yep another no start problem, been readn alot of um. this is due to the fact that the road slipped out from under my back tires and swung a road sign in front of my F/L fender denting it ever so gently. Now it wont start, i get no spark. All relay fuses, coil, speed sensor, dme relay, grounds, alot of stuff looks & test ok. hopefully someone has an idea im overlooking. its got me in a twist so im giving it a break right now before i do something bad. But i still think Porsche is answer to what ever the question was

 

ell, welcome, but I don't have any ideas for you. Clearly the accident jarred osmething loose in the electricals, but what I don't know.

 

I take it this is along the lines of a 924/944 since you didn't specify. Is the tach bouncing when you crank the engine over? It should move ever so slightly? If not, it is a reference sensor problem or connection there. Could also be a DME issue. You could try giving the DME a pop with a rubber mallet and see if that jars anything. If it does start then, you have a cold solder joint on the board.

 

ya the tach does move, but ill have to try that mallot idea if nothing else it might make me feel better.

 

oh it is an 87' 944S, sorry

 

Just thought of something. How can you tell if the ECU is getting pwr from the ignition switch? My radio isnt getting pwr either and the fuses a good. I'm at the point of suspecting the switch. It looks like too much fun removing it.

 

You can check the ECU with a voltmeter -- sounds like you'll need one on this detective mission. It's best to get a higher impedance (quality one) too when fussing around with digital electronics, too. With that and a wiring diagram and a lot of time and patience you will find the problem, eventually.


There is one thing it might be, if your car has these things in it.

Maybe Porschedoc knows: Do Porsches has any circuit breakers rather than fuses?

What they are? My vette and some other GM high-end cars have three master relays -- VERY FAST acting, "fuse saving" breakers, that open instantly (or at least faster than a fuse can blow) in some circumstances, each upstream of a number of fuses: one "oversees" all the fuses for the instruments and radio and etc., another all the body control (shock computers, ABS, etc), and third -- I'm not sure. they are identified as a box rather than a fuse symbol in the wiring diagram and labeled something like "Master Relay" or Master Prot."
In some circumstances where the short circuit might be a transient or when it occurs immediately on start up, these relays open, killing all power to a whole portion of the car (and meaning that the fuse to the offending circuit or device does NOT blow). They are supposed to close again if the ignition is turned off. But sometimes they fail and stay open permanently. Then you have an electrical outage of a whole portion of the car and yet no matter how hard you look there is no blown fuse -- very frsutrating.

Its not uncommon for a newer model 'vette that has been hit, particularly in the passenger's side door area (close to the body electrics fuse box) to have one or more of these breakers shook up so bad they won't operate-- all the fuses are still good but you have a whole section of electrics that doesn't work.

 

If you have no spark at the coil, i would start there. Do you have power to the coil? I have heard the ignition switch doing something similar, though i don't have any personal experience with one going out. If the radio worked before, and not now, then you may be on to something, as it is completely isolated from the DME. I am having similar problems that started with my car last week. Currently have the DME and KLR out to fix some cold solder joints on the board that i think are the culprit.

Porsches do not use the circuit breaker system, though it would be nice if they did. Still just fuses and relays.

 

well, the rubber mallot didnt make me or the car feel any better. I do have 12+V at the coil and ohms out ok. But what I dont get is if im getting pwr to it why wont it spark, even directly off of the coil itself? Or should i ask, how many phases does the coil go through before it produces a spark? And whats a KLR? The odds of all the plugs going bad are probably slim but im on my way now to get a spark tester, and extra coil wire, as i have been using the plugs out of the car for testing purposes.

 

If you have power to the coil and no spark, i am guessing the coil is probably bad or the DME is bad. I would start with the coil since it is about 50 bucks. Or maybe a bad coil wire? A klr is part of the boost regulation etc on the turbo cars, your NA will not have it.