Any carburetor gurus left out there?

[CigarStone]

I have a 79 F-150 with a 351 modified which has a 600 CFM Edelbrock 4BBL and high rise intake manifold.

The motor is a new green motor which is broken in and working fine but I do not know enough about carburetors to know how to address this issue.

The truck sits for months at a time and is often difficult to start because (I assume) that the gas has evaporated from the float bowls and even though I have two batteries, hooked in parallel, when the weather is extreme I can get close to running them down until I get it started.

Here is what I am doing, what is happening, and what I need to know.

I have bypassed the mechanical fuel pump and installed an electric one and I have installed an electric choke. These work fine except when the truck has sat for a while.

My first step is to turn on the ignition (to accessory) and let the fuel pump come up to pressure. Then I set the choke by pushing the accelerator to the floor and hold it a few seconds to let fuel get into the float bowls. I will most often (depending on how long it has sat and how cold it is) have to push the accelerator to the floor a couple more times before it starts and then the choke doesn't work properly and I have to play with it to keep it running until the engine warms up and will idle on it's own.

Question #1 Am I correct in assuming the fuel is evaporating?

Question #2 Should I hold the accelerator down longer to allow it to pump more fuel into the bowls?

Question #3 Should I push the accelerator to the floor multiple times?

Question #4 Why, even though it's cold out, won't the choke work if I touch the accelerator more than once?

Thanks

 

[AVB]

Not a guru by any stretch but I built a 351 Windsor for my Uncles tow vehicle with an Edlebrock 600 and an electric fuel pump too. Mine was a vacuum secondaries model and was attached to a dual plane manifold since I was looking for torque.

Your starting procedure is pretty close to what I remember, gas to floor for a count of three and then fire it up. It almost sounds like your choke is binding due to not enough clearance when cold OR the choke itself isn't adjusted properly. The electric chokes on the Edlebrocks are damn near bullet proof so I'd first check for binding and then read up on adjustment.

 

[npedersen]

Question #1: Fuel does not evaporate like people think. The combustible does how ever and the fuel turns to varnish. Fuel loses it's volitity in as little as a few weeks. If you know you are going to let it sit for a while you should put a product such as Sta-bil in it.

The jets in the carb are most likely covered in varnish and the fuel is not atomizing correctly. That is the mixture rate of the fuel when it is sprayed into the air stream.

It is possible that the accelerator pump in the carb is not creating sufficient "suction" and not drawing the fuel correctly. The choke should be electric on the carb, check the connections a check the voltage both hot and cold, there should be a variation. When the temp is cold the resistance in the switch is differant than that when it is hot. If it is vacuum operated, check the vacuum line going to the choke.

The other possibilty is in the ignition, it may not be properly advancing or retarding when it is cold, check the vacuum advance lines for cracks.

Hope this helps.

Nick

Oh yeah, I find while diagnosing a problem the correct cigar is absolutely neccessary, otherwise proper thinking can not occur!

 

[Devil Doc]

Boy its been awhile. Pump the piss out of it and keep crankin'.

Doc.

 

[CoventryCat86]

Boy its been awhile. Pump the piss out of it and keep crankin'.

Doc.

:laugh: :laugh:

LMAO! That's exactly how I start my '78 Chevy K-20 with a 350 and an after market Edelbrock 4bbl. The truck is lucky if it gets run once a month.

 

[grateful1]

Boy its been awhile. Pump the piss out of it and keep crankin'.

Doc.

:laugh: :laugh:

LMAO! That's exactly how I start my '78 Chevy K-20 with a 350 and an after market Edelbrock 4bbl. The truck is lucky if it gets run once a month.

...and my '71 Dodge B-200 Van(gone now)...just go at it and away we went.

