1968 Need help from the engine gurus.....

[azbeneman]

Guys & Gals,

I am at the end of my rope. I completely restored my GTCS 12 months ago. I have about 1500 miles on it. It is a stock C Code/auto with about 40k on the rebuild. New battery and alternation durning restoration. I run the Petronix Ignitor and Petronix coil. I have a mini tach and aftermarket air installed as well. The carb has been restored and the entire package ran great until about a month ago.

The car completely dies when making a left hand turn from a stop. Not every time, but about 25% of the time. It also dies at freeway speed and will completely shut down while cruising at 60/70 mph.

Here is my timeline for the past month:
Instrument cluster resistor died, took out cluster and replaced it. The engine problems where intermittent at this time.

I thought it might be a fuel issue, so I replaced both the fuel pump and filter (the tank and lines are 1 year old.). No change in the way it ran.

Around this time it complete shut down at 70 mph on a left turn freeway interchanged. No where to pull off, traffic coming up fast, I panicked - put it in neutral as it coasted down and restarted it. 3 huge backfires came immediately resulting in blowing out both mufflers. I guess the fuel pump is working good! No apparent damage to the motor, no leaks anywhere.

I was told by a local shop that it could be the ignition switch so I replaced it. I was also told the resistor wire (pink wire) going from the ignition to the firewall can some time mess with the Petronix. I cut it and wired in a straight wire in its place. No change in the way it ran, if anything the engine shutting down became more frequent.

I focused then on the Petronix. Borrowed another one from a local shop, installed it and the car ran worse. Put my Petronix back in. Runs better but sill dies.

The rotor looked a bit worn so I replaced it. No change.

Focus my attention to the coil. Removed the Petronix coil and installed the std one that came with the car when I bought it. It ran the same, but still died on straight aways around 35 mph. I reinstalled the Petroix.

Maybe the Mini Tach is the problem. I disconnected it(and wrapped the end with electrical tape). It died about a mile from my house. Got it restarted, it felt better so I hopped on the freeway. After about 5 miles it shut down at 65 mph, back fired twice as I coasted to a stop. I limped home on side streets.

So I am at a loss. Any suggestions are appreciated.

Craig

 

[Mosesatm]

Something sort of similar happened to me years ago. I found out that the back of the ignition switch was loose and once in a while it would lose it's connection to the main part of the switch. The car would die, I'd pull over, turn off the key, turn it back on and the car would run fine until the back of the switch jiggled loose again.

You may have a loose electrical connection there or somewhere else, you may also have a bare wire touching the body or frame. At high speed the rushing air may be moving a wire back against the firewall and shorting it out, or the air may be pulling the wire partly out of a connector.

 

[p51]

Well, it sounds like you're on the right track with it being an electrical/ignition related issue. The stall on left-hand turns seems suspicious - is there anything electrical in the steering column that is any way related to ignition? Could something in the steering column be causing a dead short of 12V to ground? Would it make sense to temporarily wire up a separate ignition circuit (a hotwire of sorts) to see if that removes the problem?

This might be of some marginal help...
When I was a kid my father's Toyota pickup had a similar problem. You'd be driving along fine, hit a rough patch on the road, car would sputter, backfire, shake (sometimes die) and then start to run perfectly again. Turned out the bracket that held down the battery had come loose and it would bounce around sometimes hitting the positive terminal shorting it to ground intermittently causing a major power lose leading the ignition to misfire. The shaking would then bounce the bracket away from the positive terminal, get a really big backfire from all the fuel in the muffler (one of which actually split the muffler), and then everything would be fine... until you hit the next bump in the road.

 

[Ruppstang]

I recently had a bad solenoid that would cause loss of ignition when revving.
When we checked with a volt meter we found only 1.5V, Tapped on the solenoid and got 9.5. It may be something else to check.
Marty

 

[green56]

car shakes in idle

hi everybody having trouble with car shaking in the idle put a different carb and still does the same thing when you step on gas runs good but not at idle timing good it has 48 jets put in a brass floot when you step on gas and listen to engine at the exhaust and it sounds like it is missing have new plugs and wires compression goes from 155to165 drilled out jets to 52 still the same any help ?Now we think it could be the roll rockers could that be???? I would hate that i would have to pull the engine and go thru it once is enough Thanks Tom WI

 

[BigJim]

Had a car back in he late 70's that would die if you coasted around a left turn. Give it a little gas during a left and it kept on running fine. It would coast around right turns all day without a hiccup. It was a carb issue that went away with a carb clean and rebuild.

 

[rvrtrash]

The first thing I would do is pull out the Pertronix and put standard points in, just to eliminate that as a possibility. Since you've cut the resistor wire to the coil, if you use a standard coil, you'll need to install a ballast resistor. The carb backfiring leads me to think of a fuel problem. I don't know what carb you're using, but if it's a side pivot float, and it's not adjusted right or is sinking, that might be causing a flooding issue that get's worse when turning. Rob can chime in here. And because I'm more in tune with the electrical side, I would also check the connectors you've installed on the wires to the coil, and connections in between and all grounds. Crimp connectors can develop broken wires at the connection, not be crimped correctly, or develop corrosion-which translates into increased resistance.

Steve

 

[66hcs-conv]

I don't know for sure about the 67/68's, but on our '66, there is a big negative cable that runs from the battery negative down to the passenger side of the engine. I had a radiator leak that had corroded that connection at the block, and was causing different weird electrical stuff.

I took the bolt out, shined everything up, and used several external/internal lock washers, sandwiched between the different cables and the auto trans line clamp, to make sure everything was making contact.

