Amber Gramps

I'll ohm test it first, but then saturday the thing's going up on jacks for more cleaning anyway, so.....what's one more look see?

Honestly, if we don't resolve it this week I ain't gonna sweat it. I leave for Kona in about a 12 days.

Amber Gramps

Senders ohm out within spec.

The local parts counter gave me my money back on the new coil.

Did I mention it's hot out?

Amber Gramps

Parking the following link for later review.

http://forums.pelicanparts.com/porsc...ml#post3749067

rusnak

Hey DB, not sure if you've already done it, but you might have your battery tested under load. It is possible to crank the starter over even with one bad cell, but not have enough voltage to open the injectors, especially if you have a big battery.

User 4221

The same goes for the ignition.... Too much current to the starter and not enough to the coil.

rusnak

Scott, can you explain that? For example, what would cause that to happen? You mean a starter that is drawing too many amps?

User 4221

Assuming the starter is OK, a weak battery can do some weird things. I suppose a failing starter can do something similar but this is not too likely.

As an example: If the battery is weak and can only supply, say, 100 amps, and the starter requires, say, 90 amps, there is not much current left to drive the coil and other consumers (like injectors) during cranking.

A weak battery can also "bounce". Meaning, under load it can provide surge current that may exceed the starter's demand and supply enough current to drive the starter and coil (or other devices)

Another test is to turn on the interior lights and start the car. If they dim significantly, then a weak battery is suspect. If they don't dim too much, then you can probably look elsewhere.

I'm a much better hands-on troubleshooter than internet troubleshooter. Perhaps Loren will chime in and tell me how wrong I am

Amber Gramps

Thanks Scott and rusnak, The battery is an Interstate OE replacement that is fully charged.

I took the DME apart tonight and looked at it long and hard under a very nice magnifying glass. I can see nothing wrong with either side of either board.

I've been playing with it for days now and have a slightly different take on the situation. Now it seems to almost never fire on the first turn of the key. On the second turn it will almost always fire very strong no matter how long I leave it in the "on" position prior to hitting "start"...

I'm back on the idea that the crank position sender is too old and too far from the flywheel.

rusnak

A quick way to test it is to plug a second one into the dme harness, and crank the engine while pulsing the sensor against a metal object. If you want, I can send you one of my old ones. It's actuall really easy to re-set the gap with a small washer and some silicone glue on an old sensor.

Amber Gramps

I may take you up on this. Was a little confused at the process of replacing the sensor....is it a drop the motor or tranny kinda job? I gotta pay more attention, focus, and actually do something to fix the problem. I want to work on it, but am so dang distracted that I'm lost even worse than normal.

sending PM

Lorenfb

"At 12.4 your starter will spin, but the injectors won't open because they will be barely getting 12v."

- rusnak -

That's not correct. The DME ECM will function at minimum at 8.0 volts
which one would expect from an OEM ECM design. What kind of a
Mickey Mouse ECM would be integrated into a vehicle that would
crap-out at 12 volts under a cold cranking condition.

But then again: Maybe Porsche did do that and most of the Porsche
dealers removed the Porsche warning sticker; "Avoid trips to Mammoth
Mountain during the weather months with this vehicle", right?

Amber Gramps

Loren, as much as it pains me, and only because you entered the thread on your own, I'm gonna ask what you would do?

The car almost never starts on the first turn of the key. The car almost always starts on the second turn of the key. She has fuel. The coil isn't providing spark. What would you do?

User 4221

Have you looked at the Cayenne's Body Control Module? It will do this at ~12V and not let the vehicle start..... and flash air suspension warnings.... and airbag warnings...

Lorenfb

Two very simple tests to localize the problem:

1. Remove the coil wire from the distributor cap and
place the end about 10mm from the engine case.

2. Remove the #1 injector connector and insert a noid light,
buy one at AutoZone/Reillys or Pep Boys.

3. Have someone crank the engine while you monitor both
the coil wire & noid light.

Tests results:

1. Both immediate spark and noid upon cranking then;
Both speed & ref sensors, powers/grounds O.K., and
DME ECM O.K. - Check for fuel pressure and/or spray
carb cleaner into air filter and re-do steps 1-3 above.
Check distributor cap next.

2. If neither noid nor spark then; check sensors, DME ECM,
or powers/grounds, or DME relay

3. If noid but no spark then; DME ECM a problem,
or power to coil from ignition switch (since already
replaced the coil), also check coil wire for resistance.
Once it starts, remove the ref sensor connector, the
engine should keep running and accel perfectly if
not then bad speed sensor. Next, try reversing the
speed & ref sensors on the engine and then the
two connectors on top, i.e. Possible weak sensor.

4. If spark but no noid then; power connection to
injectors or bad DME Relay.

The above is a starting point and NOT an exhaustive/in-detail
troubleshooting guide.

Amber Gramps

Thank you Loren. My son will be home tomorrow to help with the list. I've had a heck of a time trying to hold the light and turn the key at the same time.