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One problem at a time

As the title says I'm picking away at small problems on my 83 sc one at a time.

I had the CDI box rebuilt and the vehicle seems to be running real nice now. I'll put a timing light on it once more to confirm but I suspect it is good.

I am somewhat concerned about the low oil pressure at idle with warm engine but after reading a couple of recent posts it appears the problem will be corrected by adding restrictors in the oil lines to the cams. I'll take care of that shortly. With 182K mi. the oil pressure at running speeds is very good.

I am now experiencing, more and more, a very erratic tachometer. It's bouncing all over the place. I dare say it's probably a bad/weak connection somewhere, but where to start.

Do any readers have a suggestion as to where I might start?

Also, Have any of you gone thru the trouble of finding all major ground points on the vehicle and completely re-doing them? It sounds like a smart thing to do with no real downside.

Thanks for the help,
Hughc
Old 07-07-2017, 08:43 AM
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for the tach, I would check your multi-pin connections in the engine bay. One at the very back by the driver's side rear corner, and the other by the rear shock mount. The one that is in the back corner came slightly loose on mine and bounced the tach around. And when it completely falls off, the car dies!!! I'd start there. And I'd recommend unplugging it, and then plugging back in. I also put silicon grease on my plugs.

I did go through the more difficult ground straps when I had the engine/tranny out. Engine to alternator, Engine to body, etc. Haven't done the easy ones yet!

Let us know if this helps!
J
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Old 07-07-2017, 08:48 AM
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^^^ Good advice.

Also be aware that a bouncing tach is also a symptom of a bad VR that is overcharging the battery. Good idea to invest in a $10 Innova voltmeter that plugs into the cigarette lighter so you can keep an eye on battery voltage. If you're seeing voltage spikes at the same time your tach is bouncing, then that is a dead giveaway.
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Old 07-07-2017, 08:58 AM
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also a bouncing tach is a sign of a .... bad tach ....

if it is swinging wildly after a shift your damping is gone and it likely needs a repair or rebuilding.
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Old 07-07-2017, 10:08 AM
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Since you had the CDI box out, its connector is as good a place as any to look for a loose tach wire. One of them sends the tach the signal.
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Old 07-07-2017, 11:10 AM
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Quote:
Originally Posted by tirwin View Post
^^^ Good advice.

Also be aware that a bouncing tach is also a symptom of a bad VR that is overcharging the battery. Good idea to invest in a $10 Innova voltmeter that plugs into the cigarette lighter so you can keep an eye on battery voltage. If you're seeing voltage spikes at the same time your tach is bouncing, then that is a dead giveaway.
This is a good idea.

I am not sure what the level of voltage variance is to cause disruption, but when a v-reg is working it's within hundredths of a volt given a certain load/rpm.

Mine would bounce two tenths to half a volt at idle before changing the v-reg. Probably was worse in driving conditions?
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Old 07-08-2017, 04:55 AM
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Originally Posted by hughc View Post
Also, Have any of you gone thru the trouble of finding all major ground points on the vehicle and completely re-doing them? It sounds like a smart thing to do with no real downside.
I think a lot of us have had to do this. Once you get your tach problem sorted out this is a good task. It is not a lot of fun though.

My advice is to get acquainted with the wiring diagrams. There are good diagrams in the back of the Bentley if you have it. There are diagrams that show all the ground points. Two big priority points should be the two main chassis grounds (other end of the negative battery terminal and the the transmission ground strap).

After you do that, it is a good idea to go circuit by circuit cleaning the fuse and relay connections. Dennis (timmy2) always advises to take a razor blade and spread the pins on the relays. That's a great tip because they can get loose. I went so far as to replace the fuse panel. One of my problems was a cracked panel that was making some of the fuses momentarily lose contact when they came loose under vibration.

Deoxit D5 cleaning spray and some emory paper are good to use.

I have had to put new terminals on a lot of connections, particularly the ones associated with external lights. Sometimes you need to get to fresh copper.
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Old 07-08-2017, 06:22 AM
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Thank you for all the replies and suggestions. I won't be doing any checking for at least a week since I'm off on a motorcycle trip but I will keep you informed once I check a few things, such as the VR.
Old 07-08-2017, 07:27 AM
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grounds are a VERY smart thing to do and very often over looked.

check charging for tach bounce if grounds don't fix it
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Old 07-10-2017, 06:53 AM
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Well I finally got a 12v cigarette lighter meter, plugged it in and went for a drive.

The volt meter was indicating 14.2 v around town but once on highway it indicated 17.2 and even a bit more. That doesn't sound right to me.
The tach started bouncing around after about 50 mi. and the voltmeter was indicating 18.3v, so I suspect there may be a problem with my VR.

I did manage to clean the chassis ground on the strap that goes to the transmission but not the transmission end as it was impossible to get at. Will have to try that again once I get the vehicle a bit higher off the floor.
I also cleaned the body ground on the battery neg terminal and the one behind the fuse box in the frunk.
The others will have to wait for a more convenient time.
Anyway, at this point I'll have to find out what the maximum voltage should be from the VR and take it from there.
Cheers
hugh
Old 09-15-2017, 01:59 PM
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Quote:
Originally Posted by hughc View Post
Well I finally got a 12v cigarette lighter meter, plugged it in and went for a drive.

