1928 Standard Roadster - Runnability Problem

[TFB3]

I'm trying to think my way through a runnability issue with my 1928 Standard that I bought recently.  The car starts nicely, idles nicely and runs well until it warms up. After 8-10 minutes of driving, the weirdness begins. I can feel power surge and cut, surge and cut, all very fast as if it's sputtering. It's subtle; I doubt a passenger would notice it unless I pointed it out, but it's definitely not right. Then when I get it home and let it idle, it sounds like it's going to shut down at any moment, but it always continues to run. It runs, then "almost" dies, then continues running, then drops to near zero again, etc..... If I raise the throttle, it's no longer in danger of dying, but there's a definite skip that can be heard. Just as an FYI, if I shut it down and start it again, it fires immediately and resumes all this weirdness.  

 

So here's what I've done so far:

 

1. I think the carburetor is alright. I've adjusted the fuel/air such that more air will cause backfire and less air will starve the car at speeds over 15 mph. My vacuum is steady at about 16 lbs.
2. I replaced spark plugs, cap, rotor, coil, and wires. New points and condenser won't arrive for another few days, so I cleaned the current points and set them to 0.018 gap. 
3. I adjusted the spark advance lever to get full movement back and forth at the distributor, but it has only a small effect on engine behavior when I slide the lever either way. 

 

Here are my suspicions:

 

1. I wonder if new points will help. Most of what I've read suggests that bad points and condenser cause starting issues, but they wouldn't really change runnability when cold vs hot. 
2. I'm wondering if increasing both fuel and air might help, but I'm not sure. It wouldn't make sense unless a hot engine would require more fuel and air volume anyway. ??
3. I wonder if I have the "holes in intake tube" issue I've read about, but I'm not sure what the symptoms of this problem would be. FYI, there's no change in runnability when I slide the "heat" lever up or down. Besides, I'd think exhaust-into-intake problem would be just as bad when the engine cold and when it's hot. 
4. I doubt it's the culprit, but the original vacuum fuel system wasn't working properly, so the previous owner installed an electric fuel pump. I could see how inadequate fuel pressure could inhibit high RPMs, but it wouldn't explain the trouble at idle. Nor would it explain the difference in runnability when the engine is cold vs hot. 
5. Could out-of-adjustment valves cause this kind of behavior? <gulp>

 

If anyone has any ideas, I'd be happy to get a few clues to follow. And if anyone might have some good explanations of what to look for (symptoms) of bad points, fuel/air, valves, exhaust tube leaking.... I'd be happy for the education. 

 

thanks!

 

Tom in NH

1928 Buick Standard Six Roadster

[JFranklin]

What happens to the different components when heated will give you the best answers. Could it be an iffy coil? or manifold warp causing an intake leak? Condensers fail differently when warm. Fuel lines too close to exhaust systems causes trouble when hot. 

[edinmass]

If it’s electrical coil and condenser come to mind. And electric fuel pump powered on through the ignition switch will under volt the coil after a short while also. Don’t jump around or guess. Diagnose it……one item at a time and eliminate possibility’s to you get to the problem. Coil would be my first suspicion IF and that’s a BIG IF all other items are in 100 percent operating condition. In a hundred year old car……everything must be proved correct and operational at 100 percent………too many people trust what others have told them, or what other people have passed as “ok”. If I was working on the car, I would listen to your complaint, road test, and start from zero on figuring out what is wrong. One thing that is difficult to explain is forty years of diagnosing running problems and figuring out if it’s mechanical, electrical (ignition), or fuel. Not having a well equipped shop is also a major issue for most shady tree mechanics. 

[raydurr]

One of the most overlooked causes of low power and erratic running on the Buicks is the heat riser. The sheet metal tube can have a pinhole in it and driveability ad tunability goes out the window.

Search the forum. There are dozens of stories addressing this.

[TFB3]

A few more clues here: A few of you mentioned the possibility that the coil might be the problem. But I had already replaced the coil. The original and the new one behave exactly the same, so it's probably not the culprit. Ed also mentioned that the coil could possibly brown-out the voltage if it's been wired through the ignition switch, and yes, mine has been. So I rewired the fuel pump to remove it from the ignition switch circuit and wired it directly to the power brick up under the dash on the firewall. 

