70sgeek

So I'm traveling on the highway last night and suddenly engine cuts out. No loss of lights or other electrical power but car won't restart. Now when the key is turned to start position, engine cranks freely and a loud buzzer located under dash somewhere near glove box comes on.

Had car towed back to my garage and have not had opportunity to look further into this - not sure where to start but will be checking fuse box, horn relay, ignition switch, etc. Battery good, no loss of lights or cranking power.

ignition is a fresh MSD ready-to-run distributor - has been installed for a number of months now w/o issue.

any thoughts on what may be at issue?

thanks

Fun71

Is that an electronic distributor? If so, the module may have failed.
Check for voltage at the distributor power connection before other troubleshooting. No voltage = no spark. If there is voltage, check the module (if it has one)

70sgeek

Took the meter to my coil (+) - with key on on/run position, just under 5v power showing - same reading as at the IGN terminal on fuse box which is what I'm running my 12v lead from to the coil.

Battery good - showing 12.15v with everything off. - so I'm thinking ignition switch on the column shaft under dash possibly failed? Will be replacing it as time allows to see if that changes anything.

Fun71

Before tearing into the ignition switch, disconnect the wire at the distributor and see if the reading stays at 5 Volts or if it recovers. Just to make sure there's not something in the distributor loading the circuit.

oldcutlass

12.15 is about a 50% battery charge. Clean your wire terminals at the power distribution post on the horn relay and check the bulkhead connectors on the drivers side firewall.

70sgeek

I plan to work more on this tomorrow - went ahead and ordered a new ignition switch anyway but will be re-checking the wiring connections. Motor cranks well with the key but won't catch to start, as if no spark. Cranking and key-on volts are approx. 5v measured at coil or IGN lug on fuse box under dash.

will try measuring coil volts without the distributor connected and if need be, also test the distributor module - hope that isn't at issue, distributor's only a few months old

And what I really can't figure out is why a loud buzzer which sounds like it is located behind the middle dash area between radio and glove box is now coming on when key is in the run position - that's never happened before and I haven't yet been able to see where it's located to see what it's wired to. That first came on as soon as the engine shut down last night while I was at speed in the roadway. No loss of lights, horn, signals, etc all continued to function but motor shut down and wouldn't restart.

oldcutlass

You can isolate the miles of wiring to the distributor and just run a temporary jumper from the battery+ post to the coil+ terminal and see if the car starts, cranking with the key. You'll at least know that the distributor is good.

70sgeek

Distributor good - fired right up at turn of the key on bypass. Buzzer under the dash came on again though, as soon as I powered the coil up from the battery but this time went OFF with key in the RUN position.

Hoping at this point just an ignition switch replacement will make all well again...

oldcutlass

Have you checked the adjacent fuses to the IGN terminal?

70sgeek

I did and all look intact - lights, signals, horn, etc. all appear to be working. inspected wiring under dash, nothing appears visibly compromised.

Dash harness is original to the car and had never been altered - column is a 2yo reman tilt from NPD. A/C now runs on its own Vintage Air wiring harness, so at some point I may contemplate a dash harness replacement for the extra peace of mind.

70sgeek

Installed new under-dash column ignition switch (AC Delco part) and no change in status - still cranks fine but won't start at the key, reading about 4v at the IGN terminal on fuse block with key in the ON position, and loud buzzer under dash sounding like it's located somewhere between radio and glove box comes on with the key in ON position.

Inspected the ignition switch wires - both connectors and their wires look good. nothing anywhere I can see looks bad.

Engine fires right up when I bypass the coil to battery under hood - but when I bypass, the buzzer comes on immediately with key in OFF position, and goes off when I turn key to ON position.

Can't feel a buzzer unit anywhere under dash where I can get my hands, can't be the radio because that's unplugged.

Is there anything inside the column itself that could be faulty and causing these issues? Column is a roughly 2yo rebuilt tilt that I got from one of the better online vendors.

oldcutlass

Clean the adjacent fuse clips (turn sig/back up light) to the ign terminal and see if the voltage gets better.

Fun71

Just a thought - perhaps that buzzing is the mechanical voltage regulator? It is on the engine side of the firewall in the area where you say the sound is coming from.

gs72

70sgeek

That turned out to be good advice!

Interestingly, when I went to reinspect the fuse block last night I noted the t/signal fuse was blown - hadn't seen that before because fuse was mounted with the filament turned on its side. Block terminals appeared clean but I took a dremel wire-wheel to them anyway before replacing the fuse.

With battery reconnected, 12v now restored to the IGN terminal and buzzing with key on has stopped. Not sure when this fuse may have blown though, because the turn signals were still working as of earlier in the day yesterday and had been even before I replaced the ignition switch.

