427 runnin trouble

Hey guys, I just recently bought a 1968 Corvette with the 427,4spd,MSD ignition. Once I charge the battery the car will start fine and it will idle but once you put a load on it (tap the brakes, turn on the
turn signal the car will die. No matter what I am revving the car at. I am new to the Corvettes. I'm normally a Ford man but I got a hell of a steal on this car. The previous owner replaced the battery,ground wire for the battery,voltage regulator and the alternator. Any help is greatly appreciated.
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Sorry can't be of any help (sounds like fuel prob). Glad to see the old 68's are still around, I used to own one until the first kid came around. Loved that car....Ya' say you got a great deal.... My window sticker back in 68 read $5,300 and that was for the 427. Good Luck and enjoy....BC
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Joe wrote:

ignition with the turn sigs running. Any variation over 0.5 volts is a clue. Measure from the "cold side" of the MSD system back to the negative battery terminal -- zero volts (if not there's a grounding problem).
If there's a hot-side problem look for an error in wiring to the MSD -- someone leave a ballast resistor in the circuit? (That would explain the easy start). Face facts-- a 35 year-old ignition switch might not be in the best of shape. If that proves to be the weak link, consider installing a relay to control full battery voltage from a fusable link at the pos battery terminal to the MSD. Old ignition switch can hack the relay with no sweat.
Finding an old ballast resistor can be a problem--rather than using a firewall mounted resistor like Chrysler and Ford did, the early Chevy ballasts looked like fusable links.
Best of luck.
-- PJ '89 Hookercar '02 e-blu coupe
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On a wild guess, it sounds like a two-fold problem.
It sounds like the battery is shot and the alternator is not working.
If you have to charge the battery to start each time, it sounds like it is not holding a charge. Try starting the car, shut it off, start the car, shut it off, and finally start again. If it can't start it three times in a row, the battery is toast. Each time you start, check the amp gauge. It should be showing a fairly large positive charge, since this isn't a new battery and fully charged. If not, your alternator or voltage regulator has a problem. It could be as simple as the VR is stuck after a few years of sitting.
Measure the voltage on the alternator hot terminal. It should be about 12 v or so not running, and about 13.5 v while running.
You can also take the battery out and try it in another vehicle, although starting a 427 cold is about as hard as you will come across.
I'm not fond of MSD. The stock system works find for 95% of the driving or more. Too many "electrical experts" install systems like this in their cars and things begin to not run right.
Check the grounds to the engine. There should be several ground wires from the engine/transmission to the frame. If not, take a battery jumper cable, clamp a black to the alternator bracket and a red to the intake. Then clamp the other red and black to the frame. See if the problem goes away.

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If the alternator works, you should be able to start the car, disconnect one of the battery cables, and the engine will continue to run. If the engine dies when you pull off the battery cable, then you know that the alternator is defective. Don't reconnect the battery cable when the engine is running. Just turn it off and then re-connect.
Also, if you have a meter, you should see at least 14 volts at the battery when the engine is running & the cables are connected to the battery.

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My training was to never run an alternator car without a battery and not to do this battery disconnect test. This is the first time I have heard the caution not to reconnect a running alternator. Please comment or supply further information.
TIA
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I'm sure the type of alternator has a lot to do with it being safe or not.
1963 to 1968 - external mechanical voltage regulator. I can attest you can do this without the alternator going belly up.
1969 to 1980s (depending on vehicle) - not a great idea, but you can probably get away with it for the disconnect. I'd shut off before reconnecting.
1980s to 1990s SI alternator - my experience has been it is hard to keep it living under normal conditions, I' never try the disconnect unless I had a lifetime warranty on it. In fact, all you have to do is take a trip and be 100 or more miles from home and it is sure to die. Delco must have farmed this one out to Lucas.
The electronic voltage regulator alternators are sensitive to large voltage surges or pulses. The worse thing you can do I have found is to jump start a car with yours running. As the dead car cranks, voltage is pulled way down, with heavy current drain. As soon as the dead car starts, the voltage spikes, and then the alternator of the dead car also spikes back into the jumper car, so you really get zapped hard.
Odds are the regulator will go south and in a couple of months, your battery is dead, not holding a charge, because the alternator has either been undercharging it or has been charging with only one or two phases of the three phase current an alternator produces.