Drumroll....... the results were exactly as before. It starts and runs nicely until it warms up, then it starts to stumble. I takes a little less than 3 miles, but it's definitely still there. Tuesday I'm expecting new points and condenser to arrive, so I'll install those and see if anything changes. 

[TFB3]

3 hours ago, edinmass said:

Full time used car mechanic. Pre War only.

I can fix ANYTHING- how much time and money do you have?

If it’s not pre war, I don’t know anything about it.

Ed, I spotted your signature line. My antique mechanic has retired, and I'm not much more than a tinkerer, so I'm in need of a new one with exactly your kind of expertise. Are you looking for new clients? 

[TFB3]

4 hours ago, JFranklin said:

What happens to the different components when heated will give you the best answers. Could it be an iffy coil? or manifold warp causing an intake leak? Condensers fail differently when warm. Fuel lines too close to exhaust systems causes trouble when hot. 

Thanks. I had a look at the fuel lines and they seemed alright; the part going into the carburetor was cool to the touch. I then put my hand on the vacuum fuel canister and it was pretty hot, so I thought I'd found something..... until I touched the horn and found it to be exactly the same temperature. LOL  Obviously, being in the engine bay comes with the consequence of being a bit on the hot side. LOL  

 

I then did a bit of investigating to see if maybe I had a warped intake manifold or carburetor plate. With the car running, I sprayed a bit of brake cleaner on the place where the intake meets the engine... no effect. I did the same with each carburetor-to-manifold connection... no effect. (that is until I got too close to the air-cleaner/ flame-arrestor... that, understandably caused a bit of an engine bog as it tried to digest the cleaning fluid). 

 

Thanks for the suggestions. Tom

[TFB3]

3 hours ago, raydurr said:

One of the most overlooked causes of low power and erratic running on the Buicks is the heat riser. The sheet metal tube can have a pinhole in it and driveability ad tunability goes out the window.

Search the forum. There are dozens of stories addressing this.

Thanks, yes, I've read about this, but I'm still not sure what symptoms it causes or what to look for to indicate this might be a problem. Does it effect runnability both cold and hot? Or just hot, like my situation? I'll keep scanning the articles to see if I can find more about it. 

[edinmass]

Disconnect the condenser and try running it for half an hour. See if it still does the same thing. 

[edinmass]

30 minutes ago, TFB3 said:

Ed, I spotted your signature line. My antique mechanic has retired, and I'm not much more than a tinkerer, so I'm in need of a new one with exactly your kind of expertise. Are you looking for new clients? 

I only work on prewar cars if they are local. If you’re in the palm beaches, PM me. Happy to help you out here the best I can. 

[TFB3]

35 minutes ago, edinmass said:

I only work on prewar cars if they are local. If you’re in the palm beaches, PM me. Happy to help you out here the best I can. 

Hi Ed, I thought you might have been in Springfield MA, which is somewhat local (flatbed distance anyway). I'm in southern NH, just over the MA border. Maybe one day I'll move down the FL, but I'm up here for now. Thanks!

[edinmass]

Moved south six years ago…..have a summer place in Western Mass…….but I am only there a few days a year.

[TFB3]

3 hours ago, edinmass said:

Moved south six years ago…..have a summer place in Western Mass…….but I am only there a few days a year.

Ah, it's a good move. My brother just moved to FL too.  Any recommendations for a pre-war mechanic up this way?  I'm going to need someone to rely on, because I like this car; it's going to be with me for a long time. 

 

As a last test for the night, I removed a condenser that was attached to the positive lead on the coil. Not sure why it was there, I've never seen one in such a place before, but I removed it to see if it had any effect. During another 6 mile test drive, it did seem to run a bit better. The skipping feeling was still there, but it seemed to be considerably less. The hot idle was just as bad as before though. Maybe I just had a lucky run??  Or maybe we're on to something??

 

Next, I'll see if removing the condenser in the distributor has any effect. And then, when my new condenser and points arrive Tuesday, I'll see if those have any effect. 

