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Engine stumbling badly off idle
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Clatter
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PostPosted: Mon Jun 07, 2021 11:05 pm    Post subject: Re: Engine stumbling badly off idle Reply with quote

Maybe put the hot ignition back in?

You didn’t leave the plugs gapped big by any chance..?
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Slow 1200
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PostPosted: Tue Jun 08, 2021 12:20 am    Post subject: Re: Engine stumbling badly off idle Reply with quote

Quote:
So where did I lose you?


67rustavenger wrote:
The engine starts with difficulty and once running. I cannot get past the idle circuit without it acting like it's starving for fuel.
It runs so poorly that it will not idle long enough the set the timing.


Quote:

If I manage to get past the idle circuit, the engine responds fairly well. But once back on the idle circuit it's hard to get up in the revs again.


Quote:

Once I rolled into the carb transition from idle circuit to the mains.
The engine responded like there was either no fuel, or the ignition had stopped working.
When I backed off the throttle pedal, back into the idle circuit. The engine came back to life. But it still would not rev beyond the idle circuit.


well...for one it looks like there has been a variety of symptoms
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Alstrup
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PostPosted: Tue Jun 08, 2021 4:11 am    Post subject: Re: Engine stumbling badly off idle Reply with quote

Me thinks that too.
- not enough voltage to the ignition?
- mismatch of parts in the ignition system?
- one, or more faulty parts in the ignition system?
- too low float height?
- clogged or non functional acc pump system?
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Clatter
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PostPosted: Tue Jun 08, 2021 7:56 am    Post subject: Re: Engine stumbling badly off idle Reply with quote

Dag, stuff like this sucks.. I feel your pain my man.

I always thought the pump squirt was to make a 'blip' not stumble, and help with transition.
Even if you had no pump squirt at all,
coming on to the mains with your foot full into it,
it would stumble or cough, but then the mains would come on hard as normal.
IME the pump shot helps make things work smoothly, but it's not needed to make the car run on the mains; it'll do so after a cough, or soft spot for a second... Then run hard.
I say you can rule out the pump squirt.


The kind of thing i might have done in this situation would be to try combinations of ignition parts that weren't right, and fried things.
Like, say you had a bad ground or loose wire, then hooked up an ignition that fried the resistor in the rotor, then swapped coils to a bad one so now there's three things wrong.. Razz


I say back up and start over 100% with your ignition.
Use all the CDI stuff because that's your overall goal anyways.
Eliminate ANY possibility of a crusty/thin/inadequate/intermittent wire - be it ground or feed or ignition switch or fuse or holder..
This same "crusty little old wire" BS has plagued me from one brake light to being stranded three states away with the whole family on vacation..

While we might blame vendors or look at what we changed last, or follow best tuning procedures,
For me,
iIt's usually something little, trivial, and totally stupid! Razz
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evanfrucht
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PostPosted: Tue Jun 08, 2021 8:33 am    Post subject: Re: Engine stumbling badly off idle Reply with quote

I agree it's likely some something small and stupid, you will find it soon. It can be very frustrating... I have a tendency to find myself wanting to try to guess what the problem is, then start randomly trying different stuff with no real order to it all. Not saying you're doing this but it can be easy to fall down that rabbit hole.

Sometimes it can be helpful to just step back, ignore all your "hunches" and simply take the time to go step by step and make small changes or swap parts one at a time. It's easy to want to avoid doing than with the hope of getting lucky with a quick fix or diagnosis.

I know you know this, as do I, but sometimes I still get carried away and lost in a shit show of confusing symptoms Brick wall Laughing
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PostPosted: Tue Jun 08, 2021 8:38 am    Post subject: Re: Engine stumbling badly off idle Reply with quote

Clatter wrote:
For me,
iIt's usually something little, trivial, and totally stupid! Razz


Yep! ALWAYS!

But, those stupid, little, trivial details make it run right!

I vote you start over as well. Many times while working on drivability issues, I would detour off on the wrong path and end up scratching my head for several minutes, just stumped. At this point, I was frustrated, pissed off and desperate, for any direction. Thankfully, the guys I worked with would offer up their knowledge during lunch. It was the oldest guy in the group who told me, “Start over.” It was 2 words, out of 40 that he ever said to me. In doing so, I found the bad terminal, but that is a story for a different day.