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Thanks Tom, that is pretty much my opinion also.

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Sounds like you may have multiple issues that need addressing. First the dead battery issue. My advice is this, first with all accessories off and all doors shut and any accessory that could draw a load, phone adapters ,cigarette lighter plugs etc removed, pull the negative cable off and insert a test light or a cheap radio shack meter that measures amps -in line- with the cable. An amp meter will give a better indication of what is going on but if the test lamp is used and the light is lit bright you have a draw on the system which over time will kill the battery, to isolate the draw, start with the alternator plug and main cable to the alternator and disconnect one at a time while the test light/ amp meter is installed..when the lamp goes out you have isolated the problem, of course this only finds it sometimes if it is alternator related from a bad diode. (2) if this fails to locate the draw then the next method involes a bit more time. Slowly pull one fuse at a time to isolate which CIRCUIT is the draw occuring on such as B/U Turn circuit which could be either or. This will help determine and narrow the trouble making circuit. (3) earlier cars had issues with clocks especially analogs that quit working mechanically but that would still draw amperage trying to run, in that case it is either disconnect the clock or replace it. (4) if the draw still exists look to the battery and see if there are any other things that are wired to the positive post such as MSD, AMps for stereos etc. then remove those leads one at a time remebering to hook the positve cable up tight and recheck for the draw. Stereo hacks are good for hooking up all kinds of crap to the battery and some not properly causing amps to stay powered up all the time etc. Also while we're on that subject alarms and car starters are sometimes ghost issues as well. ( Having fun yet)
Having the battery tested is also a good idea seeing that killing a battery stone cold dead on a few occasions pretty much destroys them, and if you can add water to it..well in my experience, especially on a Vette where the battery is in a less than desireable area to service is a waste of time and money. Buy a Delco completely maintenance free and be done with it. I don't know about you but changing batteries on Vette's needs to be a once every 3-4 year project not every year, plus trying to stop acid leaks and corrosion due to water puking sucks too.
Battery cable ends also should be a crimped or soldered thing not a 1.50 temporary bolt together p-o-s.
The simple things seem to be more overlooked which fix more problems than I can tell you.
As far as the MSD unit goes and the quitting, the MSD is awesome, couldn't ask for better ignition however, BE Careful! This thing will bite you bad. IF you have a bad wire etc. you'll find it the hard way...OUCH.
The MSD unit should have it's own power and ground and the case of the MSD does NOT have to be grounded to work properly. Most race application MSD's have a rubber mount to isolate the unit from severe vibration and hence it's own ground. Since wiring one of these can take some time to be done right, I would suggest downloading the instructions from MSD/Autotronics and verify proper connections especially the Main power and grds which in my opnion should go directly to the battery due to loads placed on these by the unit. If you find these wired to a fuse panel or such remove and follow the installation instructions to correct.
My suggestion on that is to get a digital voltmeter and connect the voltmeter to the engine block then back to the battery negative terminal when you are performing this stalling issue. Anything more than .2-.5 volts indicates a bad ground and will cause issues. Seeing the old vette is glass grounds become super important to prevent feedback and weird related issues. I would also find where the interior grounds back to the battery go and are connected properly to the engine etc. The chev's used to use a strap from the operators compartment to the rear of the cyl heads to properly ground the body to the block back to the battery and like wise sometimes used a ground from the frame to the engine or battery due to the rubber body mounts.
Check them all.
Sounds like a poor ground to me, you could setup a temporary ground using a jumper cable to verify your concern also cutting the diagnostic time down even more.
As the other gentleman said it may be a poor ignition switch, but the battery may not be able to keep up with the load that is being placed on it by the igniton and other things.
Charging voltage should be 13.5-14.7 volts and nominal voltage should be 12.6 volts if not the battery is either no good, bad call or not charged fully.
Like I said previously if it has been killed dead multiple times replace it with a Delco and start the search from there. Never ASSuMe anything when diagnosing. Follow these steps and it should provide you with a genuine cause, that you can fix to resolve the issue instead of throwing parts at it.
If this is going to be a car you drive a lot spend the time and do it right.
Ps: A bargain Corvette is better than any Ford any day!
Thanks,
James D
Master ASE tech

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