Uh-oh...flooding

[TylerW]

Hey all:

My '71 has started suffering from a heat-soak flooding thing since the weather got warmer. The warmer it's been the worse it's gotten.

What happens is, if it sits and heat soaks an hour or so, it'll restart fine, but then loads up and tries to quit if i don't catch it and keep it running.

Today it had a really bad spell of it after I had been out doing video work in the 90 degree heat. It started quickly but then loaded up so bad it would not idle.

I let it quit and yanked the top off the air cleaner. The choke was wide open, but it had puked gas out of the center bowl vent and down onto the intake manifold.

I drove my truck on my errand and when I came back a couple hours later, the car spun a long time but started up and ran like usual.

I even caught this event on camera a month ago, before I got new exhaust on:
[ame="http://www.youtube.com/watch?v=pDfQWPDnFJo"]YouTube - ‪Chrysler starter workout‬‏[/ame]

Notes:

Hot starts are always quick, it doesn't normally spin for a long time before catching.

There's no other flooding symptoms. Runs good, idles good, even at 200 degrees.

There is the thick isolator under the carb. This is a Holley 2280 on a plain 318 and it's been upgraded from the quirky '71 style vapor system to the later type with 1 vent tank.

I forgot to re-install the rubber stopper that blocks the flow into the bowl vent to canister line..it's open all the time and there was some liquid gas in the line.

I am using the original non-vented gas cap and filler tube. I think Slantsixdan said that was a no-no with the 1-port tank..how come?

Does it sound like the vapor recovery system could be causing this?

Thanks!

 

[slantsixdan]

When the engine starts up just fine but then runs poorly, it suggests that the carb isn't boiling but the line between the fuel pump and the carb is getting hot. As soon as the engine starts running, that boiling-hot fuel is pumped into the carb and things get rough and choppy until cool fuel from the tank replaces the hot fuel. Work to reduce in-line heating of the fuel: slit a length of 3/8" fuel line hose lengthwise, push it over the pump-to-carb line, and secure it at bends and ends with hose clamps. Remove any metal clips holding this line to the engine.

Tell us more about the upgrade you did to the fuel tank venting system. What fuel tank did you use, and where did you run its vent? Does your 2280 have an external bowl vent (some do, some don't)? If so, where is it routed?

On your '71, the original fuel cap would be a pressure-vacuum vented item. If you are using a non-vented cap of some kind, that's wrong.

 

[TylerW]

Ok, here goes:

I removed all of the '71's original fuel system, all of it. It was rusted and totally unusable. I replaced it with the complete fuel system minus carb and fuel pump, from the '75 49-state 318 Duster I parted out.

That starts with the gas tank, which has one fuel line outlet and one vent port top center front. Also used the factory steel lines.

I installed the charcoal canister(3 port) in the factory location. Vent line from the tank is attached to the TANK port, Carb vent(it has one) is attached to the other large port which I think says CARB or BOWL, and the last, smaller line is attached to a ported vacuum source at the bottom front of the carb.

I am using the steel lines from pump to carb.

The carburetor is a 2280 with external bowl vent, as found on a 1984 Dodge D150.

The choke is electrically assisted, with a single-stage controller power by a tee from the alternator field.

I am using the factory '71 cap, my memory of that info wasn't correct obviously.

Those 2280s have a metal plate on the top of the airhorn, under which resides the accelerator pump linkage, power valve actuator and the bowl vent valve.

The bowl vent is supposed to have a rubber stopper that seals off the bowl vent at certain times, mine was missing. and I'm assuming I left it off when I overhauled the carb a couple years ago.

In fact I'm still trying to understand how this particular bowl vent functions, because from looking at my spare 2280, the bowl vent appears to be closed most of the time by a spring loaded arm.


I don't think it's starving when this episode occurs, at least it's not the main problem, because it's kicked gas out over the top of the carb at least twice.

The most strange part of it, is that until last night when I let it flood out and die, it's never spun more than three revolutions to start even after having heat soaked.

And, once it's running, it's a joy to drive. No stalling or flooding or anything.

I'm going to pull off the airhorn and see what I find this afternoon.

Thank you for the help.