 

Thanks as always!  I'm looking forward to laughing about this when it's all figured out. 

[hidden_hunter]

Now you’ve had it running it for a bit after cleaning things up like the points, have you looked to see if there is any abnormal wearing on them (or the distributor track)?

 

what do your plugs look like?

[EmTee]

Also check the condition of the ground wire on the breaker plate.  If the connections are iffy, heat increases resistance.

[michealbernal]

Marvel carburetors of this vintage are critical on settings.  The venturi on them is made of pot metal which ''grows' over time and this can cause all kinds of problems.  When I bought my 1928 Standard the carburetor settings were totally wrong.  I bought Bobs Automobilias book on Marvel Carburetors and rebuilt mine using the book as a guide.  My car runs perfectly now.  

[Oldtech]

You can't run it with the distributor condenser out. It probably won't even start, but if it does you will fry the points.

[TFB3]

On 5/16/2022 at 8:30 AM, EmTee said:

Also check the condition of the ground wire on the breaker plate.  If the connections are iffy, heat increases resistance.

Thanks. I've verified good ground to the distributor. 

[TFB3]

17 hours ago, Oldtech said:

You can't run it with the distributor condenser out. It probably won't even start, but if it does you will fry the points.

Good to know. You caught me before I tried it. The new points and condenser are in and there wasn't much change. 

[TFB3]

On 5/16/2022 at 10:28 AM, michealbernal said:

Marvel carburetors of this vintage are critical on settings.  The venturi on them is made of pot metal which ''grows' over time and this can cause all kinds of problems.  When I bought my 1928 Standard the carburetor settings were totally wrong.  I bought Bobs Automobilia's book on Marvel Carburetors and rebuilt mine using the book as a guide.  My car runs perfectly now.  

You may be onto something. Now that it's got new points, I've replaced everything in the ignition system that I can think of.... coil, points, condenser, rotor, cap, wires and plugs and it's not really any better. Interestingly, I pulled a plug wire to see what color the spark would be and it's perfect; bright bluish-white and it jumped almost an inch. (it packs a good whack too!) Seems to me the spark is good. 

 

On my test drive a few minutes ago, it was sputtering, then refused to go above 10mph. I pulled over a number of times to play with the fuel and air knobs and was able to see big changes, both bad and good..... after a few attempts was able to get the engine running well enough to get home. Here's another interesting clue:  The engine idles alright, but when I'm driving, it really jerks back and forth as if I'm hitting and releasing the throttle rapidly...... but, if I just hold the throttle button to the floor, it runs smoothly without all the back and forth jerking. So I'm thinking maybe the carburetor could be worth looking into???  

 

I'm also wondering if the fact that the engine runs smoother with the "pedal on the floor" is an indication that the intake tube has pin holes. Maybe the wide open throttle helps overcome an exhaust gas leak, where part-throttle can't? Then again, it could just be rotational inertia smoothing out the skipping underneath. Can anyone describe the symptoms of the pin hole problem? I haven't been able to find a description of what to look for.... just that it causes problems. No idea what problems though. 

 

I just bought the Marvell book from Bob's, along with their vacuum fuel tank repair kit. I just wish I had some experience to draw on with this process or even better, a good mechanic to bring the car to.... I'm not the guy I'd hire to troubleshoot this stuff. LOL

[dibarlaw]

TFB3

Some of what you are describing is characteristic of a leaky riser tube. I am sure there are some other factors.

 Check for obstructions on the gas cap. Also, if your electric fuel pump has rubber hose connections there may be a leak. Mine did! That is when I rebuilt my vacuum tank and have had no issues since.

[32buick67]

Tom,

If you willing to do a little deeper troubleshooting on the heat riser and T-3 Marvel carb, I have some suggestions...and at some point I recommend inspecting the carb system since its known originally as a high maintenance design - it works fairly well for original equipment when maintained, but if one or two elements are off by just a bit, the engine performance may quickly vaporize.

