Let me tell a little story that happened to me and it might be educational to other members too....
Well , as you all know or remember , i have recently updated my engine , from 1.5 to 1.7 . Along with little tuning * porting etc , i have additionally restored my Marelli distributor back to life plus i have installed 10mm silicone spark plug cables. All other remained the same and untouched from 1.5 . New engine was removed from a daily working 33 fully serviced recently and well known for its conditioned. Only negative issue for me is the fact that was an IE version which meant slight differences on cams and compression but this is not so important after the installation of carbs.
Couple of details that are crucial for the rest of the story , i had a Weber
battery of about 4+ years old and a safety pin on negative pole for quick release as with old cars you never know when you will need to disconnect current fast. Also sparks were Champions which were removed from a GTV 916 with only 10k miles on them ( dont ask why .....) in excellent condition.
Now , lets start with our story......
From day one it was obvious that the new engine was excellent as described with no smoke at exhaust and lots of torque at low revs . On the other hand , it lacked performance at mid and high range but I thought it was due to carb setup as they were tuned for a slightly tuned 1.5 . Thats why i was looking for needles and venturi tubes to fix that problem. Another thing that I noticed was that when starting the engine , it turned very slowly but with the 2nd turn it would fire up since the 10mm cables were more than great and could deliver a very strong spark.
After a couple of months , around January , I started to have real trouble starting the engine at random times. First it started only at morning with humidity but with a little push it would fire up immediately. Then , this would happen at more random times , even on midday with hot engine. I could drive all day , the stopping to buy a soda for couple of minutes and when trying again nothing , like the battery was drained. If i waited 5 min and tried again it would fire like the battery was fully charged.
Yes , I know what you are thinking , battery had a problem which I though also, so i went to my friends on the shop and asked them if they had a spare battery to give me which they did. It was a Varta with silver top removed from a 146 , only 1 years old and it seemed all right. As soon as we installed it , the car could start with no problem. This only lasted around a month when it started to have similar symptoms , lazy start or random empty battery behavior. I started to carry in the car a battery kick kit I had and I used it every time a could push the car
So i though that maybe it wasnt a battery issue but something else that could have wrong with engine swap , maybe a loose ground cable or even starter module as it was the one from 1.5 . I checked all wiring but didnt find anything so i focused on starter. At mid of February , car would start with kick start when occasionally happened so i went again to my friend and found a started from a 1,7 engine. We installed it an it started without problem As it seemed , starter had the problem and i thought that i had finished with it.
didnt.... After 20 days i started having similar symptoms with lazy starts or no starts at all. So it was not the starter nor the battery but something else of electrical issue. Back to the start checking everything again. I had to check every little detail such radio consumption or alternator (still from 1.5 but serviced almost a year ago) or anything else that could cause the battery drainage .
After some discussion with John (aka JKBsrpint) I decide to change the security ground pole with a steady one as a first measure in case that it could be "leaking" current. Fact is that it was a little bit loose but i didnt had any problems with it when i had 1.5 engine . Surprisingly , the car started to behave better , response was little more immediate and had less symptoms of not starting. I was on something here , maybe indeed the security pin was problematic and caused weak current.
In addition , i had some other problem with the carbs and in the diagnose progress with John we discovered that one of the sparks was probably shortcirquited and misfired causing unbalance and poor overall performance. Fortunately i had couple of spare sparks and replace it and i got some of the power back.
So I decided this weekend to remove the battery and charge it fully as I hadn't used sprint for almost 10 days. Monday morning , I installed the battery , tried couple of times and started perfectly so i was happy. So , i locked car , went inside to pickup my bag and went back to the car in order to got to work. F***k , it wouldn't start , battery was dead or had empty symptoms. Back to battery kick , plugged it in , trying to start , nada nothing , dead. Tried couple of time , still nothing , went to the engine bay and pressed the voltmeter button on the kick start in order to check the voltage.
I discovered the the voltage was around 0-2v for 30 secs and then started to rise back to 14 volts. That was strange so i went back and tried to start again. The same behavior , battery dead although was fully charged and voltmeter showed again from zero to 12v. I managed to get the gar going by pushing , went to an electrician which tested the battery and result was she was faulty. He said the Varta's with silver top had a problem from factory instead of those with black and it should be replaced. He got me a new Tudor with high ignition current
and the car started immediately and very lively. He also checked if i had any drainage through bad connection but no , the circuit was perfect.
So , 2 days after , the cars start like new and not only that , the car runs almost perfect. Lots of torque as before but now i dont have any hesitation when i push her hard up to 5.5k tpms where she slows down probably due to lack of fuel. I do get also a great kick after 3.2k rpms and leaps forward after opening full throttle. I am again excited with 1.7 as i hadnt tasted how it could performe.
Now , the final conclusion and what i suppose it happened.
Everything started from the safety negative pole on the battery. Due to poor contact I had bad charge and bad starting current. Since the engine was 1.5 it was adequate to operate although i was getting a faded red light on dashboard when using radio wipers and heater fun. Now i can understand that this was the cause and not the alternator as I thought (and was about to replace it).
After swapping to 1,7 the need for good current increased due to different compression and power ratio. By installing 10mm silicone cables I somehow managed to hide the problem with the connection as the slightest bad spark was enough to start the engine as long as the battery was good. But this was putting a lot of stress to starter and battery so eventually both started to malfunction . Not even that but things got worse by swapping with a faulty battery which would die randomly although it showed fully charged. This also caused for a faulty spark plug (and probably the rest of them are not in the best condition now). Also , every setting with carbs or Marelli ignition should be revised and reconfigured from the beginning in order to have optimum performance.
So , even the slightest details matters.......
( pfffff , that is a long post which took almost 4 hours to finish as i am at the shop right now....