 

[slantsixdan]

Sounds like a good, complete update of the fuel system. One thing to check carefully is whether the small diameter hose attached to the "PURGE" port on your charcoal can has any vacuum at curb (hot) idle. If it does, that'll explain the problem which you can remedy by installing a purge control valve (see here).

I am using the steel lines from pump to carb.

Insulate!

The bowl vent is supposed to have a rubber stopper that seals off the bowl vent at certain times, mine was missing. and I'm assuming I left it off when I overhauled the carb a couple years ago.

Fix that.

In fact I'm still trying to understand how this particular bowl vent functions, because from looking at my spare 2280, the bowl vent appears to be closed most of the time by a spring loaded arm.

This is the case with all makes and models of carb. The external bowl vent wants to be open only when the throttle is closed (curb idle), otherwise you'll get lousy gas mileage.

Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.

I don't think it's starving when this episode occurs

It's not. It's flooding.

Call up www.daytonaparts.com and see if they'll sell you a "DFV" (their improved inlet needle and seat design) for your 2280. Not sure if they make one to suit.

 

[TylerW]

Good deal.

I did some testing this afternoon. I went ahead and pulled off the airhorn of the carb. I found that the bowl vent valve was there, but installed the wrong direction, so I fixed that.

The floats were just barely a little high so I lowered them just a bit.Everything else inside looked fine.

I rechecked my lines at the canister just to be sure I had them connected correctly, and they are, but...I tried to blow back through the vent line to the tank, and couldn't. I removed the gas cap and tried again, and could not. Maybe that's normal, I'm not sure.

I let it run and warm up to temp, and a little over, with it in gear, then let it heat soak about 45 minutes with the gas cap OFF to take a tank pressurization issue out of the equation, and there was no hint of fuel out of the carb and it started and ran fine.

I did notice that the carb is pretty HOT after it heat soaks, even with the thick spacer under it.

Returning to the tank venting....the other day I had the fuel sender out to see why it wasn't working, and when I put it back in, fuel started siphoning out of the output all by itself as I tightened the lock ring down.

I got out from under and loosened the cap and got a whooosh. This is probably nothing..I would think if the tank was actually sealed tight the engine would quit due to not being able to pull gas up.

The car is still cooling down so I'll give it an hour and see if I get anything. If not then I'll drive it around in the heat of the day and test it that way.

I'll insulate those lines. Speaking of that issue, between my brother and I, we have 3 running Mopar V8s currently and all of them react differently to the hot weather starting.

Mine you know about. My brother's '83 D150 w/ tired 318 and BBD spins and spins before it catches when hot. His '73 Dart Sport w/ 440 and a Holley 4bbl starts and stalls at least twice on heat soaked starts. It doesn't flood, it just starves until it gets gas back in the carb.

 

[slantsixdan]

See here for a description of how the pressure-vacuum fuel cap is supposed to work.

Inability to blow freely to the tank thru the vent line is normal.

 

[TylerW]

Well I've had another project going so the Plymouth got pushed aside temporarily, but now I'm back to it.

By chance I've discovered what the problem is. I had the car loaded up to go to the car show Saturday morning. Started it up, runs for 5 seconds then begins to sputter and lope. Pop the hood and sure enough there's gas dripping...again.

I got the hammer and tapped the side of the carb by the fuel inlet and everything straightens up. I didn't drive the car, all I needed was to have gas going everywhere on a hot engine.

So obviously what's happening is the needle valve or the float itself is hanging open when the carb starts cooling back down and contracting.

My brother had a Holley 2245 that did this as well because of the float pin binding, so I'm going to look at all of this very carefully.

 

[TylerW]

And now the moment dozens of FABO members have been waiting for...the cause and solution:

When I de-topped the carb again and looked closely at the floats, it was apparent that the driver-side pontoon was against the rear wall of the carb when the fuel level was low.

The reason was that someone had bent the float "arms" to adjust them instead of bending the tab that rides against the inlet needle.

Once the floats were straight and the level adjusted properly everything seems back to normal.

These carbs have the nitrophyl floats btw.

 

[65Val]

Tyler...thats good troubleshooting right there. Someone will have (or has) exactly your problem and will benefit from your expertise!

That deserves an "atta-boy"!!