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Old 03-15-2012, 05:17 PM   #1
mkmskm
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Default Miss and stumble that has me at wits end

I can't seem to get my car to lose a stumble on acceleration and miss when at speed. The car was a Nurex electronic ignition system until the module went out and I converted it back to std. iginition. I have checked the timing (again). All of the distributor parts were new but I have tried a second set of points, condensor, coil, heck I even put on my spare carburetor and nothing makes any difference.
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Old 03-15-2012, 05:20 PM   #2
J Franklin
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Default Re: Miss and stumble that has me at wits end

Has the distributor body been replaced also? did this happen with the EI?
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Old 03-15-2012, 05:29 PM   #3
mkmskm
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Default Re: Miss and stumble that has me at wits end

Yes, the distributor body was replaced. Actually I had just finished rebuilding a spare engine for a Speedster that I want to build and that engine had just been run on a test stand with a newly rebuilt distributor. I took that distributor and put it into my car. With the electronic ignition the car ran great.
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Old 03-15-2012, 09:47 PM   #4
1931 flamingo
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Default Re: Miss and stumble that has me at wits end

Have you ck'd the plugs, and/or fuel flow at the carb??
Paul in CT
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Old 03-16-2012, 08:59 AM   #5
mkmskm
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Default Re: Miss and stumble that has me at wits end

Fuel to the carb is fine, I checked that when I swapped the carb. I pulled #1 plug and it looked fine but perhaps I need to just replace them and see if it makes any difference. They were new last season, and worked fine when the electronic ignition was installed. It seems to behave the worst under load. It starts fine, idles fine, revs fine but accelerating in 2nd or 3rd gear makes it struggle and it doesn't run evenly when trying to cruise in 3rd, it surges.
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Old 03-17-2012, 03:09 PM   #6
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Default Re: Miss and stumble that has me at wits end

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I had same problem. It turned out to be a loose terminal screw on my ignition switch. Took awhile to figure that one out. Good luck. Bill
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Old 03-17-2012, 03:30 PM   #7
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Default Re: Miss and stumble that has me at wits end

Distr Cap cracked even a new one? Sure your points and cap have the proper gap?Rotor bad been there!
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Old 03-17-2012, 08:35 PM   #8
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Default Re: Miss and stumble that has me at wits end

Check to see that the clearance between the rotor point and contacts in the distributor body is at least .025 . Also check the coil polarity.

Over 80 percent of problems are usually electrical.

Ron
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Old 03-17-2012, 09:18 PM   #9
Fred K-OR
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Default Re: Miss and stumble that has me at wits end

I have a similar problem with my Huckster. Surges when doing 30-40 MPH under a little load. Doesn't seem like a plug miss but ??? I think I need to re-time and maybe get new plugs. It did not do this until I messed around with the timing and point gap awhile back. So if you all come up with a solution for Mkmskm I may steal the solution to try to fix mine.
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Old 03-17-2012, 10:14 PM   #10
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Default Re: Miss and stumble that has me at wits end

Check that the "strap" on the points that runs along with the spring part of the points is clearing the distributor case. Had a major problem with missing when going down the road, found that the strap was shoring out at high rpms / viboratrion. simple to fix, hours to find.

Good luck
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Old 03-18-2012, 08:44 AM   #11
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Default Re: Miss and stumble that has me at wits end

try reversing the coil polarity, then go make a test run.
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Old 03-18-2012, 10:10 AM   #12
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Default Re: Miss and stumble that has me at wits end

Interesting post.
I did a ignition seminar at the Indy Mid Hoosier Model A club yesterday discussing our new Mallory distributor for the model A and other ignition stuff.
One of the members brought his restored Model A running a aftermarket full mechanical advance distributor.
His question was how much play or slop should the rotor have with engine off. We looked at a few and it seems ( at least in my mind) they all had quite a bit .
His complaint was a surge mid throttle driving steady down the road.
A timing light shows spark moving up and down at 2000 or so rpms. Rotor can be turned by hand ( without moving the advance in the distributor) maybe 3/8 of a inch.
Any comments on whats good and whats bad doing this test.
We include a new drive rod and collar on our unit for a really close fit here....
Whats normal ???????????
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Old 03-18-2012, 07:09 PM   #13
Brentwood Bob
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Default Re: Miss and stumble that has me at wits end

Bubba, Check from the driver up to the upper end of the distributor shaft. Sounds like the teeth on the driver are worn, or there is wear at the ends of the 2 shafts. Is bushing worn?
Bob

Last edited by Brentwood Bob; 03-18-2012 at 07:10 PM. Reason: bad finger.
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Old 03-18-2012, 08:55 PM   #14
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Default Re: Miss and stumble that has me at wits end

Well I decided to pull the gas line at the sediment bowl because when I was working on the ignition I saw it drip there and tightened it. I got to thinking, I wonder since I just cranked on it, if I crimped the gas line. I pulled the line and it looked fine, but I didn't like where the ferrule was pulled it back a little and then put it back. When I drove the car the yesterday back to my garage to try and fix the ignition, low and behold it ran great. I drove it a second time later in the day, and still it ran great so I guess it was something with the gas line
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Old 03-18-2012, 10:22 PM   #15
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Default Re: Miss and stumble that has me at wits end

Quote:
Originally Posted by Brentwood Bob View Post
Bubba, Check from the driver up to the upper end of the distributor shaft. Sounds like the teeth on the driver are worn, or there is wear at the ends of the 2 shafts. Is bushing worn?
Bob
On this car it was a pretty high end rebuild with all new parts, still the play was present.
I guess my question is how much is considered proper ??? Theres got to be a spec somewhere???

By driver do you mean the oil pump driver gear ??
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Old 03-18-2012, 10:37 PM   #16
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Default Re: Miss and stumble that has me at wits end

Quote:
Originally Posted by mkmskm View Post
Well I decided to pull the gas line at the sediment bowl because when I was working on the ignition I saw it drip there and tightened it. I got to thinking, I wonder since I just cranked on it, if I crimped the gas line. I pulled the line and it looked fine, but I didn't like where the ferrule was pulled it back a little and then put it back. When I drove the car the yesterday back to my garage to try and fix the ignition, low and behold it ran great. I drove it a second time later in the day, and still it ran great so I guess it was something with the gas line
I had to fix a similar problem on a car last year. I had to move the ferrule more to the end of the pipe, and tighten it properly. The ferrule wasn't properly tightened and the fitting was full of teflon tape, which was blocking the fuel flow. If you were able to move the ferrule, it wasn't properly tightened in the first place.
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Old 03-18-2012, 11:21 PM   #17
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Default Re: Miss and stumble that has me at wits end

Both my A,s have about 1/8" backlash on rotor & run perfect.Some will have over 1/2" play,& still run.The dist-pump drive gear will often have the teeth worn to a knife edge & worn out drive tangs,same with dist shafts.The drive gear on cam can also be worn.There are oversize gears available in,I believe,.004 & .010 OS to make up for a worn gear on cam.
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