1940 roadmaster starts, then dies

[Drakeule]

Starts, then cannot rev and dies, Sometimes just limps along at idle, until I attempt to rev. Occasionally backfires. Relined tank, new fuel pump, and rebuilt carb. When I installed all, seemed to run fine for a while, then the conditions I just described.  When I disconnect the fuel line at the carb, pumps plenty of gas. Fresh gas too.

 

I'm not sure what is going on here. I had this problem about 2 weeks ago and thought it had resolved. If gas has some water in it, it shouldn't start right? Too much fuel pressure? (mechanical pump, non variable?)

 

Bad electricals? (I replaced points, condenser, wire plugs rotor and cap.)

 

Any input appreciated!

 

CD

[1937 Buick 66C]

Hello Drakeule,

 

This sure sounds like a carburetor problem, especially since you have been doing work on the fuel system.  On these old Buicks, there really isn't anything electrical that is different between idle and off-idle operation.  If it is idling OK, probably not electrical.  Based on your description, when you open the throttle, the blast of air leans out the mixture and the car dies.  I suspect two probable culprits, or maybe a combination of both:

1. The accelerator pump is not pumping fuel when the throttle is opened.  With the air cleaner removed, peer into the carburetor with a bright flashlight.  When you open the throttle, you should see a distinct squirt of fuel into the throat of the carburetor.  If nothing, or a drip or two, some part of the accelerator pump circuit is not functioning properly or is blocked.  To properly service, you will need to remove the carburetor, then get the pump working properly on your workbench.
2. The main fuel jet has become clogged with some debris.   You may be able to correct this by removing the carb cover and spraying carburetor cleaner into all of the orifices and openings you can see with the cover removed.  If this is not successful, you will need to pull the carb and take it apart and clean blow out all of the orifices. 

 

[Drakeule]

And tonight, when everything cooled off, it started with little trouble. I was able to nurse it back into the garage. Idle OK, off, then started again, no problem!

 

I will check the above accelerator pump issue, then squirt some carb cleaner in, just like Jon said to do. I can also blow it out with compressed air.

 

It does make more sense that it's the carb, but I will check the electrical again just to be sure.

 

If this problem reoccurs, I will pull and take it back to rebuilder and have them check it, as it is under warranty.

 

Thanks so far, 37Buick 66S!

[Drakeule]

Accelerator pump squirts beautifully. so what I have is an intermittent problem; I'll just have to wait until it misbehaves again.

 

If (probably when) it does,the first thing I'll do is peer into the throat and pull the accelerator rod again (switch off; I don't want singed eyebrows or worse!) and look for the streams of fuel. If none, I'll blow all out with compressed air and clean up with gumout, and blow it out again.

[Drakeule]

My son in law mentioned that ,very possibly, when my carb was glass beaded, some were left in the carb; causing the intermittent problem. Makes the best sense so far.

 

Any input on this ?

[jenz38]

Check also the Choke ,it opened correctly and not sucks to close position while accelerate?

Or an Air leak at Intake manifold to Head ,or at the Carb to Manifold Gasket ?.. seen often wrong gaskets there..

Check also your Wiper Hose  for Air leaks.

 

 good Luck, to find the Problem and keep us postin'

M2C

 

[jenz38]

When al it's ok...check our your idle mixture  is correct ?.. 

Screw for first start after Carb repuild should be 1,5 turns out.