Upgrading Ignition
12-17-2009, 03:47 PM
#1
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Upgrading Ignition
I have installed a pertronix ignitor ignition kit on my 74 911 2.7. It will not start and did backfire once. I've ordered a new coil since my old one only registers .5 ohms resistance and the Ignitor says it requires a minimum of 1.5 ohms.
Has anyone had this problem or have advice. I replaced my Bosch CD unit some years ago with a Perma-tune. Other than that, the ignition setup is stock.
Has anyone had this problem or have advice. I replaced my Bosch CD unit some years ago with a Perma-tune. Other than that, the ignition setup is stock.
12-17-2009, 04:07 PM
#2
RL Technical Advisor
David,
Precisely,......tell me everything about your installation.
Did you have the key on for several minutes during this time?
No spark at this moment?
Precisely,......tell me everything about your installation.
Did you have the key on for several minutes during this time?
No spark at this moment?
12-17-2009, 08:51 PM
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When I first installed the Pertronix, I followed the instructions sent with it which were wrong for the CD ignition. I went online and got the correct wiring schematic and wired it again. I still did not get a spark which made me wonder if I'd ruined the ignitor. I tested the coil for resistance and it tested at .5 ohms resistance so I ordered a Pertronix Flame Thrower coil but have not gotten it yet. I never left the key on long enough to do any damage; just enough to get the fuel pressure up. My 2.7 engine has been rebuilt to RS specs with S cams, JE HP forged pistons and the heads were done by Peter Dawes. The engine bench dino was 235hp. Cole Scrogham of Synergy Racing did the rebuild. I have had problems with the points for some time and decided on the Pertronix system. I hope I haven't made the wrong choice. Any help will be much appreciated. David
12-18-2009, 12:57 AM
#4
RL Technical Advisor
I'm a big fan of Pertronix ignitors and have installed a lot of them over the years without issues.
One thing,...they are not forgiving of wiring errors and you may have toasted it if connected wrong. Measure the resistance across the red & black leads for me.
One thing,...they are not forgiving of wiring errors and you may have toasted it if connected wrong. Measure the resistance across the red & black leads for me.
12-18-2009, 12:14 PM
#6
"I've ordered a new coil since my old one only registers .5 ohms resistance"
Which means that the ignitor was subjected to about 24 amps of peak current
and most likely damaged the unit. The correct coil is critical for an ignitor type
of ignition versus a CD type which the Bosch OEM was.
By the way, an ignition "upgrade" over the Bosch unit has no merit/value in reality,
as there are no data to support that "upgrade". But it's always a good sales gimmick
to get people to buy mods.
Which means that the ignitor was subjected to about 24 amps of peak current
and most likely damaged the unit. The correct coil is critical for an ignitor type
of ignition versus a CD type which the Bosch OEM was.
By the way, an ignition "upgrade" over the Bosch unit has no merit/value in reality,
as there are no data to support that "upgrade". But it's always a good sales gimmick
to get people to buy mods.
12-18-2009, 12:18 PM
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Okay; I agree that "upgrade" was not the correct term. My Bosch CD unit went bad about 10 years ago and I replaced it with the Perma-tune unit. Thank you for your comments. I have tested the Pertronix unit and I think it is fried. I appreciate all input.
David
David
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12-18-2009, 10:50 PM
#8
RL Technical Advisor
The Bosch CD box is a very durable and repairable system. I'd recommend having it fixed and reinstalling it with its matching coil followed by a new Ignitor.
12-19-2009, 01:16 AM
#10
"I have ordered the Pertronix flame thrower coil. Will that work okay with my CD unit?"
Most any conventional ignition coil will work with a CD unit.
As long as the turns-ratio is about 100 - 120 or less, the
Pertronix coil will be fine.
Most any conventional ignition coil will work with a CD unit.
As long as the turns-ratio is about 100 - 120 or less, the
Pertronix coil will be fine.
