jps

question about spark plugs and engine cranking

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For the past month or so I have had no luck starting my engine.  I verified I have spark to all 6 cylinders, and just last year I put in a rebuilt 1928 carburetor that was set up and adjusted for me by a 27-28-29 Buick expert.  Each time I try to start (probably about 10 times in the past 4-5 weeks) I crank for 6 or 7 times, each crank lasting a few seconds with pauses in between.  I have also tried blasts of starting fluid.  After 6 or 7 cranks I see fuel dripping out of the air cleaner.  However, when I tried this again today (including use of starting fluid) and  ended with the same no start, I immediately removed and checked 2 spark plugs and they both were completely dry.  Shouldn't they have been at least a little wet after 6-7 cranks with fuel obviously getting to the carburetor?  I sniffed each plug and could only get a faint fuel smell on each one - I expected to have more obvious of a fuel smell to them.

 

Thanks

 

John

 

 

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John, internal combustion engines require four things to run. Fuel, ignition, compression, and timing. Any one of those  is gone and you will not run. Start with the basics. Do you have adequate compression? Should be 50 lbs or more. If you have been using starting fluid we can assume there is fuel. Check if you have a hot spark while cranking. Pull the coil wire out of the distributor cap and hold it about 3/8” from a ground and have a helper crank the engine. If you have a weak or no spark it is likely that your starter is pulling the battery voltage down too low for the ignition to work properly. This could be due to a low performing battery or more likely having battery cables that are too small, and bad connections on them. Six volt cars need big cables. If you have good compression, hot spark, and fuel, only incorrect timing will keep it from running. If you can’t get it to run send me a PM and I will work through it with you. I love these Buicks. Here’s a pic of mine.

98C13246-0959-457F-AEAA-8B3DC682087F.jpeg

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When you check compression, you aren't really checking compression. You are checking the rings and valves, and you are checking them to check the intake vacuum for each cylinder. Fuel won't get into the cylinder without vacuum. Your spark plugs are dry which means fuel is not being sucked into the cylinders during the intake (vacuum) stroke.

 

But if the compression is good that means the rings and valves are good, and if the rings and valves are good, the intake vacuum is good. So check the compression.

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If you have a Marvel carb, it is critical that the fuel level in the bowl be very close to the idle jet top.  About 1/16" is needed.  The lower the fuel level, the more vacuum you need to draw the fuel up to mix with the incoming air.  I had neglected this on my 1917 D45 and it was hard to start.  I marked the inside of the bowl to indicate the idle jet height.  I set the float to allow the level to be just below this mark.  Starting problem solved.

 

Bob Engle

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I suggest you verify timing.  Retard spark, bring #1 piston to top dead center, and verify that the rotor is lined up with #1 spark plug to fire.

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13 hours ago, jps said:

For the past month or so I have had no luck starting my engine.  I verified I have spark to all 6 cylinders, and just last year I put in a rebuilt 1928 carburetor that was set up and adjusted for me by a 27-28-29 Buick expert.  Each time I try to start (probably about 10 times in the past 4-5 weeks) I crank for 6 or 7 times, each crank lasting a few seconds with pauses in between.  I have also tried blasts of starting fluid.  After 6 or 7 cranks I see fuel dripping out of the air cleaner.  However, when I tried this again today (including use of starting fluid) and  ended with the same no start, I immediately removed and checked 2 spark plugs and they both were completely dry.  Shouldn't they have been at least a little wet after 6-7 cranks with fuel obviously getting to the carburetor?  I sniffed each plug and could only get a faint fuel smell on each one - I expected to have more obvious of a fuel smell to them.

 

Thanks

 

John

 

 

 

Has any work been done on the engine?  The camshaft to crankshaft orientation might be off.

 

The next thing is one of the timing gears might be damaged/ stripped.  Take the cover off the engine and see if the rocker arms are moving when cranking the engine over.  If they are not moving you now know the problem.  Bad timing gears.

 

Keep us posted on your progress.

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Thanks to all so far that have offered suggestions and insight.  I did not originally list all of the things I have done recently, so here is a summary:

 

1) compression on all cylinders is 55-60 psi except #3, which is 40-45 psi

2) Battery is pretty new (2 years old) and I just charged it on Sunday before I tried starting again

3) Spark plus, wires, points, condenser, and distributor cap are all relatively new (3 years or less) with less than 1000 miles on any of them.

