OzGemini.com

:: Holden Gemini Forums
It is currently Sat Dec 15, 2018 12:18 pm



Post new topic Reply to topic  [ 3 posts ] 
Author Message
 Post subject: Rare problem - experience may help others
PostPosted: Mon Nov 12, 2018 11:32 am 
Offline
Long Term Member

Joined: Tue Apr 10, 2007 3:46 pm
Posts: 1855
Location: Brisbane
About 2 months ago my son came round in his coupe and when it pulled into the driveway I noted that it was running on three cylinders at idle. Asked him how long it had been like that and received the expected answer of “like what?”. It was only missing a cylinder on idle and was otherwise running beautifully. Pulled off some plug leads and quickly established number 4 had gone missing. The fact that it was cruising well eliminated head gasket and valves, crook plug lead and plug were possibility but since high vacuum cruising was OK probably not.
Spark plug on Number 4 was a lighter colour then the others indicating leaner mix on that cylinder. Aha!- manifold air leak says the front part of my brain. The booster draws on number 4 so checked that and the hose for leaks. Both had been recently renewed so no problem there. Sprayed some carby cleaner (flammable) on the manifold flange and momentarily. Right, crook manifold gasket says the front half of my brain, but the back half, that I ignored, said “why now after 7 years of running perfectly”.

Fix Attempt 1 – empty radiator, pulled off manifold, installed standard new gasket, put back together. Still running on three.

Fix Attempt 2 – same as above, thicker gasket and sealant. Still running on three.

Fix Attempt 3 – Must be a problem with the manifold face or a crack (Lynx single side draft manifold) says the front part of my brain, the back half doubts that this is problem that suddenly developed after 7 years. I have a spare! Same fix as above but with 45 dellorto mouted on a new manifold. Still running on three.

By this stage the weekend has come to a close and I am over it. Give car back to son. A month goes by.
Fix attempt 4 – same as above, check all surfaces again, file any potential clearance locations, with new gasket and super doper sealant. Tighten slightly, allow to cure overnight and torque to spec. Still running on 3.

Fix attempt 5 – spray the carby cleaner on the flange and again briefly runs on four. I am thinking crack in the head inlet port? Imperfection in head face?. The back part of my brain does not credit any of this but the front half grabs the surer doper sealant and smoothers the joints of the flange and head – leak now you bastard! Still running on three.

Dejectedly I resolve that the head will probably have to come off and be machined. So I drive the car back to my sons place, still cruising beautifully and note the temp gauge has not moved. Must have dislodged in the frenzy of manifold goo ing. Arrive at sons, pop the bonnet to reattach sensor wire and note the vacuum advance hose off. Strange I think, that should have made more impact than it did on top of the other leak. The vacuum advance is connected to the fitting for the booster on a take off for the vacuum gauge – so full vacuum set up not carby vacuum. I pinch the hose and engine note changes. Hmmm, goes the back of my brain. I place the line on the dizzy connection and suck – no resistance. Diaphragm in vacuum unit obviously stuffed.
Now the front half of my brain catches up. The advance diaphragm is right up against number 4 manifold port in a 4ZC1 so the carby cleaner I was testing with was being sucked into the hole in the Diaphragm and into the engine, not through a gap in the inlet manifold. There was never anything wrong with the manifold seal.

Fix attempt 6 – plug vacuum hose, adjust idle mixtures and speed screws, took 5 minutes. Running on four.


Top
 Profile  
 
 Post subject: Re: Rare problem - experience may help others
PostPosted: Fri Nov 16, 2018 9:53 pm 
Offline
Long Term Member

Joined: Sun May 13, 2007 9:34 pm
Posts: 1233
Location: South OZ
I feel your pain :)

_________________
http://www.ozgemini.com/forums/non-tech ... hp?t=26329


Top
 Profile  
 
 Post subject: Re: Rare problem - experience may help others
PostPosted: Mon Nov 19, 2018 10:32 am 
Offline
Regular
User avatar

Joined: Mon Oct 05, 2009 8:28 am
Posts: 442
Location: Newcastle -32.872095,151.707064
Cool story. Always learning....

_________________
"Nothing f*cks up your Friday more than realising it's only Tuesday..."


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 


Who is online

Users browsing this forum: No registered users and 4 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron