QuadraBog - No - Patience is a virtue

[jeffahart]

Thought I would post a problem I just encountered to illustrate a few things.

Symptoms: Vehicle bogs out on acceleration on secondaries. But only with the air cleaner ON.

Hmmm. I had recently installed a hyroboost and took out the vacuum boost, keep that in mind.

So, there I am scratching my head. Made a few phone calls that night and got the usual toss the Qjet, plus some: up the advance, check the coil, don't get rid of the qjet... and so on.

So, I test the coil and spark: I got heat and fire. No problems there, checked the plugs, looked good. Reset the timing by feel. My engine purrrrs like a top.

I checked the connections for loose and just could not get anything foul in the garage. I was really looking at that carb wishing I had another one on the bench so I could test it.

Made no sense, runs like a top, and awesome WOT with air cleaner OFF.

Now, had I posted this issue, I'm sure with ignition being ruled out, that we would be divided... Toss the Qjet.. keep the Qjet and tune it.

But since I'm a Qjet lover, I was hard pressed to blame my beloved Qjet. Plus I never had such a bizzare behavior. I started looking at my beloved skip white $19.95 distributor. Bit It also kept bugging me that I unhooked a major player in vacuum consumption and then I get this problem. I don't like a coincidence, something doesn't work right after I changed something. Always looking at the last thing I did.

After thinking about it I took action.

I grabbed a 3/8" piece of doweling from my doweling stock and started the engine. I started spanking the plug wires, distributor and coil wires to simulate road vibration.

Then I saw it, a slight spark. At first I kind of ignored it, thought it was glare. But then I got it again, and good. The power wire to the coil. Ha! The power wire got poorly routed and got rubbed raw in a small spot by the throttle linkage. You know how it is, so small is the worn area you can hardly see it.

So what was happening was the Air cleaner was pushing the wire close to the linkage. When the linkage got close the the wire, right about where the secondaries would kick in, bang short and power cut at the critical point that exactly mimicked a serious bog hesitation.... let off the throttle and power up. Almost like the secondaries were opening too soon.

A rookie type mistake of not paying attention to where wires are routed, by just being in a hurry or careless.

So.. what if I had not seen that spark. I could have put on a new carb and maybe even a new shiny air cleaner that did not push the wire into the same position, and I would have thought I solved the problem by ditching my beloved QJet.

But since I know a bit about carbs the symptoms really did not add up. So I kept at it.

Patience is a virtue when it comes to chasing problems. Whether you love or hate what you have, be it the carb or distributor or whatever, you need to give it a chance. Knee jerk blame is easy.

I love my Qjet, but I was blaming it for the issue and almost pulled it for rebuild and tune.

[huntznsam]

Thank you for the great reminder. Patient diagnosis beats part swapping! Finding that short was something to be proud of.
Huntz

[geunther]

Important story. There is always a culprit, always. Good job from another QJet liker.

[dmjlambert]

That is great troubleshooting and lesson, thanks for sharing that.

[special-K]

Good example of another case of it's not a common problem anyone can think of it being. Saying toss the carb that sat on top of the most commonly used engines ever, that gave far less problems than their competition, are not the words of a true mechanic.

[Ken B]

Originally Posted by special-K

Good example of another case of it's not a common problem anyone can think of it being. Saying toss the carb that sat on top of the most commonly used engines ever, that gave far less problems than their competition, are not the words of a true mechanic.

Amen to that! For every day use on a daily driver you simply can't beat a properly tuned Qjet!

[52napco]

Kudos for not just throwing a piece of crap edelbrock on your truck.The quadrajet is a
great carb.

[cleszkie]

I'll bet you considered, at least for a second or two, just tossing the air cleaner out and driving the wheels of it Glad to see another fine example of how simple things can be mistaken for more serious problems.

[jeffahart]

Originally Posted by cleszkie

I'll bet you considered, at least for a second or two, just tossing the air cleaner out and driving the wheels of it Glad to see another fine example of how simple things can be mistaken for more serious problems.

Ha Ha ya for sure. I did try sticking in a taller filter I had. Stupid little issue really exercised me... and I hate exercise!!!

And just for the record, what I wrote up above is the short version! I just didn't want to bore everyone with all the hoop jumping details and everything I tried.

But I kept coming back to vacuum, I had removed the vacuum boost and no secondaries when I punch it, and with filter on only. Made no sense at all. Really a pisser!

