they're too close, it'll throw off the tach. if it's touching, consider it f*cked.

I didn't realize about the gapping, so I had it touching (unknowingly) and it tore off the sensor and jammed it in the flywheel. no matter how much cranking the starter wanted to do, the engine was jammed. My porsche tech made quick work of it.

Check it out...I bet you could do it yourself. I just didn't feel like diagnosing. shipped it off, $1,000.00 later, yeah.
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werd B.

The Fife · Joined: 17 Mar 2004 Posts: 241 Location: San Antonio, Texas

I never had the engine torn down that much - just the head, intake, exhaust, water pump, and anything else that had to come off to get down to that stuff was removed. So I'm hoping those sensors are still allright. Here's what I know so far:

- The starter is ok - took it to AutoZone and it spun right up.
- The battery is ok - that was tested today and it has a full charge.
- The cables at the battery are in great shape. The two smaller wires coming off the positive cable don't look as clean as the main terminal connector though. I'll clean it up and see if that makes a difference tomorrow afternoon.
- The cables on the back of the starter are clean.
- I get 0 resistance between the neg. battery cable and anywhere on the engine (the battery is unplugged when I do this!).

Symptoms: When I turn the key to 'start' all I get is clicking and the lights dim. This sounds like a bad ground somewhere? Which one(s) are likely suspects here? Maybe the infamous one at the rear of the engine?

Sleykin · Posted: Thu Oct 21, 2004 1:39 pm Post subject:

Put a voltmeter across the battery when you crank it. If the voltage drops to less than 9 volts you have a bad battery or too high a current drain from a starter problem. If the voltage does not drop more than 1 volt (11 volts) then you have a bad connection someplace. Normally battery voltage drops to 9-11 volts when you crank the starter. If you have just a small drop indicating a bad connection...measure from the + battery terminal to the starter input post. You should see less than .25 volt when you crank. Do the same from - post to engine block. You can't measure resistance this low with an ohmmeter (unless you have a very expensive microohmmeter) The lead with the highest voltage across the lead is the one with the bad connection. Your starter or solenoid could still be bad unless it was tested under load.
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Glenn Neff
Medford, OR
87' 924S

The Fife · Joined: 17 Mar 2004 Posts: 241 Location: San Antonio, Texas

The starter wasn't tested under load - just on the bench.

I'll have to try and scare up some help this afternoon for this (I live alone). The starter input post is the small one? My multimeter and its wires aren't very big - will measuring the voltage across the battery put a huge load on it? I'd hate to fry the thing.

Sleykin · Posted: Fri Oct 22, 2004 1:17 pm Post subject:

Nope it is the big terminal and you will be measuring very small voltages. Just don't put the meter in current mode and put it across the battery or you will blow the intenrals of the meter (fuse) ...
You are measuring the IR drop of the wire. If you knew exactly how much current the starter was drawing you would be able to calculate the resistance of the wire and connections. E=IR R=E/I So my .25 volt cutoff would give you .0025 ohms at 100 amps. That dosen't sound like much but if you calculate the power that is about half what it would be if you had a headlight in series with the starter about 25 watts. Consider that the starter is drawing 100 amps at about 10 volts and you see that is 25% of the power the starter needs to start.
Point being that very small resistance in the wires and connections have a very great effect at high current and low voltage.
Hope that helps.
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Glenn Neff
Medford, OR
87' 924S

The Fife · Joined: 17 Mar 2004 Posts: 241 Location: San Antonio, Texas

That helps out a lot! It's been a little too long since I took those engineering electronics classes.

I still haven't been able to find an accomplice to help out so I just fooled around some more with the neg. ground. Turns out that's the problem. Much cheaper to fix than replacing the starter!