#4 cylinder not combusting

356 Porsche-related discussions and questions.
Message
Author
User avatar
Adam Willis
356 Fan
Posts: 31
Joined: Tue May 06, 2008 10:59 pm
Location: Charleston, SC

#4 cylinder not combusting

#1 Post by Adam Willis »

To the 356 community writ large,

While i am not knew to the Reg, this is my first post. I have a dilemma which I am having difficulty narrowing down...

Background info...
-1958 356A coupe
-Normal 1600 (stock as far as I know)
-I have started the engine once since 1995 (yep, I know...long time, lots of issues)

Issue...#4 cylinder shows no sign of combustion on the spark plug...(I chose the word combustion because I am not sure why it is not combusting). All other cylinder (spark plugs) look good and slightly rich.
-Steps taken to solve issue
--Checked points, gapped to .016" inch
--Check timing (#1 TDC, measure 6.5mm to right of OT mark and set static timing at that mark...~5*BTDC).
--adjusted valve to initially .004 and .006 respectively, however, I then set them at .006 and .008 respectively just to give myself a warm fuzzy that the valve were seating (hasn't run in so long, want to get maximum seating pressure)
--checked #4 spark plug wire...firing with spark plug out and engine cranked
--replaced all spark plug...just to ensure it was not a failed spark plug...same issue with the NGK's
--checked compression on #4...120 after three rotations...It did bleed down slowly, but I am not sure if that was the gauge, the o-ring on the gauge or another issue which I will investigate shortly.
--Rebuilt Zenith carburetors...interestingly enough, the drive side card was not getting a fuel shot from the accelerator pump...removed and again rebuilt and did bench test...found a plugged pump set at the bottom of the accelerator well...accelerator pump working now...adjusted pump rod according to the manual. Did not do a volume test, just adjusted the rod length. however, both carb have same pump shot and are working. Additionally, the driver side carb idle air mixture screw on #4 cylinder does not do anything to the idle quality or the RPM's...this is one area were i need of that Reg expertise, the other area is the distributor.

Soooo, long story getting shorter,

Question, can a Zenith 32 provide fuel in only one venturis? I did check the main jet and the idle jet...both appear to be clean. Is it possible that I am only getting fuel from the same bowl into one of the venturis? I know they are both separate throats, but it is interesting that the engine runs, and rather well...without a load. With a load, forget it...definitely feels like a cylinder is down.

The other question has to do with the distributor...yep, you guessed it...I am running a 009. It was with the car when I purchased it a very long time ago and have not bothered to buy a correct one yet because I wanted to get it running correctly first (I use the term correctly in a lose fashion). I have ordered a BR18...just not here yet. The question is since it is a 009, is it indexed differently than the original or different from how the manual states to install the distributor? I have heard that the 009 is not set the same as the BR18, although the firing order is the same...currently, the 009 int set with the #1 post on the cap at roughly the 5 o'clock position. Would this be correct for this type of distributor...and does it even matter. I am looking at a red herring on this one??

I am sure I have forgot some info which would make it easy to diagnose, but thanks in advance for any thought on this problem...

Adam

User avatar
Ron LaDow
356 Fan
Posts: 8092
Joined: Wed Mar 26, 2008 11:45 am
Location: San Francisco

Re: #4 cylinder not combusting

#2 Post by Ron LaDow »

Welcome to the list. It's a two-drink minimum, but the show's worthwhile.
Swap the carbs left-to-right. The linkage won't fit, but you don't care since you're just looking for fire in the hole. If the problem follows the carb, you have your villain. If not, go back to the ignition and look closer.
There is no magic; given compression, fuel and a (reasonably timed) spark, it will fire.
Ron LaDow
www.precisionmatters.biz

User avatar
Adam Willis
356 Fan
Posts: 31
Joined: Tue May 06, 2008 10:59 pm
Location: Charleston, SC

Re: #4 cylinder not combusting

#3 Post by Adam Willis »

Ron,

Thanks for the reply...great idea and an easy one...running out of ideas...however, I think it might be a two bottle minimum.

