7 captured repliesPartial discussion capture · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH1980 911SC not running well or at all when hot
Reported or suspected cause
occurring
Reported cause
No successful repair reported for this finding.
1
Identified cause
1
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0
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Read evidence and context
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Reported cause
your suspecting the CDI unit, have you checked for spark when the problem is occurring.
Leading evidence: 'occurring' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'occurring' (1 discussions; 1 report identifying it and 1 suggest it). The most frequently discussed action is 'Check fuel pump (underneath) will' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
I checked plugs after it wouldn't start and they were fouled and smelled heavily of fuel so at this stage i don't suspect a fuel issue but
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Suggestion · Original poster
I did check spark after it wouldn't start and it seemed weak.
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Performed · outcome unconfirmed · Original poster
I checked spark and it was there but it seemed weak.
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Performed · outcome unconfirmed · Original poster
I changed the coil to a Pertronix Flamethrower and it started - a little hesitantly but then it smoothed out and it ran fine.
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7 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Porsche Forum Australia: 1 discussions
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Hi all
We have a 1980 911SC which started and ran ok recently when cold but eventually when it reached normal operating temperature it starts to miss and run very poorly.
Eventually it stalled and would not start and now it won't start at all - even when cold. Turns over fine but if it is left for a few days it will start. Very wired.
I have changed the plug leads, plugs, distributor cap and coil checks out ok. I suspect the CDI unit but also it may be something fuel related.
Green wire seems fine and doesn't respond to the way it runs at all.
Does anyone in Adelaide have a spare CDI I can borrow to run in our car to confirm that this is or is not the problem?
If it is fuel related, what could it be?
Cheers
David
Edited
7April
by Porsch e
change in circumstances
Not in Adelaide. But have cdi.
you really need to have the car diagnosed by a trusted / knowledgeable mechanic / auto electrician. I had a cdi issue and it drove me mad!
yes it could be cdi starting to fail - I have heard of same problems in a car that was found to have a cracked circuit board in the cdi. It wasn’t an issue when cold, but became an issue when warm / hot. The cracked circuit board started to expand.
have you checked fuel tank and fuel filter? Could be a rusty tank sending particles rearwards.
if you need cdi there are some options that I can recommend from past experience.
new - expensive but good, and all elements of your ignition need to be in excellent health.
https://www.classicretrofit.com/en-au/collections/g-body-911/products/upgrade-cdi-package-sc-turbo
rebuilt original from a highly recommended source in the us.
https://ashlocktech.com/bosch-cdi
justin
your suspecting the CDI unit, have you checked for spark when the problem is occurring. If you have spark when the problem is occurring then that's not your problem
check your Fuel Pump (underneath) will run with 12V directly to pump - & that you can hear excess fuel returning to your tank. So nothing blocked.
If its your CDI is failing; substitute a MSD Streetfire unit ( Part 5520) . I did & IMO it ran better than the original ever did!
Thanks Justin
I had the CDI tested by a Porsche specialist in Adelaide and they said it was fine but I am guessing that was on the nbench and not under hot conditions so it could still be as you said - when its hot it starts to fail.
I recently backdated the heating and after i finished the job it started ok and ran fine until it got hot again and I just got it home as it stalled. It then wouldn't start. I let it cool and tried to start it but no go. I checked a couple of the plugs and they were quite dark and smelled a lot of fuel. I checked spark and it was there but it seemed weak. I changed the coil to a Pertronix Flamethrower and it started - a little hesitantly but then it smoothed out and it ran fine. Haven't tested it for a long run yet but I am going to try soon.
I have contacted Bob Ashlock about reconditioning the CDI so that may be on the cards anyway.
Thanks again for your response.
David
Hi
I checked plugs after it wouldn't start and they were fouled and smelled heavily of fuel so at this stage i don't suspect a fuel issue but
we will see.
Thanks
Hi
I did check spark after it wouldn't start and it seemed weak. Plugs were a little fouled and smelled heavily of fuel. Change the coil to a Pertronix Flamethrower and it started. Haven't run to a really hot temp as yet but we will see if thats the issue when i do.
Cheers
@Porsch e
@Porsch e
I'm pretty sure someone here told me they were reconditioning CDI's.
Will check my messages and see what I can find
Edit: Contact
@PeterW
(in Adelaide) privately and see if he can help with the CDI rebuild
👍