• Follow the Marvel manual for your car.
• Follow the Marvel manual "Carburetion in relation to service - how to overhaul a Marvel carbureter Booklet 87".
• Heat riser - simple quick eval - check heat riser leaks with a shop vacuum on the exhaust diverter valve cross pipe to see if the carb air horn is drawing any air.  Note, this will involve removing the exhaust diverter valve.
• Caution - the large brass screw is NOT an air fuel ratio mixture screw, and it is NOT an idle adjustment screw.  Marvel labeled this as the "air adjustment screw" which is not something which easily translates into modern carburation terms based on the various manuals and documents that Marvel made to describe its function.
• The compound spring 24-115 has multiple spring rates across the entire engine performance range for idle and power function.  If you have a straight spring inside the screw housing, it may not function well for your engine.  Check out Carbking on this forum for an accurate modern rebuild kit and more info.
• The air spring inside the air valve screw must be exactly 1.5" in length and be of the compound type with a number of closed coils in the center (resembles a barrel).
• Remove the carb and inspect items like the 111-3 venturi spacer block quality for perfectly concentric venturi ID, no cracks or swelling, free tail clearance for the air valve.  Search this forum for venturi problems and solutions.
• Ensure correct low speed nozzle elevation, float elevation, float valve seating, air valve free play, air valve seating, high speed jet wall clearance, low speed and high speed jet part numbers and orifice IDs.

Not saying the carb is the culprit to all of your struggles, but its one of the critical elements and should looked at, deeply, at some point in the future to ensure a fun and reliable driving season with decent mpg.

If you have already proven the basics like ignition, fuel, compression, etc., then your carb setup might be one of the last elements to investigate, and in the case of Marvel designs, its quite demanding of your time to RTS.

 

I have spent a ridiculous amount of time and fuel over the last few months, with the help of other expertise, to build, rebuild, test, tune, intentionally disrupt and re-establish correct settings, redesign and prove procedures to ensure correct setup of a select group of Buick Marvel carbs.  I am happy to report very good results, which has yielded relevant practical knowledge and performance modeling.  On the flipside, some folks have unfortunately tried to modify their Marvel carbs to make them perform, but they actually harmed them by installing non-OEM jets, applying obscure parts and modifying original parts which harmed their efforts to achieve their goals of performance and mpg. 

 

Is one of these your carb?

 

Or 10-608 or 10-610?

 

PM me to chat more details, too much to type on this topic...

Mario

 

[TFB3]

56 minutes ago, dibarlaw said:

TFB3

Some of what you are describing is characteristic of a leaky riser tube. I am sure there are some other factors.

 Check for obstructions on the gas cap. Also, if your electric fuel pump has rubber hose connections there may be a leak. Mine did! That is when I rebuilt my vacuum tank and have had no issues since.

Thanks Larry, A little more reading and I found a few write ups indicating that the pin-hole problem causes loss of vacuum. From what I've read, 18-19 lbs of vacuum is ideal and I'm pulling around 16 lbs with a regular blip down to 15.5. So it's not ideal, but I suppose it's not all that bad either. 

When I put in the new points, things seemed to get a bit worse. They're gapped properly at 0.018, but I wonder if I effected timing when I installed them. The car now idles quite a bit faster than before and it now prefers the advance lever at full advance. Before it didn't really make much difference where that lever was. 

 

I think I'll be adding a timing check to my to-do list along with the vacuum tank rebuild. 

[TFB3]

53 minutes ago, 32buick67 said:

Is one of these your carb?

Or 10-608 or 10-610?

Hi Mario, Thanks for the details.  If there's a reputable rebuild service, I'd definitely consider sending my carburetor to them and let a professional deal with it.

 

This car had a total restoration back in 1996 and hasn't seen an actual road since (until I bought it that is); just on and off trailers to shows. My intention is to drive it to local shows, but all the time sitting with nothing more than 100 yard drives took it's toll. It's definitely in need of some fine tuning. 

 

That carburetor appears to be a 10-103. 

