[RH68]

I’m having problems getting my engine started after it has been running. If started from cold it fires right up. However, once warm it wants to flood when I try to start it. It is a 400 with an edelbrock performer carb. I made a few changes recently that I thought may have caused this such as replacing the fuel pump and replacing the spark plugs with AC Delco R43S plugs.

Here is what I have done so far to troubleshoot:
-measured fuel pressure from the new pump. It is 6psi.
-took the carb apart, cleaned the needles and seats, and checked the float heights.
-re-gapped the spark plugs from .035 to .042.

I didn’t use to have this problem before this year. My technique to start the car when warm is to either just turn the key or pump the pedal twice then start.

When I try to start it it attempts to fire but then dies and then floods. I often end up having to start it by holding the pedal to the floor and cranking for a while.

What else can I try?

Thanks!

[PontiacJim1959]

Here is what I would try.

First, get a new needle & seat assembly. It has been my experience that there are different styles of needle & seat combo's and some work better than others due in part to the shape of the end on the needle and how it seals int the seat. Some do not seat well enough to hold off the pressure from the fuel pump.

When you shut the engine down, there is still pressure/gas in the fuel line. A needle & seat that does not seal well, can allow the pressure still in the line to push the gas past the needle/seat and actually flood the carb. Heat from the engine can contribute to this problem as the gas may want to boil/expand further and contribute to overpowering the needle/seat and flood the carb.

Next thing would be a fuel pressure regulator. 6 PSI may actually be too much even though the instructions say it can be 6 PSI. 5/4 PSI may make a difference and allow the needle/seat to hold off the gasoline pressure when you shut the engine down.

I have also had times when I had to drop the float level more than the required measurement This will shut the needle/seat just a little earlier when the bowl is filled and give a little extra room for fuel expansion or for some to leak in past the needle/seat. Not really an issue when running as the gas will continue to flow as it normally would when the float drops.

Check to make sure the float is good. Not knowing if you have brass or the foam style, the brass float can have a pin hole and allow gas to get inside and get "heavy" so it does not work as it should. The foam type can get saturated and become "heavy" as well. This was at least the case on the original Q-jets.

Do you have a 1/4" fuel return line going back to the tank? This can be a help in reducing line pressure.

Just a few things I might check because your description at this time sounds like a flooding issue.

[Navy Horn 16]

If it's flooding, stop pumping the carb (sending multiple pump shots into the intake) before you try to start it.

[Sirrotica]

It could also be vapor lock, aggravated by gasoline that boils at a lower temperature due to ethanol being added to it. When gasoline boils in the lines it turns to a vapor which cannot be controlled by any needle and seat, and the floats cease to work as they cannot float in a vapor.

If standard non ethanol fuel is available in your area, you might try filling the tank with standard gasoline, and see if by raising the boiling level over the ethanol blended fuel it affects the hot start problem. If it does you might try insulating the fuel system from heat.

My father had a motorhome that suffered from this affliction, and we had to remove heat from the fuel system to make it drivable in hot weather. It would run and start in cool weather, but as the ambient temperature rose problems increased as far as running and restarting hot.

Just a suggestion, you know all the symptoms of the problems with hot start, and my thoughts could be just a shot in the dark, not knowing all the symptoms and unable to ask direct questions, it's just basically a guess based on previous experiences.

[Jerry H.]

^^^^
Today's crappy gas causes more problems than you think.

[Schurkey]

Originally Posted by Navy Horn 16

If it's flooding, stop pumping the carb (sending multiple pump shots into the intake) before you try to start it.

Pump the thing about 1/8--1/4 of a full pump. Just enough to set the choke if the choke is cool enough to move; and to blow a hint of fuel into the manifold via the accelerator pump.

[kyle_blake]

I use to tap the top of carb with rubber mallet to release the stuck float but never owned one.

[389]

Pull all the plugs and dry everything off.. Crank the motor without the plugs in it a little.. Make sure the plugs are gapped .030 and are dry and put them back in.. All widening the gap does is invite spark leakage at weak places in the wires..