Fuming over my carb, help!

[Normspeed]

OK, you are likely sick of hearing me whine about the raw fuel smell in my car. In another thread I recently went through the entire fuel system, made some mods and improvements, and yet yesterday I parked it hot, did not take the time to turn off the electric pump and let the carbs run dry. Came out an hour later and I could smell my car from 20 feet downwind. Popped the hood, the fuel pressure was holding residual 1 psi. Gas seeping out of the front carb and down the top of the intake manifold. Engine flooded.

You carb gurus out there, please tell me what I'm missing. I've been through my carbs carefully, the floats are set lower than spec. No chokes. They run great, but something in that front carb ain't right! I'm sure the problem must be in the middle section (fuel bowl section). What could be wrong that would allow the carb to seep gas down into the carb throat? Maybe the ball check valve under the brass pipe plug? Help guys, these fumes are killing me! If I can't fix this, I'm gonna buy an old Ford with those nice Strombergs:rolleyes:

[Young Ed]

Bad needle and seat perhaps allowing the fuel pressure from the system to enter that front carb?

[GeorgeLeonard]

Maybe Im not understanding something here. How does leaving the electric fuel pump on while parked, cause the carbs to run dry?

[Normspeed]

Ed, I swapped in a new needle and seat a week ago. Didn't help.

I'm thinking, I have three center carb bodies. One on that carb, one with stripped inlet threads, and one that just never ran quite right. Maybe I can do a test, fill all three float bowls with gas, and see where the heck mine is seeping from.

[Norm's Coupe]

Are you sure the electric fuel pump is working right? Your problem sounds like what happened to me when my bellows electric pump went bad. The carb would overflow and flood the engine out. Got to the point that you could not even start the car and keep it running. Went back to the mechanical pump and no more problems.

I know you are not using the Bellows type pump, but it still could be a bad pump.

[Norm's Coupe]

Shel,

When I had the electric pump I would also turn it off when I shut the car down. However, as soon as I turned it back on to start the car the pump would fill the carb and overflow it within seconds, after it went bad. I would check the pump if I didn't have the problem using it before. It could have went south on him.

[Fireball]

My bet is that when parked hot the heat boils the fuel in your carb Norm. Makes it expand and seek it's way out...

[Mark Haymond]

When you swapped in a new needle and seat a week ago, did you recheck the float level in that carb? Even tightening or loosening the fuel inlet seat in the carb body will change the float level.

[greg g]

do your carbs have the little clip that hold s the float hing pin down in the slot?

[55 Fargo]

Bad needle and seat perhaps allowing the fuel pressure from the system to enter that front carb?

Ed, I would concur, bad seal at needle and seat, and/or float that has a very slight leak.

Lets look at this from a plumbing perspective, the gas comes from the tank thorugh fuel pumps, through pressure gauge, splitters etc. Then enters carb, where the needle and seat are the on/off shut off valve, (the tap), the seat and/or needle leakes, gas fills bowl to top, the float has risen to the top.

The needle is pushed into the seat, but cannot shut off the supply of pressurized gas, heat exacerbates the situation allowing the fuel to expand, resulting in flooding, and/or leakage at carb body.

Normspeed how does that theory sound...............Fred

[claybill]

NORM BABY...RELAX,!!!!! buy another carb on ebay for 25 bucks...install it..use parts from your carb and you are OK..

BILL

[Normspeed]

I appreciate the suggestions from all. The problem only happens with the motor off, warm. If I switch off the pump and run the motor til the carbs go dry the problem doesn't happen.

When I run the fuel pump I get a solid 3 psi at the fuel block. That's with the Holley pressure regulator set at 3 psi. I replaced the needle and seat and rechecked the float level.

Today I did the comparison test with three center sections, filled all fuel bowls and none of them showed any unusual seepage. Tested three floats for leaks, all checked out good. I put the best looking one back in and set the float level on that one. It's all back together and running fine so time will tell...

Greg, yes it does have that little horseshoe clip in place.

If I buy another carb I might take the plunge and shop around for a really good older rebuild or a NOS. There's a decent older rebuild on the bay for $200 right now. Either that, or if I can't get it right, I may need to go with the setup that Blueskies has. Just tired of smelling raw gas is all.

At 5pm today I'm meeting up with a guy who says he has a 55 Pontiac 4 door, needs a lot of work, no seats or motor but has a title. Says he will take $200-300 for it. I figure it's worth a look, ya never know. And if it were a 4 door hardtop, might be worth adding to the project pile. I'll bring my camera:D

Thanks again for the troubleshooting help.

[Young Ed]

Did they have 4dr hardtops in 55? Lots of them didn't come out until 56

[Normspeed]

I'm not sure. I think you're right Ed.