[BuickTom87]

That’s the same carburetor on my 29, there’s a specialist for these cars in Wisconsin.  He can help you over the phone with it . He helped me with my 29 Buick . He’s a specialist for 27 28 29 and his name is listed in the Buick bugle . These carburetors are tricky… I really don’t recommend having this guy rebuild your carburetor though he takes too long to do it. 
 

if you want message me and I’ll send you what ever information and knowledge I have for these carburetors. I’ve learned a lot in the last year, I even got brand new rebuild kits for these  carbs because they are hard to come by.

[BuickTom87]

The fuel line going to your carb, do you have a looop or is it a straight line? I’ve also heard you need a loop for it . I had a straight line on mine and always had issues , then had it rebuilt and had the fuel line looped and now it runs fine 

[Terry Wiegand]

TFB3,

I have been following this thread rather closely since I am no stranger to a poorly running Buick 6-Cylinder engine.  On the posting that you had Sunday you said that you removed the condenser from the + post on the coil.  Then you stated that you were going to remove the condenser in the distributor - HUH?  As far as I know these engines have only one condenser in the ignition system.  With regard to the coil, the electrical power comes IN on the positive post and exits on the negative post.  The condenser is fastened to the coil's negative post.  I am enclosing a photo of the Onan condenser that I am running on my 1916 D-45.  They are engineered for high heat applications and have a longer pigtail lead than a standard unit.  I will give you the advice that was given to me when I was searching for the problem(s) with my 1920's engine.  You have to check each and every piece in the system and be able to eliminate it as the problem or it gets replaced.  Check the distributor cap for any possible cracks.  Check each plug wire for continuity.  Just because you have a new coil and condenser does not mean that they are good.  It has happened that new ones can be bad.  Check that your connections are good and solid.  Someone mentioned earlier to check the distributor head thoroughly - excellent advice.  If you can eliminate the electrical side as a problem source, then you are one step closer to solving your problem.  I know from personal experience that electrical issues can mimic fuel system issues.  These heat riser tubes can and do cause issues that will have a person doubting their sanity.  A good compression test is always a good idea also.  Patience and perseverance will always be at the top of any thing that you do.  One fellow on these forums has told us that "Old Cars Ain't Easy".  No truer words were ever spoken.  I wish you the best in locating what is ailing your engine.

 

Terry Wiegand

South Hutchinson, Kansas

AACA Life Member #947918

[Oldtech]

Condenser on the + side of distributor is normally for radio interference.  Not sure why that car would have one. it doesn't effect the ignition system.

[Dave39MD]

When it is running bad does pulling out the choke a little bit, say 1/3, help smooth it out?

 

Dave

[edinmass]

On 5/17/2022 at 12:51 AM, Oldtech said:

You can't run it with the distributor condenser out. It probably won't even start, but if it does you will fry the points.

 

Running it without it won't fry the points. It's a good way to see if there is a problem with the condenser. I have driven a few hundred miles without one one when I had no choice, and the points were fine. 

[edinmass]

 Tom, if you like you can send me your distributor next week, and I will put it on my Sun tester and check it out. New coils are known to have a high failure rate. I have test equipment for that also. Just send it to me flat rate USPS, with a return pre paid label, I will check it out and set it up no charge......I have done it dozens of times for members here..........below is a video of a 1940's coil tester.........with a 1929 Rolls Royce P1 coil.

 

 

 

 

Edited May 19, 2022 by edinmass (see edit history)

[raydurr]

One other thing that causes power loss after warm up are valves adjusted too tight. I have seen it on a few occasions.

[TFB3]

On 5/19/2022 at 8:26 AM, edinmass said:

Tom, if you like you can send me your distributor next week, and I will put it on my Sun tester and check it out. New coils are known to have a high failure rate. I have test equipment for that also. Just send it to me flat rate USPS, with a return pre paid label, I will check it out and set it up no charge......I have done it dozens of times for members here..........below is a video of a 1940's coil tester.........with a 1929 Rolls Royce P1 coil.

HI Ed, Thanks for offering, I may well take you up on it. That's a really great coil testing tool you've got too. I'm pretty sure the coil in my car is healthy because it throws a bright bluish-white spark and it'll easily jump at least 3/4 of an inch. 

