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 Post subject: acceleration issues
PostPosted: Sat Apr 16, 2016 1:05 pm 
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Joined: Sun Nov 07, 2010 5:31 pm
Posts: 40
Location: Reading, Pennsylvania
ok everyone, so here is a brief description of what i am going through...i have a 55, 291 firedome which i drive everyday, that is, when she isnt down here and there for the myriad of issues that i have to fix due to driving a car of this age all the time. years ago when i first bought her, she had a similar problem to what im experiencing right now, poor acceleration, frequent misses, etc. so one by one i began to replace items, i started with new plugs and new taylor wires, then an NOS carb that i found which was said to be rebuilt a long time ago but had no proof of that, but it was a good price, and was better than what i had, then the fuel pump went out on me, so i had andy bernbaums rebuild it. installed that and besides a crappy accelerator pump, which i pushed through every day, she ran relatively well. now she is going back to the same symptoms. at low gear and tooling around at low speed, she doesnt miss much, but the second she has load, or i try to accelerate quickly, she breaks up badly and even back fires. so i pull the plugs, most looked good, one was covered in oil...no surprise there, checked the gap, regapped and cleaned them, checked the wires, saw nothing out of the ordinary, and buttoned her back up but no luck. so here is where im at. i know that i really need to take the cap off and check the points...something im not very familiar with, but i can follow the manual. but in doing some reading of the manual, as i often do, i came across other items that may be and issue and im wondering if i should check them and how often these things are an issue, especially regarding my issue. such as the exhaust manifold heat control valve, etc. ancillary things which might not be obvious but may be symptomatic on these cars as i have no familiarity on any other desoto vehicles other than my own. other questions i had was the possibility of debris in the fuel line, as i understand it, the only "filter" is inside the tank, which has to be completely dropped in order to check/replace/service. so is it correct that there is no other fuel filter on the firedome, no inline, etc? also, how would i be able to check for a blockage? i understand that i can to a pressure test, but as i understand it, this test is more for diagnosing a fuel pump failure or issue. and i dont believe that i have a fuel pump issue as it was just rebuilt, and i do plan on testing the pressure, but id rather put my effort into other tests that seem more likely. my next likely culprit is the carb. so, correct me if im wrong here, but it seems that diagnosing carburation, is nearly a lost cause, as any diagnosis requires tearing the unit down for inspection, and thus a rebuild is, or should be necessary anyhow...correct? so my mind then goes to either rebuilding my carb, which i have never done, finding another used or NOS one, which is difficult to find at best and, as i have done before, is a shot in the dark as to whether or not ill get a good one, or, and what im thinking most, is to find another, more common carb that i can use which wont result in having to convert things such as the intake manifold, etc. btw, she has the single barrel carter.
i do apologize for the long winded, scatter brained method of this post, however, i have about 30 minutes a day where i dont have two small children trying to kill me in one way shape or form, so im just throwing all of this out of my head to get it out there.
help me get my baby back on the road. every day that goes by where i can drive her is a sad, depressing day.
and just for your viewing pleasure, my 4 year old loves to work on her with me and insisted on helping to remove the spark plugs...

Image

thank you for your help, it is greatly appreciated. anyone trying to contact me directly can do so at BAMBAML19@GMAIL.COM

Josh


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 Post subject: Re: acceleration issues
PostPosted: Sat Apr 16, 2016 3:47 pm 
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Joined: Fri Jan 30, 2015 10:57 pm
Posts: 212
Timing? If it's not in the carburetor (accelerator pump) the timing may be off. Clean (file) or replace the points, adjust the gap, and set the timing.

Today's ethanol in gasolines have an adverse effect on old (prior to the early 1980's when ethanol started to be added) rubber components in the fuel system - makes the rubber sort of mushy and deformed. Especially the fuel pump diaphragm and carburetor components. You may have to rebuild or replace the carb and fuel pump.

Good luck and keep us posted with your success.

"It's delightful, it's delovely, it's DeSoto"


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 Post subject: Re: acceleration issues
PostPosted: Sun Apr 17, 2016 12:07 am 
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Joined: Sun Nov 07, 2010 5:31 pm
Posts: 40
Location: Reading, Pennsylvania
Thank you for your suggestions fred. i doubt its the fuel pump since, according to bernbaums, all their replacement gaskets which they use to rebuild fuel pumps, are compatible with todays fuels. and question...how would the timing all of the sudden be off?


