The Stovebolt Site Forums The Shop Area Engine Shop Ol' Roy Blew a Stinker / Busted a Grumpy / Cut the Cheese on the Drive Home

Ol' Roy has been sitting more or less idle since the end of June. It was out at my mom's house because I needed his usual spot temporarily for another vehicle.

Anyway, it started and drove normally - nice and smooth with no fuss.

I drove about 15 miles to top off 18 gallon tank at Sam's Club before getting on the freeway. It only took about 6 gallons of87 deathanol - the fuel which Ol' Roy has been using nearly exclusively for the last 4000+ miles.

I got on the highway and accelerated up to cruising speed of ~55mph. So far, nothing out of the ordinary.

About 5 miles down the road after crossing the Chattahootchee River, the highway starts a long, but not steep, incline.

At some point the truck seemed to be losing power almost like you'd experience with a slipping clutch or if the engine was starving for fuel. In the split seconds while my brain was trying to figure out what exactly was happening, I let off the accelerator and there was a sudden LOUD CRACK! which I felt through the floorboard.

I thought the transmission exploded but quickly determined that wasn't the case. I looked in the rearview mirror and saw through the beams of light from the cars behind me (who were themselves, slowing down and backing off) a cloud of smoke.

This was at night so I couldn't tell you what color the cloud was but I figure it was black. After my brain caught up with events, I determined/assumed that the truck had backfired and likely shot a flame out the tailpipe, which scared the people behind me enough for them to put some distance between themselves and my bumper.

After that the truck showed no other problems. Several more hills - steeper that the last one - had no effect on the engine at all. It didn't lose power, didn't stutter, didn't backfire, or anything.

When traffic got heavy on the downtown connector and I had to slow down to 10-20mph, the engine ran just as smooth as ever.

This morning I checked over the truck thoroughly. No hole in the muffler, no water in the oil, oil full, radiator full, no visible debris in glass fuel filter bowl. Truck started right away and idled smoothly with no smoke from the tailpipe or anything else out of the ordinary.

I suspect maybe water/debris in the fuel I had just put in the tank but who knows?

Do any of you have any ideas of what likely happened? As I drive the truck from this point forward I'll soon learn if that was a fluke or of there is some endemic problem.

Just FYI, tank and lines are new. Pump and carb are newly rebuilt with over 4000 miles on the carb and probably 3000 or more on the pump. Points were replaced a couple weeks ago.

Maybe carburetor icing. A rare thing , but I’ve had it happen. High humidity and just the right temperature.
The frosty ice just melts away afterward.

It sounds like you had a momentary ignition failure - - - -maybe an open or short in the wire between the coil and the distributor, or a wire inside the distributor getting shorted for a short time. It's the equivalent of turning off the ignition switch for a short time, allowing unburned fuel to accumulate in the exhaust, and then turning the switch back on. The boom and flame out of the tailpipe can be very impressive!

Try jiggling the wire between the coil and the side terminal of the distributor to see if you can make the engine stall. Since the vacuum advance keeps that connection in constant motion, it's not uncommon for the strands of wire to get fatigued and develop an intermittent open circuit. I like to use a piece of high-flex wire that's normally used for test equipment leads in that application.
Jerry

Temperature was in the high 40s. Humidity is/was in the 33% range so it seems unlikely.

I drove the truck last year in 12 degree weather on the same route without trouble.

I did experience carburetor icing in 2002 with The Bismarck. It was a fluke weather pattern where a blanket of heavy fog covered Atlanta at night

during temperatures in the 30s. Car conked out and on my inspection found ice all over the outside of the carburetor base and inside the venturi.

I will second what Jerry said. As a teenager, that was my favorite prank. Drive my car past a friends house after dinner time, get some speed up, cut the ignition switch off, coast a little then turn the switch back on. Boom, like an old school m-80. Very impressive indeed, until I had to pony up for a new muffler that is. Fast forward 25 years, my 1948 GMC had an intermittent ignition switch that did that if it got bumped or vibrated. As an adult, I changed that out right away.