Adam

User avatar
David Jones
Classifieds Moderator
Posts: 7323
Joined: Tue Mar 25, 2008 6:32 pm
Tag: I wish I knew as much as I think I know.
Location: Kentucky

Re: #4 cylinder not combusting

#4 Post by David Jones »

You may have a manifold leak which will give the same symptoms. If the carb swap side to side leaves the problem on the same cylinder that is a likely answer. As far as the 009 goes it will have an index mark just like on the 018 if it was made in Germany and will sit in the same place as the 018. You can advance the timing once the engine is running to give it a max of 30 degrees at 3000 rpm and it will perform reasonably well. It may then want to idle high because of the higher advance at static.
By the way Adam, where are you? It is always useful to give at least an idea of your location as there may be a registry member in the vicinity who can assist you. Right now I guess you could live in the same town as I do.
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
David Jones #9715

User avatar
Adam Willis
356 Fan
Posts: 31
Joined: Tue May 06, 2008 10:59 pm
Location: Charleston, SC

Re: #4 cylinder not combusting

#5 Post by Adam Willis »

Dave,

Thanks...while the engine was running, I did spray some WD40 around the bottom of the intake manifold...looking for any change in engine...nothing, although WD40 is not the best tool for that diagnosis
...forgot that one about location, thanks. I live in Dayon, Ohio...will add my address to my profile.

Adam

User avatar
Ron LaDow
356 Fan
Posts: 8092
Joined: Wed Mar 26, 2008 11:45 am
Location: San Francisco

Re: #4 cylinder not combusting

#6 Post by Ron LaDow »

Adam,
You're welcome.
David is always a good source for info, so follow his advice with confidence.
But I'd like to add a caution to trouble-shooting in general: When you test for a spark at a cylinder, leave the plug in there and try a new/known plug lying on the engine case. If you get spark, swap to that plug.
If you pull the plug, the rotation will blow combustible mixture all over, including near that plug you're testing.
Ron LaDow
www.precisionmatters.biz

User avatar
David Jones
Classifieds Moderator
Posts: 7323
Joined: Tue Mar 25, 2008 6:32 pm
Tag: I wish I knew as much as I think I know.
Location: Kentucky

Re: #4 cylinder not combusting

#7 Post by David Jones »

Adam, you have many 356 owners in the area. Dick Weiss is one of the more knowledgeable folks in the local club and you have Mark Schlachter in Cincinnati. Here is a link to the local 356 club if you do not already know of them. I used to be a member myself until I moved to Kentucky from Lima Ohio.
http://dreistaatengruppe.com
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
David Jones #9715

User avatar
Peter Boettcher
356 Fan
Posts: 269
Joined: Wed Mar 26, 2008 6:37 pm
Location: Cincinnati, OH

Re: #4 cylinder not combusting

#8 Post by Peter Boettcher »

Hi David,

The Drei Staaten Gruppe certainly misses having you as a member, but it is great to see you posting again and doing better.
Adam, we have lots of resources in our area, you can contact me via our website.
In Dayton you also have Yuri at The Garaj who is a real 356 expert. The number is: 937-294-2400.
Dick Weiss can also solve many problems over the phone. He is our local 356 Encyclopedia Britannica.

Get in touch with us, and we would welcome a new member too.

Peter Opa Boettcher
Cincinnati, OH
Peter Boettcher

User avatar
Doug McDonnell
356 Fan
Posts: 6061
Joined: Sat Apr 05, 2008 8:21 am
Location: Augusta,Michigan

Re: #4 cylinder not combusting

#9 Post by Doug McDonnell »

Peter Boettcher wrote:Hi David,

The Drei Staaten Gruppe certainly misses having you as a member, but it is great to see you posting again and doing better.
Adam, we have lots of resources in our area, you can contact me via our website.
In Dayton you also have Yuri at The Garaj who is a real 356 expert. The number is: 937-294-2400.
Dick Weiss can also solve many problems over the phone. He is our local 356 Encyclopedia Britannica.

Get in touch with us, and we would welcome a new member too.

Peter Opa Boettcher
Cincinnati, OH
I love your description of Dick Weiss "He is our local 356 encyclopedia Brittannica."
1965 356C 2000 BMW 740i Sport 1967 Honda CL77 There is never enough time to do it right, but always enough time to do it over.

