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  #1   IP: 69.156.147.234
Old 07-07-2019, 03:09 PM
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Runs with choke only ... mostly

Ok, it seems to be my turn for this kind of problem, and I hope it is something simple that I just dont know enough about.

The engine this spring has been toyed with a little in terms of idle mixture and power tuning at idle.

Started the engine today (starts as expected with choke and throttle ) and after a min closed the choke and let it warm up around 1200-1500 rpm. After around 10 min it started losing power and then died.

Restarted with choke on and it would take enough throttle for it to run around 2500 rpm, eventually climbing to 3000 if I did nothing. With the choke on, if I reduce throttle it dies.

About 10% of the time, I can get the choke off and the engine running around 2000 rpm for a min or two, then it will lose some power, come back, but eventually dies within that time frame.

The carb choke opens and closes fully - VISUALLY checked

The idle mix is at 1.25 turns

Fuel pressure is constant at about 2.5 psi

During the brief times it runs, the vacuum is at 15

I did not have a fuel safe container to check fuel from carb, etc. With me.

Time to remove carb and clean?

Could it be water causing this? Time to hook up another fuel source and see if any different ?

I'VE BEEN trying to search all the tidbits of info on here but would appreciate any input.
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Old 07-07-2019, 04:01 PM
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First guess from me; carb float.*

*NOT a qualified opinion
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Old 07-07-2019, 07:17 PM
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Quote:
Originally Posted by GregH View Post
The engine this spring has been toyed with a little in terms of idle mixture and power tuning at idle.
Can you give us more detail on what you did?

Have you cleaned or rebuilt the carb in the recent past?
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Old 07-07-2019, 08:32 PM
JOHN COOKSON JOHN COOKSON is online now
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Could be a weak spark plug. Pull the spark plug wires one at a time while the engine is in the "low power" mode and note any changed in performance.

Could be a blocked tank vent. Would explain the 10 minute normal run time. To diagnose loosen the fill cap.

More as I think on this a bit more.

TRUE GRIT
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Old 07-08-2019, 07:07 AM
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Quote:
Originally Posted by roadnsky View Post
Can you give us more detail on what you did?

Have you cleaned or rebuilt the carb in the recent past?
No since spring 2018, it has been working fine and now this year I'm trying to tweak things.

The engine was running rich last year. Start in 2sec on choke, choke off right away. Plugs very dirty end of season.

Backed off idle mix 1/4 turn this spring and played with distributor to get the roll pin at zero mark and from there a little adjust for idle rpm.
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Last edited by GregH; 07-08-2019 at 07:14 AM. Reason: More info
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Old 07-08-2019, 07:09 AM
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Quote:
Originally Posted by JOHN COOKSON View Post
Could be a weak spark plug. Pull the spark plug wires one at a time while the engine is in the "low power" mode and note any changed in performance.

Could be a blocked tank vent. Would explain the 10 minute normal run time. To diagnose loosen the fill cap.

More as I think on this a bit more.

TRUE GRIT

I did try the open deck fill and no difference. The fuel pressure gauge always around 2-3 psi
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Old 07-08-2019, 08:33 AM
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The symptoms point to an inadequate fuel/air ratio so what are the possibilities? Partially clogged main jet, intake vacuum leak, fuel contamination, fuel level low in the bowl. Do you have a PCV system? If so, check it for leaks and proper valve operation.

However, there was one other thing you said:
Quote:
The engine this spring has been toyed with a little in terms of . . . . . power tuning at idle.
If by tuning you mean adjusting the timing, there is a directive from Universal about power timing at idle but the preferred method by far is to power time at greater RPM with the advance fully engaged. My earlier power timing efforts were at idle but checking it carefully a few years ago with a timing light showed it was grossly advanced. Getting it right made a huge difference in performance.
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Last edited by ndutton; 07-08-2019 at 09:08 AM.
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  #8   IP: 192.186.122.174
Old 07-08-2019, 12:57 PM
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Quote:
Originally Posted by ndutton View Post
The symptoms point to an inadequate fuel/air ratio so what are the possibilities? Partially clogged main jet, intake vacuum leak, fuel contamination, fuel level low in the bowl. Do you have a PCV system? If so, check it for leaks and proper valve operation.