 

 

[TFB3]

Today I tried a few more things and the engine is running much better! The thing that made the most difference was adjusting the timing (again). A few days ago I had set it by-the-book, by watching the valves, finding the "17" mark on the flywheel, gently moving the distributor CCW until the opening-point was reached, etc.... By the book it was correct. But I remembered that my 1954 Lincoln doesn't run well when the timing is set to the original specifications, so maybe the Buick has a similar issue. 

 

Anyway, with the engine running, I just loosened the distributor and moved it ever so slowly back and forth to see where the engine ran best. The sweet spot ended up being about 1/4 inch clockwise from where it had been (measured at the outer circumference of the distributor base just beneath where the cap meets the base). I think that means I retarded it, but I'm really not 100% positive, nor do I have any idea if that's a large adjustment or a small one. I then re-adjusted the fuel and air knobs on the carburetor for best idle. Interestingly, even after achieving a smooth idle, I had to increase the fuel knob several times to get the car not to feel herkie-jerkie and starving under acceleration. I had to do similar with the air knob, but I think I've made some good progress to a better end at this point. 

 

The results:

1. vacuum is up to 19 lbs (was 16 lbs)
2. the herkie-jerky surge-cut-surge-cut-surge-cut behavior is gone
3. the fuel knob is backed out 2.1 turns from fully seated
4. the air knob is backed out 1.5 turns from "flush" with the marker
5. the skipping while driving is drastically less, not entirely gone, but I can usually eliminate it by playing with the spark lever on the steering wheel (it seems to prefer more advance as it heats up)
6. the car idles much better now, just a tiny bit of hunting, but I'm being a bit picky there, it's dramatically better now, I may get a video tomorrow for posting
7. the engine is noticeably less loud during acceleration, I have no idea why this would be, but it used to make more of an exhaust growl under heavy throttle

FUNNY - At one point during all my test driving today, after some very encouraging success, I thought all was for not.... the car suddenly lost all power and would barely maintain speed. When I opened the hood, I discovered that this little lever had fallen off. The PO had wrapped a paperclip around the bracket (clearly visible in this picture) to hold it onto the pivot point instead of simply sliding a cotter pin through the hole. Hmmmm...  I quickly put it back on, this time with a proper cotter pin and the good behavior returned immediately. Can anyone tell me what this is? And maybe what it does? I'm going to guess it's the accelerator pump but I have no idea what the effect would be of having it fall off like this.

 

. 

 

 

Edited May 22, 2022 by TFB3 (see edit history)

[hidden_hunter]

8 hours ago, TFB3 said:

Can anyone tell me what this is? And maybe what it does? I'm going to guess it's the accelerator pump but I have no idea what the effect would be of having it fall off like this.

 

It’s the metering pin

[raydurr]

I call it the high speed jet metering pin. Search Marvel Metering Pin within the forum achives.

[dibarlaw]

Yes, the metering pin is an early version of an accelerator pump.

[TFB3]

Quick Update:  I'm copying this update from another post I just made because it's relevant for this discussion too. 

 

I reduced the idle from 700 to 360 and retarded the timing a bit more. Now for the first time, the spark lever produces a noticeable RPM difference from top to bottom. Using a timing light, I can see that I'm at 22° / 460 rpm at full advance and 0° / 360 rpm at full retard. My vacuum has dropped three pounds to 16 lbs; undoubtedly the result of dropping the idle from the previous 700 rpm.

 

The new lower idle definitely helps get into gear while stopped, but it still protests every so often when hot, so I'll probably try the 2:1 mix of Lucas 80/90 and Oil Stabilizer that everyone talks about. I've also dropped my shift points way down so I'm into 2nd at about 5mph and into 3rd at about 10mph; it's much more cooperative! I do still get the occasional engine burp while underway, but it's only when hot and it seems to go away when I increase the advance to maximum. I can also report that the hot idle now seems stable and smooth. 

 

For someone who's accustomed to listening to modern engines, it's amazing how much more of the mechanical sounds you can clearly hear in an old-fashioned, long stroke engine when it's running at 360 rpm.   I'm definitely making progress. Thanks for all the help. I'm sure I'll have more to report in the coming days.