I will check that connection.
aS YOU ALL MAY RECALL, i RECENTLY HAD A burned points problem and during my search for the problem I removed and cleaned all the electrical connections on the coil, battery, etc. I'll go look at them again and try the jiggle test.

I keep an assortment of sizes of that flexible wire on hand. Any circuit that's subject to movement or vibration gets wired with it, and the terminals get soldered- - - -not crimped. I learned that little trick about 60 years ago when Ford distributors had a nasty habit of breaking primary wire strands between the housing grommet and the points. We would diagnose the problem by disconnecting the vacuum advance. If the stutter on acceleration went away as the wires quit moving, that piece of primary wire got replaced. Apparently, Furd got a bad batch of wire at the factory, and a few million cars got equipped with it.

The scary part is that people like that parts department computer jockey reproduce!
Jerry

I just went out did the jiggle test on all the wires I could lay my hands on. Nothing seemed loose and no amount of wiggling, pulling, pushing or otherwise resulted in an ignition cutout or discernible change in engine behavior.

I even went in the cab and monkeyed with the ignition key to see if it was loose or if any amount of wiggling would cut it off but that didn't result in a cutout either.

I don't like the looks of the wires to the coil anyway so I think I will replace them both. The positive one has one of those K Mart connectors where it ties into the main harness.

Those type of connectors were used by the prior owner to mess up the headlight wiring.

Did you happen to look under the distributor cap for worn insulation on any internal wiring? Since the breaker plate doesn't move on a stovebolt distributor, it's not a common problem, but a pinched or mis-routed condenser wire can get grounded out intermittently and cause problems. The insulator that goes through the distributor housing can also be a source of random ignition problems.
Jerry

While you have the distributor cap off, you should look to see if there is a crack in the cap. I've had back fires from a cracked distributor cap.

I will look at those things now. I just got back from a test run where I tried to induce the stall or backfire but I couldn't make it happen.

The condenser is a J Goodman Special and I just had the cap off a couple weeks ago checking everything with a microscope when I changed the points. All looked good then but I'll look closer now.

The 15 miles before it started acting funny….was that highway driving or lower speed kind of stuff?

Was just thinking maybe you had a partial exhaust restriction (mouse house) that didn’t rob power until it moved a bit. Caused a significant restriction for a few seconds, and then lit off. 6 months of sitting is enough for Fievel to make a home.

The ignition explanation is probably a better one.

Well, around here, speeds on local roads and highways are about the same, especially in a truck with a top speed in the 50s.

The 15 mi drive was 45-50. The highway was 50-55.

My mom has two cats which keep critters under control so I'd be surprised if that were the case but it isn't outside the realm of possibility.

Testing my memory.

A long time ago, Dad had a more modern (454) engine that would very occasionally let loose with a backfire that sounded like a cannon.

Culprit turned out to be a graphite gap in a factory radio suppression spark plug wire. Guess how long it took to find that!

If the load was just right and the ignition advance was at a certain point, KA-POW!

Not saying this is your problem, but my vote, like others in this thread, is ignition.

Will be interested to learn the solution.

Jon

I agree that that's the likely problem. I inspected the cap and rotor for graphite, dirt, whatever yesterday but no problems are evident. I took it for a drive and tried to induce the problem to no avail. While driving at various speeds and loads I played with the keys in the ignition but there is no looseness at all. I'll check the wiring to the switch when I feel like performing some Cirque du Soleil maneuvers.

I'll keep looking and if it happens again I'll know for certain it wasn't a fluke.

Yeh, i would not count on that. Most cats that a fed well will not help control rodents. My friend just had his truck burn up
because of squirrels making a pine straw nest on his engine while parked for hunting.