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 Post subject: Re: acceleration issues
PostPosted: Sun Apr 17, 2016 2:30 am 
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Joined: Fri Jan 30, 2015 10:57 pm
Posts: 212
Timing may be OK but worth a check. The timing chain could stretch and throw the timing off but the points could be a big part of the problem too if they are bad and not properly gapped. Coil could be bad - there are many possibilities and they all have to be checked out. Also make sure the wires go to the right plugs 1-8-4-3-6-5-7-2.

Keep at it and you'll get it I'm sure. Good luck!

"It's delightful, it's delovely, it's DeSoto"


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 Post subject: Re: acceleration issues
PostPosted: Sun Apr 17, 2016 4:20 am 
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Joined: Mon Aug 09, 2010 6:43 pm
Posts: 825
Josh,

I've owned a '55 Firedome for over 30 years and drive it regularly but not as a daily driver. I've experienced similar drivability issues over the years but a very similar situation occurred last fall. It was stumbling under load and eventually backfired and became difficult to start or run. It died on a busy road, we got to a parking lot and I had it towed to a local old car friendly garage. They checked all the things you have checked and even sent the fuel out to be tested. Everything checked out good aside from cleaning out a lot of carbon. On the way home from the shop after they thought they cured the problem the car again stumbled under load. The fuel pump was relatively fresh but in desperation my buddy and I changed the fuel pump and took the car long distance to a car show with no issues then or since. To Fred's point, fuel pumps just don't last long these days with today's fuel. Terrill Machine will rebuild your pump for less than Bernbaum and turn it around in 2 - 3 weeks.

Good luck!

Mark


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 Post subject: Re: acceleration issues
PostPosted: Sun Apr 17, 2016 12:29 pm 
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Joined: Sun Nov 07, 2010 5:31 pm
Posts: 40
Location: Reading, Pennsylvania
thank you fred, i will check the timing and the points. again, i appreciate the advice.

mark, thank you for chiming in, i sure wish i had a spare fuel pump to swap out so that i dont unnecessarily pay for a rebuild that i may not need...but then again, im probably hedging my bets if i do since i do drive her daily. do you have the answer to my question on the fuel filter? did you install an after market one? ive never seen a car without one inline and with as old as the car is, im sure there is plenty in the tank to get sucked into the lines/carb, etc.

thanks everyone.


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 Post subject: Re: acceleration issues
PostPosted: Sun Apr 17, 2016 1:25 pm 
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Joined: Thu Aug 26, 2010 7:00 pm
Posts: 387
Don't do anything else until you replace the condenser.

Then report back!

Have a nice day
Steve


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 Post subject: Re: acceleration issues
PostPosted: Mon Apr 18, 2016 2:03 am 
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Joined: Mon Aug 09, 2010 6:43 pm
Posts: 825
Josh,

There is no fuel filter on the car from factory other than the filter/strainer in the fuel pick-up in the tank. Many cars of the era - mine included - had a glass sediment bowl with filter on the bottom of the fuel pump. Not sure it that was factory equipment but such a pump was on my car in the early '80's when it was purchased with 32K miles.

Mark


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 Post subject: Re: acceleration issues
PostPosted: Mon Apr 18, 2016 11:41 am 
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Joined: Fri Jun 10, 2011 8:52 pm
Posts: 115
Josh,
I noticed that you have not yet become an NDC member. As I recall, we have covered similar complaints both on this forum and in the DeSoto Adventures magazine (comes with your NDC membership at no additional charge).
Most likely, your coil is breaking down under a load. Over time the insulation separating the windings breaks down short circuiting the current flow among the the primary and secondary wires individually and collectively vastly reducing the voltage produced necessary to accelerate under a load. While this my feel like fuel starvation, it is in fact insufficient voltage to fire the plugs under load.
Try a new coil and let us know how it worked out.

Geoff Overley, Editor
DeSoto Adventures Magazine
desotoadventures@gmail.com


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 Post subject: Re: acceleration issues
PostPosted: Tue Apr 19, 2016 10:41 pm 
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Joined: Sun Nov 07, 2010 5:31 pm
Posts: 40
Location: Reading, Pennsylvania
thank you geoff, i will look into the NDC and i will try out the coil. i am going to be ordering a tune up kit, consisting of a new cap, rotor, condensor, and points, and ill had a new coil to the order. at this point it cant hurt, and its probably due for replacement either way. hopefully ill get a chance to get this all swap out within the next week or so. ill post an update. thanks again everyone.