[Norm's Coupe]

Did they have 4dr hardtops in 55? Lots of them didn't come out until 56

Not sure about the Pontiac without looking in my book, but I know the 55 Old's had a 4 door hardtop. Since they are both GM, my guess is there is a Pontiac 4 door hardtop too.

[Young Ed]

OK you guys got me curious so I looked it up in my book cars of the fabulous 50s. Norm is right Olds had a 4dr hardtop in 55 along with Buick. The rest of GM however waited until 56. Ford and Mercury started in 56 along with the DPCD lineup.

[claybill]

norm.....i have bought 6 carbs on ebay over the years all under 40 bucks and they work fine......with a little cleaning. save your money. pass on the pontiac..lots of work lots, drive your ply!!!

did you ever try to ELIMINATE the elec fuel pump? to test?.......i dont have one and it runs ok..

bill

[Don Coatney]

Normspeed;

Guess I must ask why you are using an electric fuel pump. I have the same basic setup as you have (with the exception of an electric fuel pump) and my B&B's do somewhat leak. But with my stock fuel pump I do not have the same problem. My engine has never failed to start and I do not have any raw gas smell except a slight wiff on initial startup after not starting my car for a couple of weeks. Have you tried noseplugs????????

[Normspeed]

Well Don, I've had my share of failed mechanical pumps on flathead sixes. One bad diaphragm resulting in a crankcase full of gasoline, two that leaked oil, one replacement Airtex that had a bad knock. I like the instant starting no matter how long the car has been stored. Plus they are easier to replace on the roadside, you can carry a spare easily because they are smaller than a mechanical pump, and there are ways to wire them that might frustrate or slow down a dirtbag car thief, especially if it quits on them in traffic.

Here are some Pontiac photos. Rust free car except for two small holes in the front floorboards. No motor or trans. Needs windshield and some side glass. Has every piece of trim, interior and exterior, except taillight lenses and hood ornament. Only dent is where some clod jumped on the hood ornament, broke it and dented that part of the hood. A good deal for $300, and he has the title as well. Looks like Riviera or Wildcat rims (4). If this were a 2 door I would buy it in a heartbeat.

[p10plymouth]

I appreciate the suggestions from all. The problem only happens with the motor off, warm. If I switch off the pump and run the motor til the carbs go dry the problem doesn't happen.

Is it safe to say the car runs fine other than the start problem? If so .

I am a firm believer in a 4 gas analyzer test , just to see how its burning while its running.. If OK.. I would take the gas cap off to see if you have a vent problem . (or check the vent) IF all checks good I would consider putting a T from the carb back to the tank and make a gas return so any fuel can be returned back to the tank.. and hopefully eliminate your problem...

[moparalltheway]

Mine does this only if I let the tank run dry. After I refill and start the carb spills gas. I pull the needle and clean it and all is fine after that. Either the float is sticking on bottom or trash.

[tinlizzy]

Nice Pontiac, go for it. There is a 55 I think Buick or Olds near my home sitting in back of a fence, been there a long time. Be a good project for someone if they had the fianances.

Lee

[radioguy7]

OK, you are likely sick of hearing me whine about the raw fuel smell in my car. In another thread I recently went through the entire fuel system, made some mods and improvements, and yet yesterday I parked it hot, did not take the time to turn off the electric pump and let the carbs run dry. Came out an hour later and I could smell my car from 20 feet downwind. Popped the hood, the fuel pressure was holding residual 1 psi. Gas seeping out of the front carb and down the top of the intake manifold. Engine flooded.

You carb gurus out there, please tell me what I'm missing. I've been through my carbs carefully, the floats are set lower than spec. No chokes. They run great, but something in that front carb ain't right! I'm sure the problem must be in the middle section (fuel bowl section). What could be wrong that would allow the carb to seep gas down into the carb throat? Maybe the ball check valve under the brass pipe plug? Help guys, these fumes are killing me! If I can't fix this, I'm gonna buy an old Ford with those nice Strombergs:rolleyes:

Ok, forgive me if I sound simple minded with my suggestion, but why not just install an inline fuel shut off for the time being until you can figure this out?? It will help answer some questions too, if you are still seeing fuel leaking out of your front carb then you know it's not coming from your tank and is most likely expanding and leaking out. To me its an obvious temporary fix to your problem and might help you find the answer. Just a new guy here but not a newbie to skinned knuckles

[Dennis Hemingway]

If you buy that Pontiac you will have to buy the Power Wagon to tow it around.

Dennis:cool:

[Norm's Coupe]

Normspeed,

I had an Airtex pump that knocked like crazy too. Sounded like a valve knocking. Replaced it last fall with a new A/C mechanical pump and it's nice and quiet. When looking at the two together, you can't tell the difference. Both have the glass bowl. The A/C pump uses the same number as the Airtex does, #588.