Also not sure if or why a blown t/signal fuse would cut the IGN voltage level to such degree that the car would shut down mid-motion (I'm running a wire directly from IGN to my HEI coil). Starting to sense there may be a new dash harness in my future.

oldcutlass

The IGN terminal gets its power from the turn signal fuse. Make sure your not overloading the circuit with anything else besides the HEI.

70sgeek

that wouldn't have occurred to me since the IGN terminal was still reading voltage up to the point I discovered the blown t/signal fuse.

Only other thing I can think of is I have performance bulbs in the turn signal housings which maybe drawing more amperage than stock, but they've been in use for well over a year.

Wondering now if not something developing in the t/signal switch...

oldcutlass

What could have happened is the clips that hold the fuse were getting corroded and the fuse was starting to lose some contact increasing the load causing it to blow.

matt69olds

cjsdad

Make sure your battery-to-block and head-to-firewall grounding cables are clean and tight. If the ground is weak the electricity will find a way to feed back through other circuits and blow fuses.

oldcutlass

Except in this case the ground is connected to the engine block and the distributor gets its ground through the engine block. This is not a ground issue. When your missing the ground strap it finds ground through various other places, cables, trans linkage, body mount bolts, etc...

cjsdad

If the ground between the engine and the body becomes compromised the electrical circuits including the ignition will find a new way to complete. That will also include smaller circuits that are and are not being used at the time. Like the lighting circuit! Remember the first rule of electricity, it will find the path of least resistance, even if that path is already being used. I have seen poor stereo installations melt the fuse box feed because of bad grounding. It happens!

70sgeek

I'm hopefully good in the grounding department - my battery cables are new (M&H) and I'm grounded to points on the frame, block and firewall. I took a small wire wheel to the t/signal fuse connectors and the new fuse seems to be fine - had the car out a few times this week and all thus far good again. Have been pulling my coil power from the IGN terminal on fuse box for full 12v.

My dash wiring is original, clean and uncut but may be in need of replacement simply from age - I recently came upon a good OPGI sale and am saving $100 off the price of a new M&H harness, no tax + free ship. So that will be my next major project.

Interesting you mention stereos - the new Custom Auto Sound unit I installed a few months back essentially won't operate properly due to what they allege to be high EMI feeding back through the electrical system with the engine running. I've been unable to isolate the problem no matter how I tried grounding the unit, insulating and/or re-routing wires... The power output just keeps randomly dropping down as if it were cycling through a protection mode. CAS said they can't test it because they don't have equipment to duplicate an engine-on condition.

The radio was disconnected at the time the car shut down so I know it had nothing to do with causing it.

To me, electrical gremlins are the worst part of maintaining a classic car - I'm very appreciative of the great info everyone on this site contributes to help keep these cars going

cjsdad

I was talking about a stereo with a poorly installed amplifier that draws a much higher amperage than the factory electrical system can handle. I have seen people tie the main supply lead of the amplifier into the fuse box of a vehicle and because of the high demands of the amp, burn out the factory wiring system. I have also seen amps installed properly but the vehicle ground missing due to an engine replacement that would starve the vehicle of electricity, again because of the high demands of the amp. Burned out fuses because the amp was finding ground potential through unused circuits.

Are you using an amp with your stereo? Not related to your electrical problem, but the shutdown issue. Are you getting "engine noise" through the system? It is quite possible a shorted speaker wire would cause the symptoms you are describing.

70sgeek

No amp, just the radio and 2 Alpine 6.5" kick panel speakers - all new components and good gauge speaker wiring installed. I've seen my share of cringe-worthy installs as well over the years - once had to rebuild practically an entire '76 corvette dash because of a prior owner stereo hack job.

Not getting any feedback noise at all - only the power fluctuation causing volume drop each time it cycles. No change in the actual volume setting, no display fluctuations, actual full power loss, etc. I've tried adding ferrite magnets to the wires, insulating them in copper audio tape, re-routing them as far away from other wires as possible, multiple grounding points, etc. Can't fix the issue. With key-on engine off, radio plays flawlessly.

cjsdad

Only thing I have left for the stereo is bad vehicle grounding or alternator/regulator when running. Glad you were able to get it running!

70sgeek

All else seems to be in good working order - I run an Auto Meter volt gauge which shows 14v+ measured from the IGN terminal when engine on - also metered the voltage at alternator (a Powermaster internal regulator unit) and it's a constant 14.5 or so running. No headlight dimming issues even with brights on, no dash lamp blinking with brakes, etc. Will be plugging another radio into the car for testing at some point soon and see how that goes.