Porsche 914 2.0L not getting any fire from coil/ignition

VW based Porsche. In a league of its own.

Moderator: Piledriver

Post Reply
91422.7
Posts: 3
Joined: Thu Apr 09, 2015 12:28 am

Porsche 914 2.0L not getting any fire from coil/ignition

Post by 91422.7 » Thu Apr 09, 2015 12:39 am

I have a 1970 Porsche 914 which I have installed a 1975 Porsche 914 2.0L engine in and added dual Weber 40 IDF carbs. Distributor has been upgraded to electronic ignition (Petronix). I have routed the two appropriate wires from the engine compartment relay board, (1) blk/red hot wire to #15 + on Coil and (2) blk/purple wire from tach to Coil - post. Then I ran the red wire from the Distributor to the + on the Coil and black wire from coil to the - on coil. With test light it shows all four post on the coil (- and +) are hot! When I crank the engine I'm not getting any fire from the coil wire or the plug wires when checked! I don't know the history of the Petronix Ignition! Suggestions..Thank you

User avatar
Piledriver
Moderator
Posts: 21747
Joined: Sat Feb 16, 2002 3:01 am
Location: Van Alstyne, Texas

Re: Porsche 914 2.0L not getting any fire from coil/ignition

Post by Piledriver » Thu Apr 09, 2015 2:38 am

Welcome to the STF!

You should be able to test your coil by grounding the negative side briefly with a jumper wire.
It will spark when you break the ground connection as the magnetic field collapses.

The good news is you should be able to simply install a set of points and condenser to get going/as a troubleshooting aid at least, as long as you have a std coil.

Unfortunately (AFAIK) the aftermarket modules have ~zero reverse polarity protection, touch the leads backwards and they die an ~instant death, they have also been known to just die for no apparent reason, or worse, just go flake, esp when hot.

I have run both compufire and a pertronix at times, but I never personally "tested" them to see if it would let the magic blue smoke out when hooked up backwards.
I did have to replace the pertronix due to getting flaky on hot days. I have also replaced a few for other people.

(I replaced my flake pertronix with compufire, then with a vanagon hall effect setup, then used that to trigger a high power Jacobs ignition setup, then Megasquirt with sequential GM LS2 coils, but I digress...)

I do prefer the Compufire widely spaced magnet wheel setup vs the tiny pertronix trigger ring, but they both work well when they work.

The primary of the coil will show power on both terminals if the "points" aren't closed, as there is no voltage drop in an open circuit.

The stock coil primary has a ~3ish-4 ohm resistance, and with no pull down (from the points or substitute) full voltage will be visible on both terminals.

If your coil has less resistance you likely need a ballast resistor, which is neither good//bad, the stock coils simply had it effectively built in. If you have an ammeter the coil should pass ~3-4A from 12v if stock spec.

I usually suggest drawing ignition power ~direct from the alternator to a relay ~on the coil mount or close by, and use the switched power from the key to control the relay---skips the loss in the ignition switch and about 20 feet of 40 year old wire.
(the ignition will work best running on full power, I have seen as little as 8v to the coil in a running setup through the ancient stock wiring)

Do the same for the headlights, its a huge and almost free lighting upgrade, and really ~mandatory if you upgrade the headlights to more powerful units. The Porsche headlight swicthes are expensive, and are known weak items. (75/76 models have a relay for the headlights BTW, so even Porsche/VW knew it was a problem.)
I, for one, regularly embrace our new robot overlords, as I am the guy fixing the robots...

91422.7
Posts: 3
Joined: Thu Apr 09, 2015 12:28 am

Re: Porsche 914 2.0L not getting any fire from coil/ignition

Post by 91422.7 » Thu Apr 09, 2015 8:59 am

Thank you for your suggestions, I will start checking out everything you mentioned and get back with you! Have a great day! Roy :D

91422.7
Posts: 3
Joined: Thu Apr 09, 2015 12:28 am

Re: Porsche 914 2.0L not getting any fire from coil/ignition

Post by 91422.7 » Thu Apr 09, 2015 10:19 am

..Ok, I tested the coil by grounding the neg side and got a spark! I had just recently purchased the coil which was suppose to be a OEM replacement from Auto Zone. The primary on the coil shows power on both/all terminals - & + which is normal! I checked my Ohms resistance on the coil, showed 3-4A stock specs. Still no spark/power coming out of the center coil wire that leads to distributor. I don't think I've fried my Petronix but not sure how to test it! I personally have never seen it work, it came with the engine and distributor when purchased! I've attached some pics of the relay board and coil and distributor. What do you suggest at this point? Thanks .....I haven't ran a wire from the alternator to a relay on the coil yet for better ignition, but will later! At this time the engine is turning over good from the ignition!
You do not have the required permissions to view the files attached to this post.

Post Reply