And what would have been worse is, if I would have moved the wire, by just fooling around and the issue would have stopped. Then I would have been haunted for months thinking about how the carb needed a rebuild. Too funny!

[demian5]

Originally Posted by jeffahart

The power wire got poorly routed and got rubbed raw in a small spot by the throttle linkage. You know how it is, so small is the worn area you can hardly see it.

I had the same type of issue but only when driving at night. Caused it to cut out.

The linkage on my dual carbs (VW Bug) would hit the tail light connector in such a way that it went into the connector where the wire was - but ONLY under hard acceleration at night.
Both had to happen at the same time:
1. Harness had to move backward in the vehicle under Gs (front-to-rear direction)
2. Linkage moving to the full throttle position (up-to-down position).

Battled this for a while. Then one night I had the decklid off cruising with friends (gotta show that motor off) and my friend behind me says "hey, there is a spark from your carb linkage."

Goofy problem located and solved.

[MagmaJct]

Originally Posted by demian5

I had the same type of issue but only when driving at night. Caused it to cut out.

The linkage on my dual carbs (VW Bug) would hit the tail light connector in such a way that it went into the connector where the wire was - but ONLY under hard acceleration at night.
Both had to happen at the same time:
1. Harness had to move backward in the vehicle under Gs (front-to-rear direction)
2. Linkage moving to the full throttle position (up-to-down position).

Battled this for a while. Then one night I had the decklid off cruising with friends (gotta show that motor off) and my friend behind me says "hey, there is a spark from your carb linkage."

Goofy problem located and solved.

Getting slightly off topic, but being a VW owner and fan myself, your story reminded me of mine. For a few years, my turn signal would randomly blow a fuse. Maybe 3x a year. I eventually ran out of 8 amp fuses, so I popped the next size up in the slot. 16 amps! I figured if it was a real short, the fuse would still blow.

One night on the highway I used my signal and my headlight started blinking! So bizarre! When I got home I tried to reproduce the problem. Not only could I not reproduce it, but the signal wouldn't work and the switch no longer had its detents.

Turns out I had burned out my turn signal switch. The cause? There's a floating terminal junction in the trunk that's insulated with a plastic sleeve. The plastic sleeve had shifted exposing the crimped end of a wire terminal. Depending on the position of the junk in the trunk, the wire might be pressed against the steel and make a low resistance short. Somewhere between 8 and 16 amps!

Lesson learned. Don't use a higher rated fuse than what every component in the circuit is designed to handle!

[Coley]

Great story and some excellent troubleshooting work there.
I can't count the amount of times that I've witnessed or heard about guys throw out good stuff and buying new stuff in its place in hopes of solving a problem without really knowing what the problem was to begin with.
Carbs, fuel pumps, coils, distributors, alternators, heads, valve jobs, engines, transmissions...you name it....the list and the money spent is 5 miles long.
Its always worth it to figure it out and its always way more interesting. However it takes those great attributes....(wait for it)....patience and ability!...lol......often in short supply when it comes to guys working on stuff.


By the same convention I will not let any repair facility proceed with any work on our (newer) vehicles without telling me specifically what the problem is.
....show me the exact point of failure...or no deal....this 're and re' stuff (remove and replace) until the vehicle starts to apparently run better doesn't work for me.

Great to hear you solved it tho' without dumping money.

All good
Coley

[bill3rail]

I remember chasing carburetor problems in a van decades ago and the wires were bad! More than enough to piss you off when you figure the issue out.

Glad you stuck with it, and thanks for sharing it here.

[Steeveedee]

Good job on the diagnosis. Nothing worse than just throwing parts at a problem until it goes away. I was a mechanic back in the day, before I graduated university and went to work as an engineer. People would come into the shop all the time with complaints about the carburetor. The first time, I just put the carburetor on because the customer said that was the problem. It wasn't the problem, and while we still got paid for the carburetor and labor, I felt bad about it, because it wasn't fixed, and there was added expense to make the correct repair. Funny that I remember about the carb, but don't remember what the real problem ended up being! After that, I always did the diagnostics. 95% of the time it was in the ignition, when they had points.

My truck had a secondary bog that took some time to figure out- the plastic cam that raises the secondary metering rods when the secondary air valves open broke. But I knew that it was in the carb for sure. The only kit I've ever seen with that part is one I bought from Cliff Ruggles.