effects of battery disconnexion ?

[fatbloke-dim]

As the ECM off my ' 93 has gone for re-man ,the battery has been disconnected for a few weeks . Does anyone have any idea if this would cause any issues with any of the systems on the car ?

On another note , I was checking a few earth/ground connexions just to make sure everything there is as good as poss ,and I came to the maxifuse box behind the battery ,and noted a 20Amp fuse for the ECM . Thought I'd check it out , see if the fuse was sound , as the fault had been of an intermittent nature . When the fuse was pulled , there was a deposit of some pinky-white powdery stuff on the blades of all the fuses in there , something like dried toothpaste , or the kind of plaster you'd skim an interior wall with . Hmmmmmmm.....None of this was evident in the other fuse block in front of the battery , and where the stuff was , on the blades of the fuses , it looked like contact was , or had'nt been too good for a while . I cleaned them , got them all shiny-nice , and inserted and removed them a time or two to try and get the blade slots a bit cleaner , assuming that this stuff was in there , too . Does this sound familiar to anyone ? The deposit did'nt appear to be corrosion - related , the fuses cleaned up with no pitting or any other wear to them . Just wondered if there was ever any material applied at the factory for any purpose ? Most peculier .

 

[boomdriver]

Should not be an issue. The ECm memory will be wiped clean, certain performance values will have to be re-learned thru driving, and the radio stations will have to be reset.

As far as the crud on the fuses, thats probably oxidation from the sulfuric acid fumes from the battery. I would not count that out as a source of trouble. EVERYTHING on the Corvette is managed and communicated thru electrical resistance or low voltage signals. When corrosion gets in the way, those signals can be altered and cause all form of trouble. Try to seal the fuse box as well as possible and make sure the battery is clamped down so it cannot move and spill any liquid out that can get onto sensitive electrical parts. Why engineers would place fuses or other things near a battery is beyond me. All wet cell batterys have acid and its very corrosive to conductive metals and wiring. In a perfect world they stay sealed and don;t leak. My world have never been all that perfect...:eyerole

 

[fatbloke-dim]

HAH !!

My world would be no better , and possibly a fair bit weirder..... Thanx for the info about the battery , I feel a bit more relaxed that that at least should have not added it's own share of woe to the gremlins . There were no radio stations set , as far as I know , I personally have'nt even driven it yet , after owning it for 2 and a half weeks , due the dead or dying ECM. There is only one station I ever listen to , but that won't get a look-in if the car is fixed - I'll be too engrossed with the sweet sound of Chevy .There's no evidence of any acid leakage/spillage , and everything in there is clean and tidy , and the battery is cinched down tight . Sometimes , you see the grief these things cause ,all over the forums , and you get to thinking these cars have a life of their own , known only unto themselves , so , I dunno , maybe it was dried ectoplasm .........


Just got an email from Davies Corvette , the ECM is ready to ship , great timing as the weather here has nose-dived into early wintry-autumnal crap , certainlynot drop-top weather . Our climate here sucks ! Thanks again , Boomdriver !

 

[fatbloke-dim]

back on the road !! WOOOOHOOOOO!!!!

Well....

after the customs folks dragged their heels , and the postal Johnnies did their bit , I finally tracked down me old ECM. It was in the Manchester sorting office for a few days , eventually a notification from USPS arrived at my inbox saying it was held for notification of charges payable . Via "snail-mail" . So , I called the Parcelforce helpline , eventually getting someone to speak to - a real , honest-to goodness - genuine human. "Can I short-circuit the notification process and call at the office ?" sez I . Sure . Off I dashed , the office being only 10 minutes away , longest 10 minutes of my bloody life , that was . I was sure there'd be some hiccup or cock-up , it all seemed too easy . There was a notice up in the office saying packages can't be collected until notification has been documented , so I thought that was where things would fall apart . The upshot was that I got the ECM , paid the import , taxes , etc. , - less than I'd figured too . Half an hour later , it was back on the car , the ignition turned on , all dash lights lit up for the power up test ,went out , and no fans started . Looking good . Started right up , correct idle where previously it was idling at 15-16 hundred with both rad fans on .
When warm ,it idles rock-steady at around 450 .Sweet . went for a short run , maybe 2-3 miles , and at one stage there was some popping in the exhaust , sounded like in the front end of it , under acceleration , occasionally a little bogging , under a full boot full . Went like stink if you were a bit more thoughtful about putting the boot in . Hoping that may just be crudded o2 sensors that need a good blow out , or that the brain just needs a little time to re-learn things .

And the weather is getting unseasonably warm by mid-week , so somethings gotta give !

 

[Hib Halverson]

With 84-93 ECMs, when you disconnect the battery, fuel trim values the high/low octane spark table selection and a few other characteristics which are part of the engine controls self-learn capability are lost.

The next time the engine runs it takes several miles of normal (not aggressive) driving to "relearn" most of those characteristics. Driving the car hard will not restore those characteristics in as short a time as will driving in normally.

As for the corrosion on the fuse, on a car that old, it wouldn't surprise me that builds up. It might be due to moisture. It might be due to a bad connection...it could be a lot of things but you did right in cleaning the fuse blades. Better is to spray the fuse block "slots" with contact cleaner and, if you can find an old fashioned point file. First, disconnect the battery, then slip that into the fuse blade slots a few times to abrade them.

