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Stalling on downgrade stops...common?

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Jim Lee

Jedi Trainee
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Hi all,

It has been a while but finally got my TR3a back on the road where it should be. It is running like a top but the one question I have for you all is if you ever have a problem when you come to a stop on a downgrade and you stall out before you can get your foot from the brake to the gas to keep the revs up a little. My sequence of events is:

On slight downgrade, put car into neutral put on brake. While I am coming to a stop, and before I can safely take my foot off the brake I can here the engine get lower and lower until it just cuts off as I sit there at the stop sign or light. It starts right with no problem and will idle as well as it normally does for the rest of my stop.

If I am really quick I can sometimes save it at the last second but usually I am a moment too late. This is fully warmed up.

Thanks very much and happy anglophilic motoring.
Jim Lee
1959 tr3a
 
When it re-starts, any black out the tailpipe?

I would think float level issues, flooding over on a down angle.

You aren't alone.....see how many cars stall at the bottom of a freeway offramp.
 
Double-check float height and mixture adjustment. Because of the way the float bowls are mounted in front of the jets, the TR3 carbs go slightly lean under those conditions; but it shouldn't be lean enough to stall. Also try lifting the carb pistons to the top, and check that they fall smoothly and land with a distinct click. Any binding whatsoever can cause extra-lean mixture on deceleration.

Bumping up the idle rpm a bit might help too. It's not unusual for the tach to read high at idle.
 
I've never known why, but my TR4A always does that, too, but maybe to a lesser extent. While going downhill to a stop, I throw it in neutral and keep one foot on the brake and the other on the accelerator.
 
I suppose that I would try adjusting the float height both ways. It could be leaning out or flooding though I would think it would be more probable that it is leaning out since I can restart it so easily. If it was flooding I would think it would take longer to restart. I am usually able to just push the button and it picks right up. If it is not getting enough gas, leaning out, I should lower the float right?

Thanks very much,
Jim Lee
 
Heel-and-toe.
 
Reason I asked about black smoke on restart.
Momentary richness will give you a puff of black on restart, enough to identify, usually.
If no black, it's lean.
To richen if lan due to low fuel, you want the fuel level higher in the float bowl, and not a handful, just a smidgen.

My thoughts on lean-out, downgrade, or long, hard stop, always was the float bowls in front of the carb body.
The main venturi has to provide a suction point for the fuel (main jet), but look how far away the bowl and float valve is from that point.

Cut out a picture of your carbs, side view, hold it at an angle, look at where the fuel level is in the main body, now add in the deceleration force of a hard stop on said downgrade, and the throwing of the fuel forward.

I've seen both (except it was a 4 that was rich), where the float level was high, but not astoundingly so, and the float arms were sluggish, best way to describe it.
Coming down off a grade, decelerating, seemed to fill the bowls quite a bit, to the point of spillover, get stopped, it all washed back to the mains, and the car quit.
Restarted immediately.......finally got the puff of black, knew where we were heading.

No rich, then, look at you picture and see.
If they put the float bowls in the back, it would be different symptom.

You want an odd one to figure out......a GM 2-jet (2bbl) mounted backwards on a 49-51 Merc intake, to keep the throttle on the correct side, and the sudden lean drop on hard acceleration, as all the fuel piles up against the now back wall of the float bowl......
 
Per usual you all were spot on. I raised the float level some (very unscientifically I might add) and all has been well since.

I love driving this around. I am going to post another question about a notchy steering box. It is fine on the road but not much fun in parking lots...which I do my best to avoid. I have done some work on the box in the past and am not sure if I helped it or hurt it. It has always leaked albeit slowly.

Thanks very much,
Jim Lee
 
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