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482 does not stop
Basically having my 482 running, running and running is the best the ever.....if it was not also the case once I turn the ignition to off position.
The 482 is a Keith Craft Shelby with a quickfuel 780 and has always been flawless for 10 years. Engine has been regularly maintained and serviced. Nothing changed in set-up and now the above symptom: driving wonderful > stopping the engine > turning ignition key to off > (key function verified) > sometimes engine stops as intended but more often >engine keeps on reviving from very, very short up to 5 seconds > revs in low segment fully uncontrolled / fuel combustion’s carry on> sometimes ending with smoke leaving the hood scoope. Me behind the wheel with fear that this georgeous 482 might intend to commit suicide..... We have been searching for any fault but so far not found one Shall appreciate any hint |
That often happens when the idle speed is to high or the carb is not set up right. At idle the front throttle plates should leave 1/2 to 1/3 of the transition slot exposed in the bores. Has your carb been worked on recently or have you increased the idle speed lately. As a work around until you fix it - before turning off the key start letting out the clutch and when the idle starts to decrease, turn the key off and let the clutch out the rest of the way all at once.
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I think Dan may be correct in that you are experiencing "Dieseling" or "Run-on" It could be the carb, but if this is a new event (sounds like it) It could be cheap gas (low octane).
Ref attached article. Why does my engine still try to run after I shut it off? |
My 482 FE will run on when I use certain brands of gas but not others. Try to correlate the problem with gas brand and avoid those that cause the issue.
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I agree - it sounds like "dieseling". Can be caused by hot-spots in the head, so has the car had a lot of slow speed running/idling lately? If so, a good hard run might clear it.
Cheers, Glen |
Thanks for all the valuable advice given! Appreciated!
Fuel quality: I presume that this is an unlike cause as the engine is fed with 98/100 octane only. Carb set up change: yep, exchanged the carb as we hoped that the sympotom which was present with original carb would be abolished....no luck here - Idle speed: yep, presently in the range of 900rpm (always was past 10 years).....will decrease and see / hope Good hard run option: :) - like that one.......could be an option as I had to creep in slow traffic lately.......not impossible that „coal“ is present in the system - still: Never had that before even in hardest (slow) traffic conditions. Ignition timing: another option from my point of view as it could be a combination consisting out of several smaller effects adding up. Any advice? Before I forget: camshaft installed is Comp Cams 33-000-9 and MSD ignition module 6AL and MSD 8592...... |
That's not a big duration cam so I wouldn't think you would need to adjust the primary and secondary throttle plate curb idle positions to keep good idle response and for it to shut off when the key is killed. When you adjust the idle mixtures do you get a rich and lean roll off of idle speed or is it unresponsive to idle mixture adjustment? An idle of 900 is not particularly high either. So, you might experiment a little with timing and different fuel.
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I had a similar issue in my 468. Ran a can of sea foam in the fuel tank and it helped trenmendously. Carbon buildup can be a cause from the carbs not being adjusted as others have noted. The seam foam eats away at the carbon and blows it out through the exhaust.
Phil |
Water injection.
AEM is my favourite. |
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What can I say except: Thanks for all the valuable hints and recomendations! Really appreciated!
So, now it is up to me to fiddle around and apply / test one potential aspect after the other - I hope I can find the necessary time slot soon! Once the causes / combinations of cause is found I shall share my findings. Carsten |
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Check timing--likelyhood of advance mech hanging up and not retarding to ideal idle speed
Also maybe backfeed to ignition system from charging circuit because of poor grounds, amp guage improperly/faulty wiring--------- It probably is electrical but maybe even that is rpm related |
Check your MSD installation instructions. They address engine run on and include a diode that is to be installed between the charging light and the voltage regulator to prevent this.
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"Diesel exhaust fluid (DEF) is an aqueous urea solution made with 32.5% urea and 67.5% deionized water." Source: https://en.wikipedia.org/wiki/Diesel_exhaust_fluid "Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals." Source: https://en.wikipedia.org/wiki/Urea |
If you don't have to be hard on the brakes to blend into freeway traffic your doing the on ramp wrong!
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33-000-9 is the steel billet core that Comp Cam uses for all of their FE roller cams. You can't draw many conclusions about the duration of that cam without knowing what lobe profiles were spec'd. |
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The distributor moved and the timing g is out ..a but more advance..
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I have dealt with this a lot over the years - factors contributing to dieseling or run-on include
- increased compression ratio - increased idle speed - low fuel octane - excessive ignition advance at idle - carb rich - hot spots (in particular fouled plugs) Try lowering your idle to around 750-800 rpm, and advance to around 12 degrees max at idle, and make sure you are running unleaded premium fuel. |
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