You didn't say why you had the ECM "rebuit", but high resistance/bad connection due to corrosion in the fuse holder for the ECM fuse could cause false diagnostic conclusions.

 

[fatbloke-dim]

Ecm fixed , now the battery/charging is having a go!!

Thanx , Hib;-

The reason for the ECM re-man was that things were scatty with the idle and rad fans , fans were on at ignition power-up with the engine cold , the idle was about 15-16 hundred . Some times , this would settle when things were good and warm , but then if you just gently tap the ECM box , it would go beserk again , or if it was already beserk , it would settle . When the "new" ECM was fitted , everything was spot-on from then , apart from the aforementioned sputtering and popping . I am seriously happy to report that after a couple more miles ,this has all cleared and it now runs very strong and sweet , and correctly , so I reckon the ecm was dead or dying . HOWEVER.........

Since giving it a good run last night , there's a battery drain issue , the car made it home on a tow truck , again due to a flat battery .

Here's how it went ;-
Copped an unseasonably pleasant evening on Sunday , so went for about a 100 mile run , ran like a new 'un . whoooooohhooooo!!! However......on the motorway , about 2 miles from home , it spluttered briefly and picked up , then jossed it completely . Watched the hazard lights slowly give up the will to live in about half an hour waiting the AA recovey truck . The batt light was on just as the engine was dying, and I'm fairly sure the voltmeter went from abut 14 when I set off to about 10 by the time it choked . Seems like there's a drain somewhere or the charging is'nt happening , I don't think the batt is dead , as it takes a charge ok , and there's no batt warning /charge light up when running . I don't know if there's anything left switched on , I'll have a check , there's no lights on , no interior lights , sunvisor lights , radio - nothing . The passive keyless thing is active , and there was a light for that , but that might have been whilst the key was in the ignition . When you reconnect the battery , there's some clicking of relays going on in the front left engine compartment , near the side of the rads , or behind the left headlight . Don't suppose you have any idea what that might be ? Have'nt got me manuals yet , so not sure what's down there , or if it should be clicking anyway . Sometimes hear a little crackle of arcing when the batt leads go back on , too .


Any road , the brain seems fixed , that's a relief , so now time to track down this electrical gremlin . Better get the charge rate checked and see if there is a drain on going somewhere .



More news as it breaks

Any how , thanks for all the assistance , what a great resource this forum is !
Cheers for now,
Nigel H.

 

[fatbloke-dim]

further frolics !

. Just spent a few hours with a multi-meter trying a parasitic load test , which was'nt conclusive , other than current leakage is minimal . The clicking under the hood is from the left headlight motor , when you pull the main lighting fuse it does it , and still getting quite a big arc when connecting the battery . Might be there's a limit-switch in there , needs setting properly . I will try to get the battery tested tomorrow, and see i the charge/discharge numbers are correct . If this car were a locomotive , there'd be a battery charge fuse , and that would be the first port of call , but is there anything that performs a similar function on a C4 'Vette ?

Nige .
​

 

[malc350]

Check the battery connections are tight - mine displayed extremely strange behavior and then didn't start and it as down to the battery negative not tight enough.

The clicking from the headlight area is normal. I think it's just a relay. The other sounds also are normal. Your voltage sounds OK except the low one. Mine doesn't like to start when volts are below about 11.5 though a new battery has cured this.

Also alternators can be weak on these cars - mine shows up to 14.4 volts when driving and about 12.5 before starting. My battery is quite new due to the negative post breaking off my previous battery (due to a rusty terminal bolt which was so tight I broke the terminal post off when I undid it..)

Also worth checking the connections on the starter. I had a loose one there on my Callaway that gave all sorts of grief until I found it.

Alternator problems seem to follow battery problems hand in hand, at least on my C4s...

Regards, Malc, also in the UK

 

[fatbloke-dim]

Malc350;-

Hey up mate .Thanx for your angle on this ! The click is defo from the headlight motor itself , but I am of the opinion that it may be quite normal . The healthy arc drawn when connecting is a bit odd , I'd have thought , there should'nt be a lot on line except the alarm , PKE and clock , as far as I understand things . Could be the battery is kaput, it's age is'nt known , it be one of those sealed for life Delco jobbies , with a green bead that - I think - should rise up under a little lens in the battery top to show charge , or it shows either black or wwhite to show discharged or f?%&*D . Forget which way round the black/white thing is , one way or 't other . Any way , the green ball is down at the bottom of a tube , it appears , near , or on the top of the battery plates . You need to squint down in there to see it . Anyone else have any clues as to how this particular indicator should appear if all is well ? Or not . Should that little green ball be at the top , right under the window ? Could just be a new batt is called for , but that'd be too easy . Have got a sparks coming round tomorrow to see if he can nut out any drain at rest that may be sucking the life out of it . The guy I bought the car off always had an Optimate connected , not because it was troublesome , it was something he's always done with his fair weather cars . I've been told a Vauxhall Zafira battery fits . Anyone know about this ? , Side terminal batteries are'nt common over herein the U.K. , but are likely available from American specialist suppliers , as likely will be alternators if required . There has never been a starting issue with the car ,'cept when the battery was flat ,an overnight charge fixed that , tho' .

The saga continues , just as we get some ace wether for top-down cruising .........ad