I was just thinking maybe the second leg of the journey was a higher speed/higher load condition that made the obstruction more noticeable. But it could just as easily be that the nest moved around enough with exhaust pressure to create a more significant plug up, which promptly cleared itself.

But overall, I think the ignition explanation is more about plausible.

Interesting clues:

1) felt the power draw down for a few seconds
2) it backfired once you let off the throttle

Jerry’s explanation of the coil-to-distributor wire doing something funky fits # 2 pretty well. Dizzy would have been rotating as you let off throttle. But I’m struggling to understand the draw down in power preceding the backfire with that one. Shouldn’t a problem there have created a more complete (even if just momentary) loss of ignition?

Something funky in the centrifugal or vac advance is possible. Weights hang up and don’t advance = retarded timing…this explaining the poor power. Backfire occurs once timing comes back to a natural “happy spot” as the RPM came down when you let off. Then again, I can’t imagine why that would happen once, self correct, and never happen again.

Carbking’s story is a good one. Similar….super-flaky, ignition issue that is dependent on multiple factors coming together.

Stovebolt wiring is caveman-simple. Try diagnosing 100+ miles of wiring in a B-52 sometimes- - - - -particularly if your "shop" is located at 20K feet above sea level and Hanoi Jane is shooting at you, on the way to deliver 15 tons of high explosives- - - - -on time and on target!
Jerry

I drove it for work today with no problems. This weekend I plan to go over the wiring from switch to coil and everything related to it.

Well you guys, it happened again a few hours ago under nearly identical circumstances so we now know for certain that Tuesday's incident wasn't a fluke.

Headed out this morning to run errands. After about a 5 mile run on the interstate (no secondary road cruising leading to the highway) I began losing power after on a long but not steep incline. I let off the gas, took it out of gear to downshift and got the big Ka-Boom!

My exit was right there so I exited and experienced no more trouble on the secondary roads (30mph max).

On the way home I took secondary roads (30-45) with many steep hills, some fairly long. Absolutely no problems on the rest of my errand running which totaled probably 15 miles.

The only new part in the ignition system is a set of points installed a few weeks back. Could points be floating? I've never experienced that in my life despite driving breaker point ignition vehicles almost exclusively.

Does point floating manifest itself intermittently or would it be all the time?

During both incidents the headlights were on. I don't think that's relevant but who knows? Heater was on during the first one and turned off during today's event.

Try running a temporary ignition switch circuit- - - -a toggle switch that bypasses the ignition switch and wiring, straight from the battery cable at the starter- - -into the cab- - - -and back out to the coil + terminal. That will eliminate any potential primary wiring problems and focus attention on the coil and distributor wiring. That cuts your diagnosis area at least in half.
Jerry

Thanks, Jerry.

I happen to have a new toggle switch in the garage and some 12ga wiring left over from the headlight repair last year.

Would I need to disconnect the ignition switch, too or just leave it there turned off?

It doesn't take anything funky inside the distributor for that kind of thing to happen. Back when I was a kid driving a Model A, a favorite trick was turning the ignition off momentarily and back on to produce a pop out of the exhaust. Depowering the coil at a random point will fire a spark plug when it's not supposed to be (like when an exhaust valve is open). I'm with Jerry that the issue is with either the ignition switch or the wiring to the coil.

Sounds logical. I'm not happy with that wiring, either.

It shows evidence of having been repaired by the same dyslexic nitwit who mixed up #3 and #4 plug wires, mixed up the high beam headlight wire and the main headlight hot wire, and transposed two characters in the serial number when he titled the truck.

I'll either run a temporary switch as Jerry suggests or replace the existing wiring - which has been on my list to do anyway.

Might worth running a temporary wire/switch to verify that it fixes the issue before making a larger change that could introduce other issues.

If you put Jerry's switch in and leave the existing switch in place, the next time it acts up turn the temp switch on and see if the problem goes away...