Hope this helps, Dave

 

[Mosesatm]

What Steve and Jim said.:thumb:

The problem may be that the float is stuck or it's set too low. Low fuel in the bowl would kill the car during a turn, and it would run the bowl dry during high speed cruising.

 

[azbeneman]

Thanks for the suggestions. The battery cable is snug. I took the car in to put it on a diagnostic machine. The timing was advanced 18 degrees. It appears the triangle holding the distributor in place was not tight and it may have been bumped forward. Engine on, the battery was at 14.3 volts, the coil was 11.5 volts with the Petronix set up. We backed the timing back down to 10 degrees.

The other thing I found is that at about 2700 rpm, the PCV hose collapsed on itself. It is an older hose, so I replaced it.

I drove it home on city streets and it ran fine. I hooked the mini tach back up. I noticed this am that there was a slight lumpiness at idol. I thought one of the spark plugs could have gotten damaged in the backfires. I replaced them. Looking at them, they seemed fine, but the gap on 3 of them was less than when I put them in a year ago. I still could feel the lumpiness.

I drove it 5 miles on the freeway and it shut down again. Not all the way, the engine caught itself and fired up. On the way home, I pulled off at my exit and it died completely.

Next up, pull the carb to inspect it (Std 2100 that was restored last year). I need to try another starter solenoid, but need to buy/borrow one. My original is gone.

What are the symptoms of a timing chain that is about to go?

Craig

 

[robert campbell]

Craig,
First thing and real easy is to run a wire from the positive side of the coil straight to the positive side of the battery. This will provide a constant 12 volt source to your coil/distributor. Do not worry if you have the points back in or not for this test. A point system likes 7 to 8 volts to keep from burning them. A Pertronix prefers 12 volts.

This will eliminate almost all of the possible switch, solenoid, and tach possibilities. If this eliminates the problem it is the ignition switch or power to from the switch to the coil.

If the problem persists, then it is another issue such as the module or possibly the carb. Of note, to turn the car off you will need to get out and remove the power wire from the battery.

Rob

 

[Ruppstang]

Rob I like the way you are thinking. I am with you.

 

[robert campbell]

To owners of Mustangs. The check above is also how easy it is to steal your car. A thief with a short wire and two alligator clips can provide 12 volts to your coil. Then using a small screw driver he/she can short between your solenoid post and the battery terminal to roll your engine. It will start and run.

He/she can only drive as far as your battery will hold, but even in the dark they can drive 20 miles or so.... In daylight without head lights and other stuff they can drive a long long ways!

My car has a hood lock to eliminate this. And the club is the next best thing. Car alarms are basically useless. No one listens to them anymore.

Fortunately the common thief is just looking for a Honda Civic....

Rob

 

[p51]

What are the symptoms of a timing chain that is about to go?

Craig

Here are a couple of videos on how to check timing chains...

https://www.youtube.com/watch?v=4_f5ukZVri8

And on a SBF engine...
https://www.youtube.com/watch?v=bWP1qsi7Hjk

 

[robert campbell]

A timing chain will not cause your symptoms. But checking it is a good thing. Very easy to do.

Rob

 

[GreenSpark]

To owners of Mustangs. The check above is also how easy it is to steal your car. A thief with a short wire and two alligator clips can provide 12 volts to your coil. Then using a small screw driver he/she can short between your solenoid post and the battery terminal to roll your engine. It will start and run.

He/she can only drive as far as your battery will hold, but even in the dark they can drive 20 miles or so.... In daylight without head lights and other stuff they can drive a long long ways!

My car has a hood lock to eliminate this. And the club is the next best thing. Car alarms are basically useless. No one listens to them anymore.

Fortunately the common thief is just looking for a Honda Civic....

Rob

When it was my daily driver, I used to pop the hood and fiddle around with the engine after parking, pocketing the coil wire in the process. Thieves rarely carry a spare coil wire.

 

[Mosesatm]

If I were a thief I'd use one of the spark plug wires if the coil wire was missing.

I always used a dummy coil wire.

 

[68 special]

I found a shifter with a key lock. They might get it started, but getting it in gear will be challenging. My hope is they can't figure it out and trying to remove the handle is pretty much impossible to do quickly.

Note to self, get a spare key made!!
Bret

 

[robert campbell]

Hey Craig! Where are we these days??

Rob

 

[azbeneman]

So the car show I was getting ready for, The Run to the Pines in Pinetop AZ was last weekend. The GTCS stayed home, bit I went anyway. The funny thing is, of the 4 guys I go with, only one car made it this year.

My Grandfather is in town so we worked on it this afternoon. He is pretty handy with old cars. He definitely thinks it's electrical. Now the car is dying every time it gets up to highway cruising speeds. No longer dying on left hand turns though.

We chased the wires under the hood and found the brown wire on the starter solenoid was barely attached. We tightened that connection, but it is still not running right. He didn't like the fit and shape of the rotor. We put the old one back in. Before and after, the idle is not real smooth. Driving around town seems fine though. He thinks I should get a different cap because the one that is on there doesn't seem to fit real snug. After that, we are going back to points. I haven't done that yet because I need to buy a screw that secures the points to the distributor.

Another thing, I need to check my receipts, but I am pretty sure I bought a new alternator wiring harness and alternator when I rebuild the car. I can't find where the resistor on the alternator plugs in with this new wiring harness.

I am beginning to think my distributor is off by one tooth. How do I know when the distributor needs to be rebuilt?

Craig