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 Post subject: Re: acceleration issues
PostPosted: Fri Apr 29, 2016 10:14 am 
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Joined: Sun Nov 07, 2010 5:31 pm
Posts: 40
Location: Reading, Pennsylvania
he steve, i figured out what that noise filter was and i just tossed it in a box in the garage since i dont even use the radio. and yes, she has dual points. upon visual inspection of the points, they looked fine, no burning, pitting or corroding. so i put the correct socket and breaker bar on the crank pulley and rotated the motor until each set of points was at the peak of the rotor and check for the .017 gap which is required by the manual, they were both off, so i loosen each in turn and adjusted them so that the feeler barely dragged between the points. i put her back together, fired her up, and it ran rough again, back fired when the throttle was blipped and idled rough. so then i grabbed a timing light, hooked the lead between the dizzy and plug number one, which, im assuming is the front most, drivers side cylinder, correct? i hooked the leads of the light up to the battery of the car rather than a seperate 12v battery, and although the light was a bit dim, there was no trouble viewing the timing in broad daylight. so, this timing test brought about some other questions, answers for which i couldnt find in the manual such as the timing marks on the dampener. i see the DC mark, and i see the marks for 10 degrees advanced, and 10 degrees retarded, but i wasnt sure which was which. i assumed that the 10 mark counter clock wise of the DC was advanced, due to engine rotation, but im not sure. either way, it seemed as though timing might have been off a bit, though not enough to cause the recent issues. so in trying to fix the issue, we loosened the dizzy and spun it in the direction that gave us a slightly higher idle, which told me we were advancing the ignition, which, as per the timing light, and our assumption of the timing marks, was where we needed to go. it was a major pain in the ass to adjust that and tighten it by the way and i may have gotten zapped...at least once. anyhow, since we arent sure of exactly how we are adjusting the timing, we stopped there. we did fiddle a bit with the carb adjustments, but to no avail. i ran out of daylight but i think im going to just change out the points and condensor all together as had been suggested from the start, this way i know that portion is mechanically/electrically sound, then i can move on to fueling issues. i know that i dont have to take the dizzy out to change out these items, but it seems like it is going to be a pretty big pain in the ass do do it all in place, what with those small screws, their sideways orientation, and the location of it all. to adjust the dizzy itself i needed a stubby wrench and had to lay completely across the fender with my legs in the air! i cant see it being very easy without loosing screws or parts, however, i do understand that taking the base out can provide other issues so perhaps ill just bite the bullet and get it done inside of the car. so can anyone tell me interpolation of the timing marks? and i believe that the timing should be 10 degrees BTC correct? thank you

josh


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 Post subject: Re: acceleration issues
PostPosted: Fri Apr 29, 2016 7:10 pm 
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Joined: Thu Aug 26, 2010 7:00 pm
Posts: 390
http://www.ebay.com/itm/1955-DeSoto-EIG ... ap&vxp=mtr

Get one of these tune-up cards. I think it would be a great help. I have a 56 Tune-up card, which is similar but not exactly the same.

Thanks
Steve


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 Post subject: Re: acceleration issues
PostPosted: Sat Apr 30, 2016 2:49 am 
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Joined: Mon Jun 03, 2013 10:01 am
Posts: 221
Josh -

IMHO, you need to take a more 'scientific' and less 'scattershot' approach to solving the issues with your Desoto.Throwing endless parts at the car, hoping that one will solve the problem, is not a good approach.

First, focus on the rough idle problem. A vacuum gauge is an excellent tool for diagnosing engine problems. In fact, I recommend setting the timing based on the reading off that gauge. If you've never used one, there are lots of videos on YouTube showing all the engine tests you can do. Or just google it.

To loosen your distributor you need a distributor wrench. Here is the one I purchased on ebay:

http://goo.gl/DNSMZj

Once you have worked out the idle problem, then turn to the carb. You said you bought a new carb. Is it the correct one for your car ? Did you verify the Carter number as what is in the shop manual or AEA Tuneup card ? Then once it was on the car, did you set the fast idle, slow idle and mixture screws ? You don't do yourself any favors by 'fiddling' with the carburetor.

I'm also of the opinion that the condenser might be bad, which may be causing the backfire. I would also verify that the spark plug wires are not crossed.

Ron


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 Post subject: Re: acceleration issues
PostPosted: Sat Apr 30, 2016 1:05 pm 
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Joined: Sun Nov 07, 2010 5:31 pm
Posts: 40
Location: Reading, Pennsylvania
ron, some would call my method more elimination in nature rather than "scattershot" i saw no need in replacing parts that were not defective and thus possibly causing more harm or problems than good in the process.
if you recall, the rough idle was not an initial symptom, in fact, the car never really had a poor idle. perhaps a miss here and there, but nothing very noticeable, so this was not on my radar for a symptom to repair.
as for the vacuum testing, i will certainly give that a whirl, however, im still unsure how to decipher the timing marks on the dampener, might someone elaborate on this?
as for the dizzy wrench, thanks for the tip, i can make one of those easy peasy.
as for the carb, i bought it as an NOS and it was never used but old at that point. it was an improvement over what i had on the car, which is not to say that it ran properly from the start, however, my machinist and i set it up to run perfectly well, sans the accelerator pump, and that is how it ran for several years...and a ton of miles might i remind you. again, these issues only started recently and the carb is definetly suspect, but not where i wanted to start my diagnosis. perhaps this was where i started on the wrong foot. but replacing or rebuilding the carb seemed a large step to take if i found more obvious issues in the ignition system. we only "fiddled" with the carb settings once we thought we had the timing set, the points gapped, the plugs cleaned and gapped, and the new rotor and cap on, and only to see if we could smooth out the idle, which had changed at that point from correcting the timing.

i will be ordering one of those AEA tune up cards. its certainly better than continually referring to the manual which is what ive been doing.

thanks for all of the recommendations.


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 Post subject: Re: acceleration issues
PostPosted: Sat Apr 30, 2016 4:18 pm 
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Joined: Thu Aug 26, 2010 7:00 pm
Posts: 390
Josh

I just took a pic of the timing marks on my '55 Firedome. So you can see the pointer at about TDC or O degrees. You can also see the 10 after and 10 before TDC marks. So the BTDC (before top dead center) marks are the ones ahead of the zero in the direction of rotation. In this picture and on your car, that would be closer to the floor.

I was once a mechanic at a Chrysler Plymouth dealer. If I had a no start or hard start car to recover, I put 2 things in my pocket. A condenser and a ballast resistor. These were the most common causes of problem, and the cheapest to fix. Since your 6V car has no ballast, the condenser is the first thing to replace. It doesn't matter what it looks like!

Good Luck!
Steve


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