Dead cylinder help

356 Porsche-related discussions and questions.
Message
Author
User avatar
Jonathan Halpern
356 Fan
Posts: 135
Joined: Sun Jul 18, 2010 10:38 am
Tag: 1964 356C built 7/16/63 1987 911 Carrera
Location: Southern California

Re: Dead cylinder help

#31 Post by Jonathan Halpern »

i simply attached the spark plug from cylinder #3 into wire #3 and allowed it to spark to the chassis/ground to confirm ignition. I had a new spark plug in the engine to keep compression. I also tried the new plug since it was already installed, still a dead cylinder. I pulled the new plug and it was wet with gas.
In further testing, I also realized that cylinder #1 is weak compared to #2 and #4 as tested by pulling spark plug wires from the cap one by one and listening to idle drop.

Jonathan

User avatar
Harlan Halsey
356 Fan
Posts: 2339
Joined: Fri Mar 02, 2012 2:05 pm
Location: No Cal SF Peninsula

Re: Dead cylinder help

#32 Post by Harlan Halsey »

I recall a case recently which puzzled us for quite a while. It turned out that the resistors in the plug ends had begun to fail. Disassembling the plug ends and replacing the resistors with solid conductors was the answer. Probably interferes with radio reception, but the now car runs well.

Jay Darlington
356 Fan
Posts: 1347
Joined: Fri Dec 12, 2008 1:15 pm
Location: coos bay oregon

Re: Dead cylinder help

#33 Post by Jay Darlington »

time for a compression test.
Jay D.
jay darlington

User avatar
Wes Bender
356 Fan
Posts: 4861
Joined: Wed Aug 27, 2008 10:54 am
Location: Somewhere in the Gadsden Purchase, USA

Re: Dead cylinder help

#34 Post by Wes Bender »

.. or a leak-down test. One or the other might show something.
Some days it's just not worth chewing through the restraints.....

User avatar
Jonathan Halpern
356 Fan
Posts: 135
Joined: Sun Jul 18, 2010 10:38 am
Tag: 1964 356C built 7/16/63 1987 911 Carrera
Location: Southern California

Re: Dead cylinder help

#35 Post by Jonathan Halpern »

I can do both, leakdown and compression test. Maybe first is yanking the valve cover and seeing what I can see and checking gaps. All the head work and other work was done by a friend and a very good 356 mechanic. Anything is possible, of course.

Jonathan

WilliamVaughan
356 Fan
Posts: 446
Joined: Fri Dec 03, 2010 7:42 am

Re: Dead cylinder help

#36 Post by WilliamVaughan »

my vote is for "clogged idle jet"

User avatar
Jonathan Halpern
356 Fan
Posts: 135
Joined: Sun Jul 18, 2010 10:38 am
Tag: 1964 356C built 7/16/63 1987 911 Carrera
Location: Southern California

Re: Dead cylinder help

#37 Post by Jonathan Halpern »

Would a clogged idle jet cause a rich condition? I cleaned them and cleaned them again. Easy to try again or swap with another I have on hand.

Jonathan

User avatar
Martin Benade
356 Fan
Posts: 12184
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Re: Dead cylinder help

#38 Post by Martin Benade »

That would not make it rich, and would likely leave that plug bone dry.
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

User avatar
Jonathan Halpern
356 Fan
Posts: 135
Joined: Sun Jul 18, 2010 10:38 am
Tag: 1964 356C built 7/16/63 1987 911 Carrera
Location: Southern California

Re: Dead cylinder help

#39 Post by Jonathan Halpern »

Thats what I assumed. Hopefully will get to the garage later today or tomorrow to continue testing/checking.

Jonathan

User avatar
Paul Hemburrow
356 Fan
Posts: 32
Joined: Sun Feb 09, 2020 4:00 pm
Location: Western Australia
Instagram: @salt_and_pepper_adventures

Re: Dead cylinder help

#40 Post by Paul Hemburrow »

What did you eventually find that resolved the issue?
Paul
Perth, Western Australia

User avatar
Jonathan Halpern
356 Fan
Posts: 135
Joined: Sun Jul 18, 2010 10:38 am
Tag: 1964 356C built 7/16/63 1987 911 Carrera
Location: Southern California

Re: Dead cylinder help

#41 Post by Jonathan Halpern »

Hi Paul,

I’m embarrassed to say I haven’t gotten around to it. Been busy with other cars and projects and the 356 is dormant. I’ll post an update as soon as I get it resolved.

Jonathan

User avatar
Paul Hemburrow
356 Fan
Posts: 32
Joined: Sun Feb 09, 2020 4:00 pm
Location: Western Australia
Instagram: @salt_and_pepper_adventures

Re: Dead cylinder help

#42 Post by Paul Hemburrow »

I had the issue after a carby rebuild but had cylinders 3 and 4. It turned out to be a blocked idle circuit!
Paul
Perth, Western Australia

User avatar
Joris Koning
356 Fan
Posts: 2505
Joined: Thu Mar 27, 2008 12:38 pm
Location: Netherlands

Re: Dead cylinder help

#43 Post by Joris Koning »

Harlan Halsey wrote: Mon Sep 30, 2019 3:12 am I recall a case recently which puzzled us for quite a while. It turned out that the resistors in the plug ends had begun to fail. Disassembling the plug ends and replacing the resistors with solid conductors was the answer. Probably interferes with radio reception, but the now car runs well.
Had this exact thing happen to me yesterday while setting the carbs on my S90. Measured the resistance and it was something like 50M ohm. Luckily I had one original Beru connector in my stash. Runs like a peach now.
'56 Coupe
'57 Coupe
'59 Cab 
'60 Coupe

User avatar
Jonathan Halpern
356 Fan
Posts: 135
Joined: Sun Jul 18, 2010 10:38 am
Tag: 1964 356C built 7/16/63 1987 911 Carrera
Location: Southern California

Re: Dead cylinder help

#44 Post by Jonathan Halpern »

Blocked idle circuit is still my top thought. I’m just concerned with the wet plug on mine.

Jonathan

User avatar
Jon Schmid
356 Fan
Posts: 1797
Joined: Thu Jun 26, 2008 4:32 pm
Location: La Mirada, CA

Re: Dead cylinder help

#45 Post by Jon Schmid »

David Jones' suggestion gets my vote as to your next move. Either eliminate carburetion or ignition as the root cause. I'd be damned if it ended up being a combination of the two.

"Jonathan, you could swap carbs side to side and do not worry about the linkage, just see if it will run at idle and if the problem transfers."

Good luck and enjoy Arrowhead!!

Post Reply