However, there was one other thing you said: If by tuning you mean adjusting the timing, there is a directive from Universal about power timing at idle but the preferred method by far is to power time at greater RPM with the advance fully engaged. My earlier power timing efforts were at idle but checking it carefully a few years ago with a timing light showed it was grossly advanced. Getting it right made a huge difference in performance.
I've got my timing light along. When I started this "playing" around the roll pin was showing up a good 10 degrees to the left of the mark (too retarded?) on the flywheel cover. It was adjusted to be as centered as possible using that reference. I'll start there this evening.
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Old 07-08-2019, 02:54 PM
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hmmm, I wonder when you did the "power timing" relative to this recent "running only with choke" issue?

If you did the timing well before this recent episode it might be wise to leave it as is until you find out what is causing the engine to only like to run with a lot of choke.

Once that is resolved, then check the timing.

Otherwise you risk conflating the two issues.

I experienced similar symptoms - would only run with a lot of choke - and the problem for me was related to dirty fuel. Changed the filters and removed the tank and had it cleaned - problem solved.

Peter
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Old 07-09-2019, 08:25 AM
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Quote:
Originally Posted by Peter View Post
... and the problem for me was related to dirty fuel. Changed the filters and removed the tank and had it cleaned - problem solved.

Peter
And there's the solution! Way too much water (let along ANY) in the fuel which is 1000% my fault from last fall's haulout and not securing the deck fill cover properly with the following 24hrs of rain.

Time to drain and see what can be salvaged of 18 gal.

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Last edited by GregH; 07-09-2019 at 08:28 AM.
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Old 07-09-2019, 12:11 PM
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I would burn any "salvaged" fuel in my old car or truck, not back in the a4. Volume of fuel burned and larger passages in the system
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Old 07-09-2019, 01:02 PM
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Old story I've told here before - -
A few decades ago I joined a group for a SCUBA trip to Ensenada, MX, camped at an area known as La Bufadora. We brought two Zodiacs for offshore excursions. One of them got swamped with the outboard tank vent open, soured the fuel and the engine died. Back on shore I asked the owner what he planned to do with the contaminated gas. He said he would give it to a local for his campfires.

I asked for starting them or putting them out?
(always the wise guy)
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Old 07-09-2019, 03:30 PM
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I bought a new toy which may help a few folks needing to drain their tanks. My old Morgan, similar to Alberg, has the tank just below the cockpit more or less to the rear and above the engine with a cockpit fuel fitting. When I got some water in the tank I used a Terra "stick" pump from Amazon [on ebay as well] It operates on two D cells, has a 17 in telescopic wand and a 3ft drain hose with a handle switch. Pumps out @ 2 1/2 gal/min. Mine was about $40 but their are other brands/models as low as $12. Not the most robust built pump I have seen but then I do not plan on using it all that much. Only drawback is my specific one has the wand pump end just slightly larger than a standard US gas can opening - can't use it for pumping gas directly from a can into the tank without some modification. Getting tank gas out is a breeze.
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Old 07-09-2019, 04:30 PM
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Quote:
Originally Posted by Sam View Post
I bought a new toy which may help a few folks needing to drain their tanks. My old Morgan, similar to Alberg, has the tank just below the cockpit more or less to the rear and above the engine with a cockpit fuel fitting. When I got some water in the tank I used a Terra "stick" pump from Amazon [on ebay as well] It operates on two D cells, has a 17 in telescopic wand and a 3ft drain hose with a handle switch. Pumps out @ 2 1/2 gal/min. Mine was about $40 but their are other brands/models as low as $12. Not the most robust built pump I have seen but then I do not plan on using it all that much. Only drawback is my specific one has the wand pump end just slightly larger than a standard US gas can opening - can't use it for pumping gas directly from a can into the tank without some modification. Getting tank gas out is a breeze.
I do like the Terra's (and have a couple) but my tank has been moved to the starboard lazarette locker and so the fuel fill line now has 2 90 degree bends! I certainly don't make it easy to help myself
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