Just reiterating the need to go back through all of it like it was your first time! If nothing else, you will have gained more confidence in what is there!
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67rustavenger wrote:
GFY's Xevin and VW_Jimbo! Smile
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67rustavenger
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PostPosted: Tue Jun 08, 2021 1:43 pm    Post subject: Re: Engine stumbling badly off idle Reply with quote

Jimbo and Clatter. I agree, it's something stupid that I am over looking.

To be clear. I dislike the "Shotgun" approach to fixing an issue.
But in this case I was up against a time crunch. Not very bright of me to think it would work out.

The goal all along is to run the CDI ignition system. It's simple and effective when working correctly.
The only reason I swapped away from it was a suspicion that it was part of the initial stumbling issue.
The engine would start. But it would not idle. Once I could get the engine RPM high enough to have the throttle open in the main circuit. The engine would be fairly peppy. But not great.

So I switched out the CDI, to the 010 points and condenser. Started with the CB dry pack. The engine would idle with this setup. But not rev as it should have.
I consulted with a current racer/builder here at work and he said to try a different coil.
This was confirmed by the mechanic that built Xevin's engine as well.
I swapped out the dry pack to the Borsch Blue and the engine seemed to respond better. I just didn't get a chance to test this setup before loading the car on the trailer.
At the race track, with the engine warmed up. Is when I discovered it was doing much the same as with the dry pack. Rev cleanly through the idle circuit. But when I roll into the transition. It acts like the fuel is not there or the ignition is crapping out.

The backfire reported earlier was caused by the shitty EMPI header to muffler flange leaking.

So I can reverse things and start over. I built in the wiring for the CDI to interface with the stock wiring for the beetle. Just incase of future trouble with the ignition systems, of either type.

Grounds are in good shape.
Carb floats are set at 5.5mm
Pump jets are functioning. I can see them squirting.
I fail to see that the current 010 point, condenser and Bosch Blue coil is a mis-match in parts.
Spark plugs were re-gapped to .028" at the ignition swap.
I would have ran the MagnaSpark. If I could have been able to raise the dist clamp stud enough to the get the nut on the CB clamp. The stud is stuck in the case.
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Clatter
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PostPosted: Tue Jun 08, 2021 3:26 pm    Post subject: Re: Engine stumbling badly off idle Reply with quote

Drive the stud sideways with a hammer to break it’s grip.
Then maybe use some heat.



I had a similar issue once and it ended up being a crusty ignition switch.
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67rustavenger
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PostPosted: Wed Jun 09, 2021 8:28 pm    Post subject: Re: Engine stumbling badly off idle Reply with quote

Ok. So I have installed the CSP EVO exhaust.

Out of curiosity. I looked down each carb throat. And indeed found that I had installed one of the AUX vents 180° incorrectly. Embarassed
Meaning, it wasn't sending fuel to the #3 cylinder.

I started the engine and it appears to rev past the idle circuit. The road test will tell the story.

I need to finish the fresh air tube installation and put the wheels back on before I drive the car.

So that's one self inflicted error. Due to rushing to get the car ready.

I'll keep at it in the current ignition configuration. Once I have it sorted. I'll move back onto the CDI ignition and see if there is indeed an issue with it.
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sled
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PostPosted: Wed Jun 09, 2021 8:43 pm    Post subject: Re: Engine stumbling badly off idle Reply with quote

Shocked Very Happy
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PostPosted: Wed Jun 09, 2021 9:41 pm    Post subject: Re: Engine stumbling badly off idle Reply with quote

👌👌👌
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67rustavenger
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PostPosted: Fri Jun 11, 2021 8:10 am    Post subject: Re: Engine stumbling badly off idle Reply with quote

So after finishing the fresh air tube installation. I took the car for a road test last night.
AH! I now have that wonderful 2180 power I expected last week.

Anyone have any idea how to reverse time one week? I'd be tickled if I could get a, "Do over" of last weekend.

Next up? Putting the CDI back in the car and getting that working as expected.
The 010 points can't keep up with the RPMs above 7K.

Thank you everyone for your input on this issue.
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