Notices
928 Forum
Sponsored by:
Sponsored by: 928 Specialists

Badly Scored Distributor Cap - Help 1989 S4

 
Old 11-06-2011, 05:59 PM
  #1  
NC928S4
User
Thread Starter
 
NC928S4's Avatar
 
Join Date: Jan 2011
Location: Cary, NC
Posts: 655
Likes: 0
Received 0 Likes on 0 Posts
Default Badly Scored Distributor Cap - Help 1989 S4

I recently changed out all ignition parts but when I started her back up there was a significant knock/scraping noise from the right distributor cap. By the time I turned the engine off(10 seconds) the noise was pretty much gone. Tune up worked great, lots more power. Case closed.

Last week I decided to look at what had caused the noise and found a badly scored distributor contacts on 3 of the 4 posts with the middle the worst. Along with brass shavings. I double checked fitment and all looked fine. I figured I had a poorly manufactured Distributor cap. Got a new cap and rotor and got the same problem.

There does not appear to be a way to put things back together off-center but from the wear pattern that sure looks like something is off center by 1/32" to 1/16ö.

The timing belt was done 5 months ago and I never heard the knock or bothered to check the old distributor before I replaced it.

Any ideas?
Attached Images  
NC928S4 is offline  
Old 11-06-2011, 07:00 PM
  #2  
Lizard928
Super User
 
Lizard928's Avatar
 
Join Date: Apr 2003
Location: Abbotsford B.C.
Posts: 9,509
Likes: 0
Received 0 Likes on 0 Posts
Default

It is possible that you are missing a locating pin/bolt for that cover.
Lizard928 is offline  
Old 11-06-2011, 07:02 PM
  #3  
ammonman
Addict
Rennlist Member
 
ammonman's Avatar
 
Join Date: Jul 2008
Location: NW Arkansas
Posts: 2,033
Likes: 0
Received 1 Like on 1 Post
Default

Cam cover not correctly installed/seated? Backing plate for cam cover is loose? Broken cam shaft nose? What brand are the rotor and cap? Only so many possibilities to get the two mis-aligned.

Mike
ammonman is offline  
Old 11-06-2011, 07:13 PM
  #4  
Landseer
Addict
Rennlist Member
 
Landseer's Avatar
 
Join Date: Sep 2007
Location: Frederick, Maryland
Posts: 11,320
Received 5 Likes on 3 Posts
Default

I've caused that on the driver's side by not seating the inspection cover properly.
Landseer is offline  
Old 11-06-2011, 07:57 PM
  #5  
Mrmerlin
Petie3rd
Rennlist Member

This Post Sponsored by:
Dow Corning« & DeoxIT«
 
Mrmerlin's Avatar
 
Join Date: May 2004
Location: Philly PA
Posts: 22,749
Received 3 Likes on 2 Posts
Default

take the cover off and make sure the the 2 hollow roll pins are sticking out from either the rear cover or the front cover so the front cover will be aligned when fitted .

These are spring steel roll pins that have the bolts passing through them,
its possible for one or both to get pressed into either part of the either cover and then get pressed flat so they dont hold the cover perfectly straight,
based on your findings i would say it probably the top roll pin thats not in the correct position
Mrmerlin is offline  
Old 11-06-2011, 09:18 PM
  #6  
NC928S4
User
Thread Starter
 
NC928S4's Avatar
 
Join Date: Jan 2011
Location: Cary, NC
Posts: 655
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks, lots of things to inspect on the tear down tomorrow. It's reassuring that there are possibilities beyond me hosing things up.

It is possible that you are missing a locating pin/bolt for that cover.

NC928S4-> There are no pins that I see. The Rotor can only fit one way. The Cap has to fit so wires connect. So I don't think I screwed that up.

Cam cover not correctly installed/seated? Backing plate for cam cover is loose? Broken cam shaft nose? What brand are the rotor and cap? Only so many possibilities to get the two mis-aligned.

NC928S4-> Will check. All stuff was Bosch from 928sRUs who also gave me replacement parts no questions asked.

I've caused that on the driver's side by not seating the inspection cover properly.

NC928S4-> More to check thanks.

take the cover off and make sure the the 2 hollow roll pins are sticking out from either the rear cover or the front cover so the front cover will be aligned when fitted .

These are spring steel roll pins that have the bolts passing through them,
its possible for one or both to get pressed into either part of the either cover and then get pressed flat so they dont hold the cover perfectly straight,
based on your findings i would say it probably the top roll pin thats not in the correct position.

