Ignition module failure discovery
#1
Rennlist Member
Thread Starter
Ignition module failure discovery
I just had an engine issue of perhaps interest.
When I built my car I installed switchable ignition coil +12 volt leads like in an old time race car.
When I started the new engine for the first time, it fired right up and after things settled down I decided to test the ignition circuits and viola - one circuit didn't work!
Upshot was my 993 had blown "ignition module" - the current amplifier that handles the coil's current for the ECU.
The engine ran fine on only one circuit and I wonder how many 993 are out there with a blown transistor in their module shutting down one distributor like I experienced.
When I built my car I installed switchable ignition coil +12 volt leads like in an old time race car.
When I started the new engine for the first time, it fired right up and after things settled down I decided to test the ignition circuits and viola - one circuit didn't work!
Upshot was my 993 had blown "ignition module" - the current amplifier that handles the coil's current for the ECU.
The engine ran fine on only one circuit and I wonder how many 993 are out there with a blown transistor in their module shutting down one distributor like I experienced.
#3
RL Community Team
Rennlist Member
Rennlist Member
In my case, I feel, the idle runs incrementally smoother with both plugs firing. At least once a year I unplug the primary distributor to tests the distributor belt and at that time I would become aware of the secondary having a problem. You make a good point though, that I never test specifically for the primary and so testing the primary at the same time in the future would be a good addition to the procedure.
Thank you for your thoughts here.
Andy
Thank you for your thoughts here.
Andy
#4
I just had an engine issue of perhaps interest.
When I built my car I installed switchable ignition coil +12 volt leads like in an old time race car.
When I started the new engine for the first time, it fired right up and after things settled down I decided to test the ignition circuits and viola - one circuit didn't work!
Upshot was my 993 had blown "ignition module" - the current amplifier that handles the coil's current for the ECU.
The engine ran fine on only one circuit and I wonder how many 993 are out there with a blown transistor in their module shutting down one distributor like I experienced.
When I built my car I installed switchable ignition coil +12 volt leads like in an old time race car.
When I started the new engine for the first time, it fired right up and after things settled down I decided to test the ignition circuits and viola - one circuit didn't work!
Upshot was my 993 had blown "ignition module" - the current amplifier that handles the coil's current for the ECU.
The engine ran fine on only one circuit and I wonder how many 993 are out there with a blown transistor in their module shutting down one distributor like I experienced.
#5
Rennlist Member
Thread Starter
In my case, I feel, the idle runs incrementally smoother with both plugs firing. At least once a year I unplug the primary distributor to tests the distributor belt and at that time I would become aware of the secondary having a problem. You make a good point though, that I never test specifically for the primary and so testing the primary at the same time in the future would be a good addition to the procedure.
Thank you for your thoughts here.
Andy
Thank you for your thoughts here.
Andy
#6
RL Community Team
Rennlist Member
Rennlist Member
Andy :-)
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#8
Addict
Rennlist Member
Rennlist Member
Seems you could just unplug the coils one at a time. If the car dies, you have a problem? That's how we first found my (first) ignition module problem.
#9
Drifting
a pea sized blob of heat sink compound wouldn't hurt either
#11
Just had this on my 993. I did the usual routine belt failure check by pulling each coil and seeing if it starts. It was only firing on the driven/secondary distributor. Swapped the wires on each coil positive and negative and the issue moved to the secondary coil and the primary was working which prove the coils were ok. It seems that only one channel on the ignition module was working. Took a punt and ordered a new module and now have two working distributors. I also found that just putting a timing light on each coil lead and checking for operation of each distributor is a better was of checking operation also. Really happy it wasn’t a wiring issue or ECU.
Thanks for the above information as it helped my diagnosis immensely.
Cheers
Todd
Thanks for the above information as it helped my diagnosis immensely.
Cheers
Todd
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Brando 993 (09-18-2023)
#12
Pro
Long time ago I purchased a tool called OK SPARK. It's a little pricey but it will reveal all of your ignition issues without wrenching on anything.
I discovered a failing spark plug boot which otherwise would have never found.
I discovered a failing spark plug boot which otherwise would have never found.
#13
Just had an issue with mine.
The PO has relocated it from under the seat to an aluminum block to mount seat down lower I believe.
So, I remove it from the aluminum block and just had it hanging in front of the seat.
Not thinking about the module, Took the car for a shake down drive nearby and it was running fine and then all of of sudden just dies.
Cranks but won't start. Smells like fuel. Tried DME, no luck. Then think maybe the module needs to be grounded. Try holding it to metal, no luck. Then I see it's split open. Unbelievablly, the PO not only had a spare DME, but also a spare module in the trunk. Swap it out and it fires right up.
Now, my questions is, when I look it up on the parts sites, there is also an insulator? Is that needed? I've got it mounted back where it should be but want to make sure I'm good.
The PO has relocated it from under the seat to an aluminum block to mount seat down lower I believe.
So, I remove it from the aluminum block and just had it hanging in front of the seat.
Not thinking about the module, Took the car for a shake down drive nearby and it was running fine and then all of of sudden just dies.
Cranks but won't start. Smells like fuel. Tried DME, no luck. Then think maybe the module needs to be grounded. Try holding it to metal, no luck. Then I see it's split open. Unbelievablly, the PO not only had a spare DME, but also a spare module in the trunk. Swap it out and it fires right up.
Now, my questions is, when I look it up on the parts sites, there is also an insulator? Is that needed? I've got it mounted back where it should be but want to make sure I'm good.
Last edited by motobri; 05-27-2021 at 09:34 PM.