Oh, yea these are NOT Fords! :sign:

---------------------------

Ok - the above suggestions are excellent. NP's pointing in the right places! :thumbs:

 

[DanTheMan]

Ehhhh- we're not talkin' rocket science here boys-

Remember that a carburetor is nothing more than a toilet flushing fuel down the intake with a couple enhancements. When the engine is cold and on initial start-up, the only fuel that gets into the engine is when you- 1) pump the accellerator pedal and the accellerator pump squirts a good dose of fuel into the intake, and 2) when you close the choke plate over the top of the carb and in essence put your hand over the top of the carb, fuel gets pulled past every available orifice until the choke pull off pulls the choke back against the predetermined measurement of the choke plate of usually about 3/16"-1/4", once the engine fires up. Carburetors were highly inefficient and hence why they have been replaced with sequential injectors that double squirt on cranking cold right ahead of the intake valves to fire the engines up after a couple revolutions or else we go into the dealer complaining of an extended crank cold.... haaaa
But as for your condition- with the two scenarios above mentioned- it sounds like when you turn on the key and fire up the fuel pump to fill the bowl etc. that's all well and good, but remember that when the key is on, the choke is heating up, and your cutting off the amount of time the choke set may completely close off the air on top of the carb and not allow it to suck major fuel thru the main jets when needed. Most chokes have an adjustment to allow you to increase or decrease choke pull to keep the plate closed longer or shorter. (sometimes marked lean rich on the choke housings). So you may need to adjust the choke because of the heating element kicking your choke back while your filling the bowl up to the point the fuel pump kicks off. The other kicker is that when you've ran the key and warmed up the choke somewhat, the action of kicking the throttle actually unloads the choke to kick off the fast idle cam etc. (Like when you rev the engine up to kick the choke off).
Like I mentioned the carb being its inefficient self, when you step on the accellerator pedal two or three times you're squirting fuel into the area under the carb, and as the engine is cold, the cold metal grabs all the fuel it can. So until the fuel dissipates and gets into the cylinders on first crank, the cylinders won't fire.
So to help your condition, 1) be sure your choke is set up tight enough to still be closed until the engine runs. and 2) as mentioned by some of the other botl's- pump the gas pedal several times after your pump shuts off to get the fuel into the cylinders.
Piece of cake huh? Join us next time when we talk about speed density fuel systems with maf/map sensors and the like... naaaaaaaa- let's smoke a cigar instead...

D

 

[anvil]

Boy its been awhile. Pump the piss out of it and keep crankin'.

Doc.

Goddammit Doc, you made me choke on my beer reading that :laugh: :laugh: :laugh:

 

[LedMizer]

The truck sits for months at a time and is often difficult to start

I have the exact set-up in a '78 F100 Custom. It's mostly my weekend ride for hunting, fishing and trips to Home Depot.

Can't add anything to the comments above other than to say mine behaves much better if I make certain not to let it sit too long. In fact, I drove it to work two times last week (~250 miles) and found my oil pressure up from the usual measley 15 to the mid-20's. Go figure.

I will also assume you've ruled out any issues with the spark and you feel confident its a fuel problem.

I think you will have trouble starting anything that sits "for months at a time," especially with todays gasoline formulations. I know its raising hell with outboard motors in my area.

 

[CigarStone]

Thanks guys!

I am going to go on the assumption that my fuel is breaking down and not evaporating :thumbs:

I am also going to go with the idea that running my fuel pump for 7-8 seconds is heating up the choke :thumbs:

Most of all, I am going to pump the piss out of it and go :thumbs:

Is it possible that, based on the good input here, I am dumping the varnish into the cylinders and until I dump a bunch of new gas on it, it won't fire.......but I have now loaded it up so bad that maybe the choke is still working but it won't fast idle due to the massive amount of fuel I dumped in?

 

[BlindedByScience]

Oh yeah, I find while diagnosing a problem the correct cigar is absolutely neccessary, otherwise proper thinking can not occur!

I'm an electrical engineer, not a mechanical or chemical engineer, but for some reason smoking a cigar while fiddling with pumps that squirt gasoline and vaporize it just doesn't sound like a great idea.

Just a thought...... :laugh:

Good luck with the Edelbrock - B.B.S.

 

[grateful1]

Oh yeah, I find while diagnosing a problem the correct cigar is absolutely neccessary, otherwise proper thinking can not occur!

I'm an electrical engineer, not a mechanical or chemical engineer, but for some reason smoking a cigar while fiddling with pumps that squirt gasoline and vaporize it just doesn't sound like a great idea.

Just a thought...... :laugh:

Good luck with the Edelbrock - B.B.S.

Where's Wilkey when you need a good editorial!