I also agree with Fibonachu, find the problem before you tear everything apart, so you know you actually fixed it...

Mike B

Yes, that's what I always do. I hate just replacing parts on spec. I will closely inspect the existing wiring as I planned to do anyway and maybe find the problem.

Your idea of installing the bypass and leaving it turned off until the problem starts is a good one.

Sounds like this is related to the "no spark" episode back in your mom's garage. The starter conked out so the intermittant loss of spark issue? Those "come and go ghosts" can really drive one crazy.

This situation reminds me of a gremlin we chased on a B-52 years ago. One of the systems my shop maintained was the autopilot. Three electric motors in the system moved the manual controls, which were simply cables and bellcranks attached to the pilot's column and rudder pedals. One plane had a chronic stiffness in the controls which only happened at altitude. Back on the ground, or at low level, the problem went away. After weeks of swapping parts, one of the maintenence guys I supervised found a piece of wet rag wound up in an aileron cable sheave. At high altitude and below-zero temperatures, it would freeze and restrict the control surface movement. By the time we got the (repeated) work order complaint, it had thawed out, and the problem disappeared.
Jerry

The real investigation should have then been to discover which of the Techs. left the rag in there in the first place.

Well, Gents, I hooked up my hotwire switch and took a test drive. (toggle switch running to battery post on starter and to positive stud on coil)

I still lost power and backfired. It seems to occur when approaching "top speed". This happened when I was running with the key off and my new hotwire setup only.

On the way back from by trip to the next freeway exit I attempted to push the truck faster and immediately experienced the loss of power "bog". When I let off the gas, the truck sort of smoothed out but did backfire as I was moving up an inclined exit ramp.

The primary wiring and switch does not seem to be responsible for the backfire, correct? That leaves coil, dizzy, points, cap, rotor, wires and plugs, right? That's if the problem is indeed, electrical.

I should mention that I removed the points yesterday to study them and reinstalled them gapped at .022. I checked all the plugs again today and they're clean and properly gapped.

The coil is "new" a couple of years ago. Are the new coils as well made as the new fuel pumps and condensers?

Just to refresh people's memories, the truck ran fine in June on a 40 mile run. It sat until a few weeks ago when I discovered the burned points and dead starter. It was driven about 35 miles total on several occasions when I was out there visiting my mom. No problems manifested themselves during those drives on local 30-40mph roads.

I don’t recall all the burned points backstory stuff. Was ignition key left on for an extended period or just an unknown cause?

That was from this thread. https://www.stovebolt.com/ubbthread...o-spark-then-no-starter.html#Post1521739

Page six has a picture of the points.

I cannot categorically state that the key was not left on. It was stored in the house away from the truck while the truck was parked.

It isn't outside the realm of possibility that it was left on during attempts to start the truck but I don't think so.

Points installed in it now are AC Delco, not that that makes a hill of beans difference. Brand names mean nothing these days.

I have ordered a couple new Wells sets.

.022 seems a little wide to me... I've set my points to .019 for 60 years. .003 may or may not make that much difference. What does your dwell meter read?

.022 is what the shop manual says to set new points. Gap is .018-.022. They say .022 to allow for wear on the rubbing block which will bring it down to .018.

This morning and just a few minutes ago, I started the truck and it bogs immediately upon pressing the throttle and pops through the carburetor.

Doers this still sound like ignition?

The truck did this with the old wrong carburetor before I got a correct one from Jon and rebuilt it.

At Idler I just looked down the throat of the carb and saw a lot of gas piddling out in the center. Seems like needle is open or over filling bowl or something.

It sounds to me more like a fuel problem than an ignition problem. When for some reason there is excess fuel being delivered the engine bogs down and as that raw fuel finds its way into the hot exhaust you get a backfire.

I think it’s probably time to backup and revisit some basics.

Does it idle well and long enough to stick a vacuum gauge on it and get a reading?

Remind me – have you done anything to check timing since all this began?