Josh


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 Post subject: Re: acceleration issues
PostPosted: Tue Apr 19, 2016 11:41 pm 
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Joined: Thu Aug 26, 2010 7:00 pm
Posts: 387
NDC member or not. condenser is your likely culprit.

Good Luck
Steve


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 Post subject: Re: acceleration issues
PostPosted: Sat Apr 23, 2016 4:04 pm 
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Joined: Sun Nov 07, 2010 5:31 pm
Posts: 40
Location: Reading, Pennsylvania
well, i ordered a new condesor, cap, rotor, points, and coil. hopefully ill be able to install everything tomorrow and see if this has remedied the situation. any tips on replacing these components other than referring to the service manual? thanks.

Josh


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 Post subject: Re: acceleration issues
PostPosted: Sat Apr 23, 2016 7:13 pm 
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Joined: Thu Aug 12, 2010 4:09 pm
Posts: 76
Josh: This is rich Hartung and I live off of route 422 in Audubon, PA. I have a 39 Desoto. Let me know if you get the car working with the new components.

Hope you join the NDC and possibly come down to the convention that is being held in Timonium Md just outside of Baltimore in July.

Rich Hartung
Desoto1939@aol.com


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 Post subject: Re: acceleration issues
PostPosted: Sun Apr 24, 2016 2:05 am 
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Joined: Sun Nov 07, 2010 5:31 pm
Posts: 40
Location: Reading, Pennsylvania
hi rich, i hope to be able to meet you at some point in the near future.

so, today i thought id just change out the coil as it would be the simplest replacement. so first off i noticed as i removed the old one, that there seemed to be some sort of condesor pinched between the mounting tab and the actual bracket that attached the coil to the top of the manifold. it was connected to the negative terminal of the coil. i wasnt sure what this was as it isnt anywhere in the manual, so i just reinstalled it as it was. i also noticed that the bracket that was on the old coil was not removable and thus i was not able to attach the new one in the same fashion. of course, i can make my own bracket, but this wasnt the point. so i hooked everything back up an tried to fire her up to no avail. at this point i wondered if the coil, or this condensor looking piece needed to be grounded or physically attached the the manifold, but this made no sense to me as the connectors on the coil meet the requirement for power and ground. so then i took the old cap off, and had a look inside and it looked as though everything was fairly new, even though ive owned it for more than 5 years and never changed these items out. i saw nothing odd, no burning, scorching, pitting, or anything else out of the ordinary. no, i didnt use a feeler gauge to actually check the gap. the condesor also looked brand new. i swap out the old rotor and the old cap for the new ones and left the points and condensor in place. again i tried to start the car but nothing. i check my wires to make sure they were clipping on properly and the coil wire was a bit tough to know if it was seating in the coil properly, but i thought it was good...perhaps not as the car wouldnt start again. i couldnt figure out what was going on and it was getting dark so i thought i would just put everything back the way it was and see if i could get her started again to make sure something else didnt happen during the removal of these items. once i get everything back to the way it was, she started, after a long crank, but she started, but ran very rough. i could tell she was missing on at least one cylinder, if not more, but with the car running, i removed each plug wire from the spark plug and pointed it towards the block to confirm that it was in fact firing and they all arced properly. i tried to drive the car down the block but i barely got a block away and turned back. im wondering if i got the wrong coil and im wondering what this condensor thing was connected to the coil. i ran out of light so i packed it in for the day. im going to try to check the timing tomorrow, but i was wondering, do i need a special timing light for a 6 volt car? anyone else have any idea about the flurry of stuff i just posted? im thinking i just need to take the dizzy out and change everything out just to be sure but i think its odd what happened and id like to get another take on it. thanks everyone.

Josh


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 Post subject: Re: acceleration issues
PostPosted: Sun Apr 24, 2016 11:16 am 
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Joined: Thu Aug 26, 2010 7:00 pm
Posts: 387
The condenser looking thing attached to the coil is a radio noise suppressor.

Yes, you must use the feeler gauge to gap the points. Dual points? Correct?

Any time you mess with the distributor, you must check the timing. Put a 12V battery near your car to power your timing light.

Did you remove any plug wires from the distributor cap? If so, did they go back on in the right spot? Rough running could be caused by crossing the wires.

The points and condenser can be replaced without removing the distributor.

I recommend you replace the condenser before you do anything else, again.

Good Luck
Steve


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