NC928S4-> Thanks Merlin. Will check.
NC928S4 is offline  
Old 11-06-2011, 11:05 PM
  #7  
the flyin' scotsman
Addict
Rennlist Member
 
the flyin' scotsman's Avatar
 
Join Date: Oct 2004
Location: Southern Alberta, Canada
Posts: 10,618
Likes: 0
Received 0 Likes on 0 Posts
Default

the roll pins locate the tbelt cover......take it off and inpsect as well as the rotor
the flyin' scotsman is offline  
Old 11-17-2011, 06:33 PM
  #8  
porschevert
Addict
Rennlist Member
 
Join Date: Sep 2010
Location: Raleigh, NC
Posts: 79
Likes: 0
Received 0 Likes on 0 Posts
Default

FOUND THE PROBLEM! This engine must have come from another car that had been in a pretty serious accident. This is incredible but the block has a repaired crack (welded) all the way around the bell housing area! That was the first clue. To find out why the dist. cap was getting scored as described above, we removed the T-belt, cam sprocket and right side rear half of the T-belt housing, cleaned it, and noticed the crack. This was evidently caused by a frontal impact of the engine. Who'da thunk it!
porschevert is offline  
Old 11-17-2011, 06:47 PM
  #9  
Mrmerlin
Petie3rd
Rennlist Member

This Post Sponsored by:
Dow Corning« & DeoxIT«
 
Mrmerlin's Avatar
 
Join Date: May 2004
Location: Philly PA
Posts: 22,749
Received 3 Likes on 2 Posts
Default

This thread is......
Mrmerlin is offline  
Old 11-17-2011, 06:49 PM
  #10  
Bill Ball
Under the Lift
Lifetime Rennlist
Member
 
Bill Ball's Avatar
 
Join Date: Mar 2002
Location: Buckeye, AZ
Posts: 18,482
Likes: 0
Received 0 Likes on 0 Posts
Default

...useless without...



Wow! I'd like to see pictures of that.

So, is the current problem due to the weld bead holding the backing plate off kilter? The bellhousing is a long way from the cam nose.
Bill Ball is offline  
Old 11-17-2011, 06:52 PM
  #11  
SeanR
Running up the Odo'
Rennlist Member
 
SeanR's Avatar
 
Join Date: Apr 2006
Location: DFW Texas
Posts: 34,618
Received 13 Likes on 11 Posts
Default

Yea, i wanna see some pictures of this. Very odd.
SeanR is offline  
Old 11-17-2011, 08:58 PM
  #12  
ROG100
Addict
Rennlist Member


Rennlist
Site Sponsor

 
ROG100's Avatar
 
Join Date: Jan 2003
Location: Double Oak, TX
Posts: 15,720
Likes: 0
Received 2 Likes on 2 Posts
Default

Ray,
Having seen pictures of the crack on the rear cover it does not look like it would move. If it is cracked it may also be bent out of shape causing the misalignment of the cap.
Roger
__________________


Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014

928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
ROG100 is offline  
Old 11-17-2011, 09:52 PM
  #13  
Imo000
Captain Obvious
Super User
 
Imo000's Avatar
 
Join Date: Aug 2003
Location: Cambridge, Ontario, Canada
Posts: 21,228
Likes: 0
Received 5 Likes on 4 Posts
Default

It's also possible that they just dropped the engine when it was out of the car.
Imo000 is offline  
Old 11-17-2011, 11:43 PM
  #14  
NC928S4
User
Thread Starter
 
NC928S4's Avatar
 
Join Date: Jan 2011
Location: Cary, NC
Posts: 655
Likes: 0
Received 0 Likes on 0 Posts
Default

So this is my car and I have pictures. In addition to the "crack" in the photos the back plate is also bent slightly from who knows what of the various POs. At first inspection using 50+ year old eyes you don't notice the bend. The deflection/bend is very minor as evidenced by the wear pattern on top of the rotor. The left side rotor which works perfectly has a "point" wear pattern whereas the problem right side shows a 3/32" diameter circular pattern(no photo until next week). This pointed to an off center distributor mounting. So splitting the diameter of the wear pattern as the offset of rotation it didn't take much of a bend from approximately 3 inches away on the backplate to cause the mount point of the distributor cap to be off.

Anyway, 928intl has replacement back plate and front cover on route. Thanks Mark, for extending the 50% holiday discount before the special actually started. Also, thanks to Roger for extending new parts to isolate the problem. I have NOT had this much fun and expense since my last root canal.
Attached Images   
NC928S4 is offline  
Old 11-18-2011, 02:20 AM
  #15  
Bill Ball
Under the Lift
Lifetime Rennlist
Member
 
Bill Ball's Avatar
 
Join Date: Mar 2002
Location: Buckeye, AZ
Posts: 18,482
Likes: 0
Received 0 Likes on 0 Posts
Default

So, crack in the block, welded, as well as a crack in the backplate. Wow.
Bill Ball is offline  

Thread Tools
Search this Thread
Quick Reply: Badly Scored Distributor Cap - Help 1989 S4


Contact Us - About Us - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: