A stumble and a rough rumble... on acceleration

[48ratrod]

Hey gents.... 

 

I NEED your collective wisdom!

 

From the Vancouver, BC area...

 

Have a 48 Plymouth that I pulled out of storage recently because I finally had room in the garage.    

Took a while to get things fired back up - replaced the points, condenser, spark plugs battery & timed things up.

 

I also knew the carb needed some work - bought a rebuilt online - and was going to replace it and clean up the other - thinking it can't be bad to have another around anyways.  

Didn't have it yet when I got the car running - but was on my do-list when it arrived.    

 

Drove it a bit over a 2 week period of time - seemed to be doing fine... was heading over to a friends one day - and all of a sudden it started to stumble, run really rough on the higher end of acceleration in all gears.  This was a new one to me.    Thought maybe it was an issue with dirt &/or rust clogging things up in the fuel system.  Got it to my friends – over the last two weeks have clarified I think mostly that its not the fuel system – (emptied the tank – its clean, blew the lines clear, checkout/replaced fuel pump, have new fuel filter before the carb and have since installed the rebuilt carb) – SIDE NOTE : Examined the new plugs I put in and all were black & sooty

 

Went back to check ignition and timing

rechecked the distributor:

- found I had forgotten to replace the lock screw for the points – thought maybe that could have caused problems if road rattle had caused the points to get out of wack…appears not as replaced the screw and set things in place.  

 

Replaced wire running from coil to the distributor

 

Ran a compression test

Test 1 –     100,  95,   95,  105, 100, 95

Wet test – 110, 105, 105, 115, 105, 105

 

Ran a vacuum test as well – it was on the lower end at 17 more or less steady – slight vibration on the reading.

 

Replaced all spark plug cables with new ones.

 

Trying to work to spec so have adjusted RPM’s to about 500 rpms – but I think its better just over 600rpms -  never hear the stumble or roughness during idle.

 

Points have been set to approx. .20 to start the timing process.

 

Timing adjustments have been at TDC – although after combing the site over the last 2 weeks have adjusted that to about 3 degrees advanced of TDC.   

 

QUESTION - have used a timing light (innova 5668 - http://www.amazon.com/gp/product/B000EVU8J8/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1) I know that this is a 12volt light – have used it on both the 6 volt system and another 12 battery – I get the same numbers for everything (tach, timing function) except for dwell – thoughts?  

 

- Speaking of DWELL – dwell was off quite a bit - sitting way to low on both voltage numbers (6v & 12v measurements) – so I thought I would still adjust it incrementally and see what sort of improvements take place.  The measurements when I'm taking them -  also seem to fluctuate pretty dramatically  from low 20’s to as high as 59 BUT from the best I can determine currently Dwell is sitting at 38 degrees … but who knows

 

I have another automotive  multimeter (dwell and tach included) from NAPA that I bought to test it against the innova - both the tach results and dwell don’t resemble even remotely any of the numbers I’m pulling from the Innova light – on all cases I’ve made sure settings for dwell and tach diagnostics are correct for 6 cylinders and are connected to the neg post on the coil.   

 

After doing what I could at my friends place – believe me – he’s a good guy I left pretty disheartened last night – still have this stumble and roughness every time i begin to accelerate in any gear - but am determined to figure this out - not by myself though - that's plainly apparent.   

 

Am heading out there again today to see what else I can do … will  share the latest vacuum results I’m going to take.  

 

Wondering about the vacuum advance and checking that out – have been reading here and it always seems to be a bit of a culprit in these kind of scenarios – I’m going to pick up a vacuum pump – have a gauge of course – but I see to check this out at the distributor I need one of those. 

 

Please…Help put me out of my misery…

Edited August 28, 2014 by 48ratrod

[Niel Hoback]

Variable dwell usually means a worn distributor bearing.  Wiggle the rotor to check for excessive side play. Make sure your points are clean and flat. And not made in China.

[_shel_ny]

There was a similar case here recently. There was an issue with new points. Spring was not putting enough tension on the points at higher rpm's.

[Don Coatney]

What are you using for a carburetor air cleaner? Is it clean and not restricted?

[48ratrod]

Neil - Thanks - will check the side play out - does something like that just happen or is it just a matter of the ol' straw on the camel's back? 

 

Shel_ny - Yes ... I read that posting too - I've picked up another set of points, just in case - haven't got to that stage yet - have to check if they're from China

 

Don - Using a paper air cleaner - its pretty good... 

[Don Coatney]

Post a photo of your paper air cleaner.

[Niel Hoback]

Bearings wear with mileage. There's a cup on the side of the distributor that's supposed to be filled by the maintenance schedule.

[48ratrod]

Don... will do when I get there.

Don ... pics for you

Edited August 30, 2014 by 48ratrod

[ptwothree]

Check the voltage at the coil from it's source.....should be at least be 6+ volts when the engine is running.

[soth122003]

I have the same problem. Turns out my genny was not charging the battery. As the battery got lower on charge the engine would sputter and spit at high end rpm's in all gears. The genny is in the shop being rebuilt now and I will update if this has fixed the problem when I get it back and installed.

 

Joe

[desoto1939]

Here is another idea, Check the distrubtor breaker plate. These do wear and then get sloppy and when this happens the point can drift.  I like to always install a breaker plate when doing a tuneup. This way I can setup the breaker plate with all of the appropriate items and then just install the new unit and then make the appropriate adjustements.  I then rebuild the old breaker plate with new parts if the unit is still good and does not have any slop.

 

Just a thought to check.  ALso as mentioned before could also be the bearing inthe dizzy that is worn.

 

Rich HArtung

Desoto1939@aol.com

[1941Rick]

What brand of plugs are you using.....seems that Champion work best in these engines.....ask me how know.

sounds like you are in the right area, the distributor.

[Don Coatney]

Champion spark plugs would be my last choice. There are a lot of folks on this forum who have had bad luck with Champion plugs myself included.

[BigDaddyO]

When installing new points, remember to put a dab of grease (about the size of a match head) on the wear block of the points.

[Niel Hoback]

I find Champion plugs good for distance. I put Chryco plugs in my car and I can throw Champions farther than any other brand.

[48ratrod]

Check the voltage at the coil from it's source.....should be at least be 6+ volts when the engine is running.

thanks for the suggestion… Voltage from the coil is fine… Running at 6.5… New coil put in when I pulled it out of storage.

[48ratrod]

I have the same problem. Turns out my genny was not charging the battery. As the battery got lower on charge the engine would sputter and spit at high end rpm's in all gears. The genny is in the shop being rebuilt now and I will update if this has fixed the problem when I get it back and installed.

 

Joe

hey Joe… Check the generator… Everything is A-OK there too - was rebuilt not that long ago as well.

[48ratrod]

Here is another idea, Check the distrubtor breaker plate. These do wear and then get sloppy and when this happens the point can drift.  I like to always install a breaker plate when doing a tuneup. This way I can setup the breaker plate with all of the appropriate items and then just install the new unit and then make the appropriate adjustements.  I then rebuild the old breaker plate with new parts if the unit is still good and does not have any slop.

 

Just a thought to check.  ALso as mentioned before could also be the bearing inthe dizzy that is worn.

 

Rich HArtung

Desoto1939@aol.com

hey Rich… Thanks for the suggestion on the breaker plate… Will check this further when I remove the distributor tomorrow. Ran out of time today. Like your way of working though ... something I'll take moving forward.

[48ratrod]

okay and update on what I believe the problem is… Today I tested the vacuum advance with a vacuum pump-found it wasn't holding any pressure at all… Seems to be a good explanation - Going to have to find me one - SUGGESTIONS on where to look??  None of the local sources here seem to have one -

Re the plugs ... changed them out when was initially getting it going after being in storage ... those were champion - seemed ok and didn't have any complaints - ones I put in now though are Autolite

thanks everyone for your help and assistance so far-much appreciated!

Edited August 30, 2014 by 48ratrod

[Don Coatney]

Air cleaner photo?

 

The vacuum advance is in place as a fuel economizer. It adjusts the amount of timing advance based on engine vacuum to maximize fuel economy. It will not create sooty plugs and your engine will run without it just not as efficiently. There is a company in Texas who sells/rebuilds vacuum advance units.

 

Terrill Machine, Inc.
Engine Parts For Antique Cars
100 County Road 454
De Leon, Texas 76444
Phone: (254) 893-2610
Fax: (254) 893-4841
E-mail: terrillmachine@yahoo.com

[48ratrod]

Don - Thanks for the clarification and the info. Good to know but obviously not the cause of my problems then.

Re the photo of the air cleaner - I had posted them yesterday back previously in the thread - I guess for ease should have just posted in sequence. Here you go anyways.

[Don Coatney]

The air cleaner is your problem. How does air enter the carburetor with the lid in place? Suggest you use a different lid that allows air to enter the filter such as I have pictured below. No air flow is the same as running with the choke closed. This will cause sooty dirty spark plugs and the engine will not run.

 

[48ratrod]

Ok ... thanks - more good knowledge going forward ... will work to address that as I'm sure that's had some effect.

But trying to reconcile this in my pea brain - I did buy it that way and ran it for 5 years - not to mention the guy before me. Just can't see how all of a sudden I'm having these problems because of an air cleaner - it was smooth in acceleration with good power previously.

When the lid is off - I'm having the same problem -

idles great - apply throttle and it gets all rough.

[John Reddie]

Check also for a possible exhaust restriction. A clogged muffler, kinked pipe or a heat riser stuck in the closed position could produce the symptoms you are experiencing.

John R

[Don Coatney]

The paper element you pictured looks new. Was it recently replaced possibly with one not as tall as the old one? Clean/replace your spark plugs and try running the engine with the top of the air cleaner removed.