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Help with 340 diagnosis - FIXED
#1654891
08/04/14 12:54 PM
08/04/14 12:54 PM
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Joined: Feb 2003
Posts: 1,228 Maple Valley, WA
70mopes
OP
pro stock
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OP
pro stock
Joined: Feb 2003
Posts: 1,228
Maple Valley, WA
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My 70 340 is built stock and was running good. It has less than 200 miles on it since restoring my car.
during previous drives, I noticed a stumble/hesitation on accelerating after releasing the throttle at cruise and re-applying gas. Figured I'd fix the car later as it was not that big a deal.
Yesterday I had a friend out in it and it began to stumble repeatedly. I could not tell if it was a fuel or ignition thing. The carb has never been very sensitive to idle adjustments (factory AVS). It would stumble when driving and while idling... almost as if trying to cut out and then kicking back in.
Took the AVS off and found a bad float. I replaced that and reset the floats. When I went to start it it would not run at all. It would run, then suck air and try to die... kick back in and then do the same thing.. laboring to run but trying to die. I could not keep it running much less idling. I took the AVS apart again... cleaned it again, made sure the floats were adjusted right put it back on with the same results.
I changed the coil... no change. I pulled the distributor and checked the points gap that was OK. It seems like carburetion since it is the only thing I handled. I have rebuilt a lot of AVS's and have worked on so many engines but have never had a motor run like this - especially all of a sudden.
Any ideas sure would be appreciated.
Thanks
Last edited by 70mopes; 08/05/14 01:11 PM.
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Re: Help with 340 diagnosis
[Re: 70mopes]
#1654892
08/04/14 01:43 PM
08/04/14 01:43 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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I would shoot a 2 second blast of starting fluid into the (2) idle mixture screw holes (need the thin red straw to do a good job on this) & if that ain't it then I'd open the carb up again paying attention to gasket condition (vac leaks) & I'm assuming you have a good AP squirt (& immediate tip in) when the throttle barely moves. Holler how it turns out
live every 24 hour block of time like it's your last day on earth
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Re: Help with 340 diagnosis
[Re: Baxter61]
#1654894
08/04/14 02:31 PM
08/04/14 02:31 PM
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Joined: Feb 2003
Posts: 1,228 Maple Valley, WA
70mopes
OP
pro stock
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OP
pro stock
Joined: Feb 2003
Posts: 1,228
Maple Valley, WA
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It was running and idling prior to taking the carb off - with the miss/stumble I previously mentioned.
When the AVS was apart, I sprayed the idle holes with carb cleaner and witnessed a nice blast through them. Cleaned all ports and emulsifier tubes. I had pulled the distributor to check the point gap and re-installed it. It had to be a few degrees off but not enough to cause it to run like this.
It runs than dies out... kicks back in and then dies out again. I can't keep it running at idle or past the idle circuit which is strange for an AVS. Checked vac leaks etc. That isn't it. It almost seems as though I am intermittently losing ignition.
Last edited by 70mopes; 08/04/14 02:32 PM.
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