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Posted by: Scott-thundercat Feb 21 2007, 12:15 AM

so today was a bad porsche day. drove to school this morning, then on the way to work, the car backfired twice in quick succesion and died. checked the fuel pump- worked good, checked the dwell (have a dwell meter built into my voltmeter), showed points open- take off the cap and rotor- points are open from wear... also massive corrosion on contacts... hmmm wasnt there 2 weeks ago... so i throw my spare borg warner set on- set the dwell drive for a few blocks to a guy's shop i know to borrow a wrench to set the timing as it is way retarded (dwell wasnt in same place as before) pull in lots of oil smoke.... hmmm. someone says "youre car's on fire" thinking it's just the smoke look under car- some oil on the heat exchanger is burning! run inside get an extinguisher put it out- no harm done no wires burned or anything! adjust timing- get engine running good- drive to get on freeway- works great- get on freeway starts backfiring and popping- pull off at next offramp- check dwell went from 48 degrees to 20 degrees.... hmmm? check points- big burned looking residue in a disc from points contacts all around inside dizzy for about 2 cm... wtf? take points out check them- appear good, clean off this residue put em back on... set dwell again- (this is a real fun guess and check process btw!!)

start up- car runs great... for 1 minute- dies. check dwell- points open. open cap- points burned about 1/4 away (brand new!! ) also they are hot to touch... check voltage to coil- 10.5 i belive it was with car off. my understanding is no balast resistor needed- shouldnt be too much voltage... decide might as well try again- same result this time entire point contact on arm burned off and melted the little wire that goes to condensor when it touched it briefly. tachometer jumps around when it backfires- so thinking eliminate problems- remove tach wire on coil- no help... walk to kragen 1 mile away get new points and condensor install thinking good to go. set dwell. runs perfectly. let it idle for a few minutes eyeballing dwell- 49 degrees. sweet. drive onto freeway- car dies after backfiring. exit freeway after adjusting dwell again- park car.

after parking car try to roll up window- window wont move even though roller moves through it's range. pull off door panel, push window up. close door. leave car. get perplexed.


any ideas? i am totally stumped here. cant think how 10.5 volts would fry points. also checked voltage at battery while running- 13.5 volts.

Posted by: boxstr Feb 21 2007, 12:19 AM

Did you change the condensor when you changed the points?? Try it.
CCL

Posted by: Twystd1 Feb 21 2007, 12:35 AM

Yea.... Possibly condenser.

OR:
Sounds like a capacitor... But you replaced it.... Hmmmmm

Another Possibility.

Your coil is pushing too much current to the points.

Do the standard coil test for impedance. (ohms) With an ohm meter.

The test procedure is in your manual or at Pelican technical archives.

Just thinking out loud here.....

For some weird reason my brain is saying it's a grounding issue somewhere. But I can't think how or why....

Crusty should be along with the right answer pretty soon......

C

Posted by: Scott-thundercat Feb 21 2007, 12:51 AM

mired amongst that crap i typed yes i did- both when i first got the car and today...

new condensor on both times. i also recently replaced the coil with one from summit racing... it ran great for the last 500 miles with no points issues- so i cant see the coil changing to suddenly firing hotter and killling my points 3 times today within minutes...

Posted by: McMark Feb 21 2007, 12:58 AM

Poor distributor advance plate to distributor body ground is my random guess. Add a ground wire from the points lock down screw to the distributor body and see if that helps. Don't get sucked into the 'it used to work' trap. Check everything. Assume nothing.

Posted by: Scott-thundercat Feb 21 2007, 01:06 AM

i could buy the ground thing- i was kind of thinking along those lines... i'll try it. hopefully someone comes along and says "fool you need a balast resistor and god himself removed your old one! here's where it goes" or something else... thanks for all the help so far guys! it seems i post here every other week.

Posted by: drive-ability Feb 21 2007, 01:31 AM

I look at points as if they were a toggle switch, Ask your self "why would it melt the switch"?


1. Shorted coil, amperage load too high for points handle.
2. Too much system voltage, 10.5 may be a volt too high, but not likely

Thinking out-loud

Posted by: Twystd1 Feb 21 2007, 02:03 AM

OOOps..

Double post

Posted by: messix Feb 21 2007, 02:10 AM

check the coil to dizzy spark wire. to high resistance could cause very high coil current till the spark jumps the gap.

Posted by: pin31 Feb 21 2007, 07:38 AM

Check resistance (<1 ohm)of the two wires from the relay board 12 pin connector (T12 pin 5 blk/pur and pin 7 blk) to coil.

The pin 5 wire might be melted to another wire in the harness.

Posted by: Scott-thundercat Feb 21 2007, 10:00 PM

well went back today, 12.5 volts at coil when running- everything else seemed to check out- still had issue. so i went to summit racing (got to love living in reno!) and bought a pertronix unit for it- followed mfr's instructions and installed it- btw the coil i was running only had 1.1 ohms of resistance- pertronix needed at least 3 so i went to kragen and got a niefhoff factory replacement coil- 3.5 ohms primary resistance. set it up- started it up- ran great!!! checked the "dwell" to see where the pertronix would choose to set it- 50.5 degrees. not bad! drove it around a little bit and it still ran great after setting the timing. tommorow i have a friend who will help me move cars around so i can get it back home. no idea why it had issues still though!

Posted by: Tobra Feb 21 2007, 10:10 PM

It probably still has the issue, but you won't be melting points over it now. Mine ran way, way better with the pertronix thingy. Don't leave the key on, or you might be walking again.

Posted by: Twystd1 Feb 22 2007, 02:47 AM

That kinda confirms the ground issue...

The pertronix has it's own ground wire and doesn't use the dizzy as a ground.

C