The volt meter was indicating 14.2 v around town but once on highway it indicated 17.2 and even a bit more. That doesn't sound right to me.
The tach started bouncing around after about 50 mi. and the voltmeter was indicating 18.3v, so I suspect there may be a problem with my VR.

I did manage to clean the chassis ground on the strap that goes to the transmission but not the transmission end as it was impossible to get at. Will have to try that again once I get the vehicle a bit higher off the floor.
I also cleaned the body ground on the battery neg terminal and the one behind the fuse box in the frunk.
The others will have to wait for a more convenient time.
Anyway, at this point I'll have to find out what the maximum voltage should be from the VR and take it from there.
Cheers
hugh
Yes, it is the VR.

Not a fun task on the 3.2 cars.....

Gerry
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Old 09-15-2017, 02:38 PM
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I'm not a fan of oil restrictors on the cam feeds. If your oil pressure is fine while driving, leave it alone.
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Old 09-15-2017, 03:50 PM
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Quote:
Originally Posted by RSTarga View Post
I'm not a fan of oil restrictors on the cam feeds. If your oil pressure is fine while driving, leave it alone.
With your concern over low oil pressure, I would change the oil up to a high-quality thicker grade product, especially in summer.
Old 09-16-2017, 03:57 AM
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Very, very, very frustrating. Things just seem to be going from bad to worst.

I removed the alternator from the vehicle and had both it and the VR checked by a professional shop and they both checked out OK, although I was told the brushes on the VR were wearing quite badly. The alternator was replaced app 20K mi ago, according to work records but I was also told the slip rings were noticeably worn.
So with the alternator and VR checking out OK that system can probably be eliminated as the cause to the fluctuating tach, but I do have a new VR on the way and will install it as I receive it.

What's even more frustrating now is that the engine is shutting of as I drive it. I went for a drive today and the engine quit at least 8 times. In every case I just had to turn the key off and restart the engine, no problem. Twice I pulled over and came to a stop, did not touch the key, just left everything as is, then with a voltmeter I verified that there was 12v to the FP relay and that was good. What I neglected to notice was whether or not the fuel pump was running (before I removed the relay). As it turned out I replaced the relay and the car started immediately.

So there appears to be an occasional electrical glitch that is causing the engine to quit, but where to look.
As mentioned earlier in my post the CDI unit was recently rebuilt by Bob Aschroft so I don't suspect that unit but I suppose any related wiring might at fault.
Any and all suggestions will be appreciated.
Thx
hugh
Old 10-01-2017, 12:31 PM
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Don't drive the car while it's putting out 18v you can ruin a lot of things possibly even burning it to the ground. I would check the water/acid level in the battery because it may be boiling away (the water that is), acid doesn't evaporate.
Old 10-02-2017, 07:50 AM
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I can't understand why the digital voltmeter was initially indicating 18.6v.
As previously mentioned, I removed the alternator and both it and the VR checked out OK, so I am at a lost as to why the voltmeter would read as high as 18.6v.
It may be a faulty voltmeter from the manufacturer so I now carry my shop voltmeter with me and if the digital meter again shows an extremely high voltage I can double check with the shop meter.
I'll keep you informed of any developments.
hughc
Old 10-02-2017, 12:47 PM
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hugh,

Back a few years ago I had a lot of electrical gremlins. I had all the symptoms of a bad VR. I too had it tested and was told it was good. I replaced the alternator and VR because I simply could not believe I could not have a problem. I posted about it here. Some people suggested that a fail-ING unit could fail intermittently. I decided to replace both for good measure and never had another problem.

Interestingly enough, my CDI also failed around the same time. Something that has been discussed on here before is that some CDIs can be susceptible to over-voltage. I am not a EE and do not pretend to be one. Coincidence or correlation? Hard to say.

As gomezoneill said, if you are getting big voltage spikes and using a conventional lead acid battery, be very careful!
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Old 10-02-2017, 02:32 PM
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Thank you Tim, I do have a new VR on order and I will be trying it as soon as I can. I really can't spring for a new alternator at the moment and hopefully I won't have to.

Of course the other problem that is annoying is the sudden shutting off of the engine while driving. The engine re-starts immediately, which is good, but the problem has to be addressed. I do have a competent friend that will study the electrical dwgs. and suggest where I should look.
It really is odd that these problems should surface all of a sudden when all along the vehicle was running fine.
I'll update when I can.
hughc
Old 10-02-2017, 04:07 PM
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fix the alt problem first and see if it is related to it cutting off.

when it cuts off do any dash lights come on
spin the fuses on the fuse panel. could be bad connection
CD unit. they fail when they get hot, yours may be going bad, but there are still other things that can cause it
coil, same as CD, heat. they fail when hot and can work again when cooled off..
green wire from dist. wiggle it around and see if it cuts off.
bad ign switch.
FP relay
FP

this may be one of those things it ahs to get worse before you can figure it out....usually involves being towed.
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88 BMW 325is 200K+ [__] RUNNING: [__] NOT RUNNING:
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[] RUNNING:[_] NOT RUNNING:__2000 MER E320 WAGON [_] WRECKED:[]RUNNING:
Old 10-03-2017, 03:50 AM
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Hugh, sorry I can't add anything to the electrical/cutout discussion, but can for the oil pressure. From what I recall, it states right in our owner's manual that oil pressure can drop to almost zero at idle, and to not worry about it. As long as it is good at speed, you should be good to go.
Good luck finding the cutout problems,
Craig
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Old 10-03-2017, 11:20 AM
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