4) I checked spark on the main high voltage feeder to the distributor, and also to each individual plug and there was a spark in each case.  I am not convinced the spark was great, but it was present.

5) A few times in the last few years when the car doesn't want to start I have checked the plugs after trying to crank for awhile and I have never seen them wet yet.

6) I have tried starting fluid 3 - 4 times lately and have not been successful any of those times.

7) In the last month I have timed the ignition per the service manual twice (fully advance spark control on steering wheel, watch #6 valve action as you crank engine until flywheel is at the 17 degree mark at the view port, ensure rotor is pointing at plug #1, adjust distributor contacts to just barely open)

 

 

Also, last year I put in a new mechanical fuel pump (the one in the car when I bought it was not connected), switched over to a 1928 carburetor to avoid the problems with pot metal on the '29 bowl, and added in a hard line vibration loop between the pump and carburetor.  I also re-wired and re-plumbed the electric fuel pump that the previous owner added so that it would not operate unless I switched it on - it previously was always on when the ignition was on.  I try not to use it anymore but have it available as a backup if necessary.

 

The idea about keeping the fuel in the bowl at the right height might be a good place to start - I did have that problem somewhat with the original carburetor a few years ago before replacing it.

 

Fuel is certainly getting into the carb body (because it eventually drips out of the air cleaner after cranking awhile), but since the plugs always seem dry I am thinking that fuel isn't getting pulled up into the cylinders.  That seems to agree with the starting fluid not helping because I spray a burst into the air cleaner, so it would still have to get pulled up into the cylinders.  If that is the problem, I am not sure what the root cause is, although a few ideas were mentioned in your answers.

 

Thanks to all for your ideas, thoughts, and suggestions.

 

John

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8 minutes ago, jps said:

Thanks to all so far that have offered suggestions and insight.  I did not originally list all of the things I have done recently, so here is a summary:

 

1) compression on all cylinders is 55-60 psi except #3, which is 40-45 psi

2) Battery is pretty new (2 years old) and I just charged it on Sunday before I tried starting again

3) Spark plus, wires, points, condenser, and distributor cap are all relatively new (3 years or less) with less than 1000 miles on any of them.

4) I checked spark on the main high voltage feeder to the distributor, and also to each individual plug and there was a spark in each case.  I am not convinced the spark was great, but it was present.

5) A few times in the last few years when the car doesn't want to start I have checked the plugs after trying to crank for awhile and I have never seen them wet yet.

6) I have tried starting fluid 3 - 4 times lately and have not been successful any of those times.

7) In the last month I have timed the ignition per the service manual twice (fully advance spark control on steering wheel, watch #6 valve action as you crank engine until flywheel is at the 17 degree mark at the view port, ensure rotor is pointing at plug #1, adjust distributor contacts to just barely open)

 

 

Also, last year I put in a new mechanical fuel pump (the one in the car when I bought it was not connected), switched over to a 1928 carburetor to avoid the problems with pot metal on the '29 bowl, and added in a hard line vibration loop between the pump and carburetor.  I also re-wired and re-plumbed the electric fuel pump that the previous owner added so that it would not operate unless I switched it on - it previously was always on when the ignition was on.  I try not to use it anymore but have it available as a backup if necessary.

 

The idea about keeping the fuel in the bowl at the right height might be a good place to start - I did have that problem somewhat with the original carburetor a few years ago before replacing it.

 

Fuel is certainly getting into the carb body (because it eventually drips out of the air cleaner after cranking awhile), but since the plugs always seem dry I am thinking that fuel isn't getting pulled up into the cylinders.  That seems to agree with the starting fluid not helping because I spray a burst into the air cleaner, so it would still have to get pulled up into the cylinders.  If that is the problem, I am not sure what the root cause is, although a few ideas were mentioned in your answers.

 

Thanks to all for your ideas, thoughts, and suggestions.

 

John

 

 

Check for leaky intake manifold. If the compression is good and gas isn't getting into the cylinders, maybe air is leaking in at the intake manifold. 

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Hi Larry - I just verified that when I hand crank the engine I can see all 12 valves move in sequence, so I think the rocker arms must be OK.  Very good suggestion to check them, though.

 

I also agree with Morgan's idea to check for an intake manifold leak.  That thought crossed my mind earlier but I don't yet have a method to tell if it is leaking.

