Packard Forum Index » Post-War (1946-54)

Hi, all. I am a relative newcomer, having bought my 23rd Series Super Eight in February, and only recently starting to enjoy it on the road up here in Michigan. I've had a couple of minor questions that this forum has helped on.

Here's a new one. I've never had trouble starting the engine until this past weekend (twice)...and it was under identical circumstances. I guess I would call it a "hot restart" situation. I drove the vehicle for 20 min, parked and shut the engine off for 20 min. Then, when I went to start it again, had significant difficulty getting the engine going. Again, this happened twice. I should make mention that the vehicle is fitted with an electric fuel pump. I'm not clear on whether my difficulty is due to a flooded engine, or a situation involving vapor lock. Both times, after much effort and pausing to rest, I managed to get the engine started again. This does not happen when I restart the engine after just a few minutes of having been shut off...only when it has been around 20 min or so...so I know it must have something to do with the fact that the engine is hot.

It would be good to know what I should do when I encounter the next situation such as this...if nothing else than to avoid embarassment! Is it a technique that I'm missing? Remember, I'm new to the world of carburated engines. Should I (1) jog the fuel pump and pump the accelerator first to ensure the carburator is full assuming that due to the hot conditions the fuel has vaporized or (2) do I actually have a engine that has flooded somehow due to the thermodynamic conditions and perhaps I need to floor the pedal first to open the choke?

Other than this experience, the vehicle seems to operate flawlessly.

Comments/suggestions??

Can I assume the electric pump is mounted in the rear near the tank? If so vapor lock is probably not the problem. Have you checked the line for pressure? Leaking needle and seat and/or too high a pressure could be the problem (leading to flooding), or perhaps a balky automatic choke. If holding the gas pedal all way to the floor (beyond what triggers the starter motor) help it get started, then clearly flooding is the issue.

The electric fuel pump is mounted in the rear near the gas tank. I didn't try flooring the pedal until way into the agony of starting the motor...and while I don't recall that necessarily having an immediate effect, it may in fact have been what was necessary to get us on our way.

What I'm trying to understand is why this is only happening under these conditions (restart 20 min after sitting hot). Maybe next time I should go ahead and floor it immediately to open the choke while cranking.

In addition to vapor lock, heat can cause fuel percolation in the carburetor. This really nothing new (just forgotten knowledge) as I've seen references to the issue in shop manuals printed some 60 years ago, but fuel blends of more recent years may be more prone to this phenomenon.

Also known as a hot soak or fuel foaming, the condition occurs when fuel in the carburetor bowl gets hot emough to literally boil and turn into a foam, which spills out the bowl vents and down the throat of the intake manifold - resulting in a flooded condition.

In addition to the Reid Vapor Pressure (RVP) rating of the fuel (which is more of a problem with winter blends in recent decades), engine temperature actually rises for a period after shutdown. First and foremost, make sure your engine cooling system is in good working order - so that your engine isn't running too hot.

About 30-40 years ago, automakers further attempted to address the problem by using an insulator rather than just a gasket for the base of the carburetor. In another forum some years ago, I suggested that a V8 owner lay hands on a piece of phenolic board (such as what is used for printed circuit board), trim it to the shape of the gasket and sandwich that between two new carb base gaskets. It solved his problem. If phenolic board had not been available to him, I would have suggested a thin piece of maple wood.

Ultimately, high-pressure fuel pumps used with modern EFI systems rendered all of this moot.

You should check the fuel pump pressure. A simple vacuum gauge/fuel pressure gauge available at almost any auto store will have one. The pressure should be about 4-5 p.s.i. but not more than 6 if I recall correctly. If the fuel pump does not have a pressure regulator then perhaps it is pushing fuel at too high a pressure and as already mentioned it is getting past a faulty needle and seat.

Also didnt some of the 23rd series cars have a Carburetor Heat Shield? If your car was supposed to have one, perhaps it could it be missing?

If the shield was required and is missing it could also lead to the condition that Brian (BH) described. I belive the shield was only used with certain Carburetors.

I believe the heat shields were included on all of the Customs (356). I'm not sure about the Supers or Eights. I have seen those both ways. Even if they were not original, they seem to help with the hot start problem with the newer formulated fuel. My 49 super (327) has one as does my '47 custom (356).
I don't use an electric pump on my '49. But my '47 has one that I have disconnected. I left it so I could reconnect it if I need it. So far, I haven't reconnected it.

If there is a strong gas smell or gas oozing from the carb then the carb bowl vent is probably plugged up with mud dobber nests or something.

G'day all, I would suggest that one of the reasons Packard fitted the vacuum start switches to the Carter carburettors on the early 50's, 6V cars, so that you had to floor the throttle to activate the starter, was to clear the engine of excess fuel. I also use this technique on my 35 and 38 Supers to restart them after a long run on a very hot day. Particularly if theh have sat for around 15-20 minutes. It works for me anyway. Best regards Peter Toet

You could put a switch on the fuel pump and shut it off a few minutes before you stop the car.