Symptoms of a Failing CDI

[slow&rusty]

Hey Guys - Took my '89 for a nice drive yesterday.

About 30-minutes into the drive the car stumbled and died and refused to start. I let it sit for a few minutes and it fired up right away. I decided to let it sit for an hour and proceeded home.

On the way back every 10-minutes it would instantly shut off. If I let it sit for 5-ish minutes it would fire up without any issue and I was able to drive for another 10-minutes until it died again.

Do you guys think this might be the CDI on its last legs? It's the original unit from '89.

Thanks,
Yasin

[Tonger]

Definitely could be the CDI. It starts to show symptoms of failure as the car gets warmer. The fact that you can restart and drive suggests against a fuel issue.

Bob Ashlock is terrific at rebuilding these CDI units for a very reasonable cost - fast turnaround too.

https://ashlocktech.com/bosch-cdi

[908/930]

I would start checking electrical connections, could be a weak connection getting hot and expanding. Need to verify that there is no spark.

[slow&rusty]

@Tonger - Thanks! I was looking at the Classic Retrofit units, but I'll call Bob Ashlock, I had not heard of him before or his CDI rebuilding services.

Much appreciated,
Yasin

[flightlead404]

I have a good working when removed CDI from an '86 I'll sell, if it's the same part.

[abrokenframe]

Originally Posted by slow&rusty

Hey Guys - Took my '89 for a nice drive yesterday.

About 30-minutes into the drive the car stumbled and died and refused to start. I let it sit for a few minutes and it fired up right away. I decided to let it sit for an hour and proceeded home.

On the way back every 10-minutes it would instantly shut off. If I let it sit for 5-ish minutes it would fire up without any issue and I was able to drive for another 10-minutes until it died again.

Do you guys think this might be the CDI on its last legs? It's the original unit from '89.

Thanks,
Yasin

My car had the same symptoms when my CDI was failing. Would drive great for about half an hour, then would start backfiring and die. It'd fire up again after sitting for an hour or two.

[mark houghton]

Most likely CDI, considering your symptoms. I guess you could further diagnose by placing a bag of ice on top of the cdi and see if that greatly extends the time between driving and shutdown....assuming it's heat soak related. Just a thought.
Another possibility might be relay under the drivers seat...overspeed relay I think its called. Years ago mine gave me fits with sudden shutdowns and the short term remedy was to reach under the seat and rattle things around. Eventually removed it and re-soldered all circuit board traces and spread the prongs on the plug. Did the trick.

[slow&rusty]

Thanks guys. I'll will try the ice and also look at that overspeed relay (I did not even know about that one!).

Much appreciated.

[krasuskyp]

Sir Yasin - bummage, dewd. Destiny for all, unfortunately with these 8 )

Likely CDI, but also as likely to be confounded yellow relay... or... gdamn fuel pump fuse & wire if you've not yet relayed your FP's individually (as you should have by heh heh!).

HTH, report back!

Good news is... least you have A DOZEN other f'n wundercarz to bomb around in until sorted!!! Mah MAN...

[slow&rusty]

Originally Posted by krasuskyp

Sir Yasin - bummage, dewd. Destiny for all, unfortunately with these 8 )

Likely CDI, but also as likely to be confounded yellow relay... or... gdamn fuel pump fuse & wire if you've not yet relayed your FP's individually (as you should have by heh heh!).

HTH, report back!

Good news is... least you have A DOZEN other f'n wundercarz to bomb around in until sorted!!! Mah MAN...

Thanks buddy! Agreed..I was probably on borrowed time. Thanks for the heads-up on the yellow relay as well. One thing I have not done is individually relayed the fuel pumps...enlighten me puh-leeeze sir!

I will report back for sure.

On the cars...there are a back-up for the back up.

Chat soon!
Yasin

[David]

Any news on the problem?

Here's the M&W Pro10 CDI I was talking about if you're looking to replace with something besides Permatune. I wasn't able to find anyone making a plug and play harness though.

https://outfrontmotorsports.com/products/m-w-pro-10-cdi-ignition-box

[krasuskyp]

here ya go brohammage!:

https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/575052-930-fuel-pump-fuse-overload-solution.html

on mine the red wire going into the fuse block was visibly cooked - give it a quick looksee

if yours is (somehow lol, guaranteed failure) good, put it on your to do list

I'd skip running the wires through the metal cover, that wasn't the best idea - but otherwise it's a quick and easy and IMPORTANT fix!!

hope you find it soon dewdstick!

[slow&rusty]

Originally Posted by David

Any news on the problem?

Here's the M&W Pro10 CDI I was talking about if you're looking to replace with something besides Permatune. I wasn't able to find anyone making a plug and play harness though.

https://outfrontmotorsports.com/products/m-w-pro-10-cdi-ignition-box

Originally Posted by krasuskyp

here ya go brohammage!:

https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/575052-930-fuel-pump-fuse-overload-solution.html

on mine the red wire going into the fuse block was visibly cooked - give it a quick looksee

if yours is (somehow lol, guaranteed failure) good, put it on your to do list

I'd skip running the wires through the metal cover, that wasn't the best idea - but otherwise it's a quick and easy and IMPORTANT fix!!

hope you find it soon dewdstick!

Thanks broham Paulie! I appreciate the thread forward and will read-up. Awesome.

David - I ended buying a rebuilt unit from Bob Ashlock (many thanks to Tonger for the great suggestion). I called Bob, super nice guy and he had one of his rebuilt units shipped out and in my hands in a few days. The M&W would have been cool, but I did not want to butcher my wiring harness.

I installed Bob's rebuilt CDI (easy once you remove the intercooler) and the car started immediately. I have to still road test it but currently doing some other catch-up maintenance this weekend and then will have the car back on its feet by next week.

Thanks all!
Yasin

[Dcexige]

Going through something similar and great referral! Much appreciated

[slow&rusty]

Some pictures to share!

[gsxrken]

That’s interesting- I had Bob redo mine maybe 10 years ago. Great after sale support. But mine doesn’t have that LED indicator your instructions mention, and it does still have the high pitched whistle.

[slow&rusty]

Ken - Bob must have reworked the CDI over the years to incl, the LED which is always "on" when the car is running and no longer has the high-pitched whine.

Regards,
Yasin