:laugh: :laugh: :laugh:

 

[CigarStone]

Oh yeah, I find while diagnosing a problem the correct cigar is absolutely neccessary, otherwise proper thinking can not occur!

I'm an electrical engineer, not a mechanical or chemical engineer, but for some reason smoking a cigar while fiddling with pumps that squirt gasoline and vaporize it just doesn't sound like a great idea.

Just a thought...... :laugh:

Good luck with the Edelbrock - B.B.S.

I am also an electrical engineer and while it has been suggested many times that the ember from a cigarette or cigar will not light gasoline, I am with you and will put the cigar down before.....as Doc says.... pumping the piss out of it!

 

[jfields]

Jeff,
Let's take a look at it tommorow, or Friday. Could be anything from incorrect spring tension on the choke heater, to the choke pull off not working properly.

 

[CigarStone]

Jeff,
Let's take a look at it tommorow, or Friday. Could be anything from incorrect spring tension on the choke heater, to the choke pull off not working properly.

This should be good! My hillbilly neighbor at the cabin is a mechanic, Paul used to be, and once Bob enters the conversation we will have this baby popping wheelies and pulling 10 second quarter mile runs!

 

[roscoe]

I built a 66 Shelby Cobra replica about 8 years ago. It has a 351W, Aeromotive electric fuel pump and a 650 Barry Grant Speed Demon carb. During the winter months the car just sits in the garage.

We had a warm day on Monday and I rolled her out for a short drive. I think the last time I had her out was Christmas. Once the fuel came up to pressure I hit the starter and pumped the gas. I have no choke on the carb by the way. After a few sputters she lit right up. Never had a problem with starting. I also never used that gas stabilizer additive.

My first response to you would be to junk that Edelbrock carb and get either a Holley double pumper or Demon.

Roscoe

 

[mmburtch]

Oh yeah, I find while diagnosing a problem the correct cigar is absolutely neccessary, otherwise proper thinking can not occur!

I'm an electrical engineer, not a mechanical or chemical engineer, but for some reason smoking a cigar while fiddling with pumps that squirt gasoline and vaporize it just doesn't sound like a great idea.

Just a thought...... :laugh:

Good luck with the Edelbrock - B.B.S.

I am also an electrical engineer and while it has been suggested many times that the ember from a cigarette or cigar will not light gasoline, I am with you and will put the cigar down before.....as Doc says.... pumping the piss out of it!

Its true it won't ignite the gasoline. The fumes, now that's a different story.

 

[LedMizer]

I should have posted this before. The link will take you to a site caled ProjectBronco. This is a great source for the 79-79 Ford Truck and Bronco fan. Lots of good information, parts suppliers, etc. Worth a look for this and future questions.

http://www.projectbronco.com/

 

[npedersen]

Oh yeah, I find while diagnosing a problem the correct cigar is absolutely neccessary, otherwise proper thinking can not occur!

I'm an electrical engineer, not a mechanical or chemical engineer, but for some reason smoking a cigar while fiddling with pumps that squirt gasoline and vaporize it just doesn't sound like a great idea.

Just a thought...... :laugh:

Good luck with the Edelbrock - B.B.S.

I am also an electrical engineer and while it has been suggested many times that the ember from a cigarette or cigar will not light gasoline, I am with you and will put the cigar down before.....as Doc says.... pumping the piss out of it!

Its true it won't ignite the gasoline. The fumes, now that's a different story.

Sorry, I forgeot to that a disclaimer/warning note with this is required this day and age to prevent people from using common sense and to avoid a law suit :sign:

WARNING: Do not use open flame or smoke around gasoline fumes at any time. If you were to get that close your cigar would be ruined and the wife would say "you dumb a$$" while sitting by your bed side picking out a new face. :laugh:

 

[DanTheMan]

hmmmmmm- ok a quick off the cuff question- to anyone that's worked on cars, particularly with carbs....

You crank the car over and at first you're scared by the loud "bang", then the bottom drops out of your stomach when you see the residual flames flickering out of the top of the carb... 1st instinct???

a nursery rhyme comes to mind- " he huffed and he puffed and he blew the...." flames out???

It's amazing how much air you can deliver when the adrenaline kicks in....