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John,

 

Most auto parts stores sell a neat gadget that enables you to get a rough idea of the spark voltage. It goes between the plug wire and ground (or the coil HV output and ground). You can quickly see what the spark quality is. Not as good as an oscope but much cheaper. Advice - adjust the screw when not cranking (or running) the engine or you will get gigged.

 

https://www.amazon.com/OriGlam-Adjustable-Ignition-Circuit-Diagnostic/dp/B06X9RC3PF?SubscriptionId=AKIAILSHYYTFIVPWUY6Q&tag=duckduckgo-ffhp-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B06X9RC3PF

 

Cheers, Dave

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Another thing, if you are worried about the starting fluid getting to the cylinders try taking out the plugs and shooting some (not a lot!) in there and replacing. It should at least fire.

 

Cheers, Dave

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If fuel is dripping down the air filter, I'm assuming its a updraft carb,  I wouldn't worry about the carb yet.

You need to confirm your timing and re-check all you ignition parts, ie points, condensor, coil, spark leads/plugs(what is the colour), wiring to the distributor, etc. 

 

Does it fire at all?

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No start for the last month or so but running okay prior to that? Assuming so what, if any, work have you done since it was running? You've indicated that you've confirmed that you have compression, spark and fuel (at least starting fluid) as well as valve actuation. That pretty well leaves timing as the culprit I'd say. Good luck solving the mystery...

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Use a modern timing light and power it using any 12 volt source (jumper wires from a car battery or use an alarm battery). Clip it on #1, advance the timing at the steering wheel, and you should see the flashes on the 17 mark on the flywheel.   Vacuum gauges are around $20 on Amazon.  It would be interesting to know what you get while cranking.  Also be sure to hold the throttle wide open when cranking and using starting fluid if you really want to pull it into the engine and not just the carburetor.  

 

 Hugh

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During the past month only? Has it been cold the past month in Minneapolis?

 

My car starts without the choke in the summer. Never touch the choke. In the past month I have had to use the choke to get it started. It was 30 the other morning, no start at all, until I used the choke, then it started right up.

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Update:

 

I bought a self-powered timing light and cranked the engine.  The timing looks correct.  However, the bulb in the timing light only flashes about 1/2 of the time that it should, so I think the voltage to the coil is weak.

 

While checking voltages I found that I am losing almost 1 V right off the bat between the battery and the ignition coil with the ignition switch on and nothing else happening.  A lot of the wire in the car looks original and has breaks in the insulation in several spots, so I am re-wiring the complete circuit from the starter to the ignition switch and back to the coil with new wire.  I also will check the ignition switch resistance.  It looks to me like there isn't enough voltage getting to the coils to reliably fire the plugs.

 

Once the rest of my wire arrives I will finish and see if that takes care of the problem.  I probably will rewire a few other circuits too.  I am hoping that this has been the main problem all along - the car has been hard to start ever since I bought it in 2014.  

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Are those numbers normal for the compression on these engines? That's not too far off from mine (1917 "light 6")

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Is your spark at the plug a good blue spark or an yellowish orange.   Blue spark is good,  the yellowish orange means your coil is about shot.   I generally squirt about 3 -5 pumps of motor oil into the cylinder to help with compression and to suck in the fuel for the first starts.      Works for me

 

Tom

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Otto Cycle: It is my understanding that good and normal compression numbers for my engine, which is different than yours, should be 60 - 65 psi, and just as important, all cylinders should be within about 5% of one another.  My #3 is too low at 40-45 psi, but I don't think that will really affect starting.  It should negatively affect efficiency a little and probably make the engine run a little less smoothly.  I plan to leave that cylinder "as is" for now.  If you get 60 psi on your engine I think you are good.

 

Tom: The spark color at the plugs is not consistent, although it is blue most of the time on most of the plugs.

 

John

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JPS,  one volt on a six volt system is a significant.  I have, in the past,  used a jumper wire from the battery directly to the coil for testing purposes. Might start easier. Or not. Would, at least, let one know if  the voltage drop is the culprit.

 

  Ben

 

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It seems that it should cough and try to start.

 

Here Are my suggestions:

 

Check the routing of the plug wires from the distributor cap to each plug. You replaced the distributor cap so double check.

 

When timing it if you pass the timing mark, do not back up the flywheel to set on it.  Go around again.  That should eliminate any backlash from a worn distributor gear.

 

Re time it 180 degrees from where you are now.

 

Also run a piece of 600 sand paper through the points to break any glaze that may be on them.

 

 

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