User avatar
Adam Willis
356 Fan
Posts: 31
Joined: Tue May 06, 2008 10:59 pm
Location: Charleston, SC

Re: #4 cylinder not combusting

#10 Post by Adam Willis »

Dave, Pete,

Thanks for the resources...I will certainly check out the website and club...been here a year now, so don't know the local area experts yet. About to pull the carbs and get a borescope into the manifold...see what I can see, then swap and the carbs...should give me a direction to go.

Adam

User avatar
Richard Shilling
356 Fan
Posts: 790
Joined: Sun Apr 20, 2008 12:40 pm
Tag: Ex 356 Mechanic
Location: Shoreline, Washington, USA
Contact:

Re: #4 cylinder not combusting

#11 Post by Richard Shilling »

Swapping carbs is a good idea, but quicker and easier is to swap spark plug connectors and see if the dead cylinder follows the connector.
Richard Shilling
1965 356C dolphingrey 

User avatar
Adam Willis
356 Fan
Posts: 31
Joined: Tue May 06, 2008 10:59 pm
Location: Charleston, SC

Re: #4 cylinder not combusting

#12 Post by Adam Willis »

Pulled Driver Carb, tin and manifold...scoped both ports while turn engine over (by hand). Valve train looks good, nothing broken, stuck or otherwise out of the ordinary. Manifold to head gasket looked uniform and no spots pointing toward a leak. Sooooooo, I tore into the carb again...it is interesting what you find the more you do it (although the objective is to do it right the first time-just doesn't seem to work with me, hmm). Lets see, the butter fly screws were lose, real lose...tighten and peened them and two of the bolt hole securing the throttle base to the body are stripped (the long one that go thru the body). While these are certainly adding to a vacuum issue within the #4 throat, I would think it still should have had enough vacuum to pull fuel from the bowl thru the emulsion tube into the chamber...

Looks like I am going to have to helicoil the two body screw holes...anyone know where to get those helicoil of the top of mind? Going to order new manifold gaskets, fix carb body holes and try it again.

User avatar
David Jones
Classifieds Moderator
Posts: 7323
Joined: Tue Mar 25, 2008 6:32 pm
Tag: I wish I knew as much as I think I know.
Location: Kentucky

Re: #4 cylinder not combusting

#13 Post by David Jones »

They are 6mm threads. Standard thread pitch of 1mm. Any good hardware store or local auto parts store.
If you lived closer to me you could have brought them over this evening and we could have fixed them.
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
David Jones #9715

User avatar
Adam Willis
356 Fan
Posts: 31
Joined: Tue May 06, 2008 10:59 pm
Location: Charleston, SC

Re: #4 cylinder not combusting

#14 Post by Adam Willis »

Dave,

I knew I liked Kentucky, just didn't know why...thanks numbers...this will make it easier. Out to town this weekend, but back to it on Monday. Once fixed, I am going to swap with the passenger side and hope all is well...if not, I got issues Lucy...

Richard,

Thanks...I did pull the plug and ground it to check for spark...there was spark...its weird, the cylinder shows no sign of combustion...the plug is absolutely spotless, there is no fuel oder, there is no oil on the plug, thee is no sign of anything...no misfire, no backfire, nada! Yet I get good compression, valve train is working, at the correct time...distributor is correctly indexed and timed...just no combustion in the "combustion process" which happens in a cylinder. i am stuck on the fuel being the culprit...however, I am going to check everything, again...as soon as I get it back together.

User avatar
Peter Boettcher
356 Fan
Posts: 269
Joined: Wed Mar 26, 2008 6:37 pm
Location: Cincinnati, OH

Re: #4 cylinder not combusting

#15 Post by Peter Boettcher »

Adam,
Reading your findings on the condition of the throttle plates and stripped screws makes me very nervous about what that carb has been through at the hands of a Turkey Mechanic.
Zenith carbs are plentiful and relatively inexpensive on Evilbay and the Samba.
Dick Weiss and I have lots of Zenith bodies and throttle plate assemblies, should you decide to go that route.
Also be sure that the top cover is completely flat and not warped. I smooth them down with 1,000 grit paper on a piece of glass, as well as the carb body.
Blocks Books carries Charlie Whites excellent book on rebuilding Zenith carbs and it is full of tips as well.

Keep us advised, good luck and welcome to the neighborhood.

Peter Opa Boettcher
Cincinnati, OH
Peter Boettcher

Post Reply