1925 Won't Start

[JayG]

I've been playing with this for a week now.  Looking for some help.  My 25 roadster won't start.  I've been through the carb a number of times.  Reset the fuel meter pin according to instructions for resetting the arm.  Checked spark at coil and plugs.  Went so far as to get a new condenser and 12 volt coil.  Set the timing per the manual. Pulled the vacuum tank apart, checked that all was clean and working and resealed the gaskets.  Seems to be pulling gas as I added a fuel filter and it filled up.

 

It is trying to fire but seems like it's not pulling gas into the cylinders.  The plugs are not wet and don't smell of gas.  The intake on top of the carb gets cold and after a while gas will drip from the air intake.   It just seems like it's not pulling the gas into the cylinders.  This was running last week but now won't even start.

 

I'm open to any suggestions as I've exhausted all of my troubleshooting ideas.

 

 

[22touring]

Is there fuel in the vacuum tank and is the carburetor bowl full?

[Minibago]

Remove the plugs

Drop a tea spoon of fuel in each cylinder

replace plugs

If it starts it is fuel fuel

If it does not it is electrical

[JayG]

I primed the vacuum tank and the carb bowl is full. 

[MikeC5]

You verified spark, so I'm leaning toward a fuel problem.  It sound as though fuel supply is making it to fuel bowl on carb, so it should at least run on that and what you put into the vacuum tank (even if VT isn't working it should run for a few minutes).  Plugs are dry, so it's not flooding...  Hmmm.  Could something have crawled into the intake and is now plugging the intake path in the head?

[Mark Gregush]

Have you done a compression check?

[JayG]

It's a brand new engine.  Was started initially when I got it back from the machine shop and again last week.  Now nothing just some faint pops.  I did the thumb check and each cylinder has compression.  

[JayG]

I just checked and am getting 50 lbs

[JayG]

Mike. I pulled the carb again.  Nothing in the engine passage. Lots of gas that I absorbed with a rag.  Worth a look.  Now back to the carb I guess

[JayG]

I shot some starting fluid in while the carb is off and it liked that. I guess the carb is the problem.   

[Mark Gregush]

35 minutes ago, JayG said:

I just checked and am getting 50 lbs

50 seems a bit low for a rebuilt engine. My really worn out 1920 does better than that. Wonder if the valve gap is just a smidge tight and valves closing but not quite sealing? But at 50 should run. 

How about your battery? Is it up to snuff? Could be enough to crank the engine over but with all the drag of a rebuilt engine does not have enough left to fire the engine after cranking for a while. Even if it is a new battery they sometimes are bad off the shelf. Went through that with a friends Model T. 

[22touring]

Maybe the carb's air valve ("A" in the factory diagram) became detached from "B", the valve seat. I believe they were originally swaged together, and have been known to suddenly separate.

[JayG]

That’s not the case.  The air valve is not able to be lifted out. It’s popping a little more than it was and maybe Mark is on the right track with the battery.  

[Pete K.]

Anyway possible your exhaust is plugged?

[JayG]

Thanks Pete.  Exhaust is brand new.  And clear.  No varmints living in it.  

[MikeC5]

Do you have a fuel filter in the line from tank?  If not, it could be some crud has gotten into carb.  I installed a filter in the line, accessible with rear floorboard removed.  It should crank at around 60 rpm (one rev per second).  When I first got my car, the stater/gen wasn't working, but I was able to  hand crank it with a battery hooked up direct to coil (and it has 50 psi compression).  So if everything else is right, except it's cranking too slow, see if you can hand crank to get it going.

[JayG]

I do have a filter installed.  The tank was cleaned and new fuel lines run. I think it’s a slow crank issue too.  

[Mark Gregush]

On 5/24/2024 at 5:09 PM, JayG said:

That’s not the case.  The air valve is not able to be lifted out. It’s popping a little more than it was and maybe Mark is on the right track with the battery.  

There was a running issue just recently, where the needle end had separated from the base or shaft and was causing all kinds of running issues. While more than likely not what is going on here, it does happen, but that would be a carb flood running very rich issue not a non-start. 

[BlueDevil]

My newly rebuilt Chrysler 72 engine wouldn't start and it ended up being a vacuum leak which sucked in air between the carb and the block so the fuel never got to the cylinders.

[JayG]

Mark.  The needle is intact. I’ve had the carb apart too many times looking for a cause.    I’ll keep checking for vacuum leaks and work on the slow crank issue.