How to Start a Carburated Motor in Any Situation

[KMD88 2]

This is embarrassing, but I have to put my pride aside for this one.

I've had my 69 Mach 1 since March. I love it, and I've been very lucky with the condition it was in when I purchased.

I was considering going EFI to make life easier, but the mechanic I work with was pretty against it; citing nothing but problems with each conversion he worked on previously. I have a 351 Windsor, and besides an engine swap, he told me to stay carburated for the time being. In addition, the mechanic said the carburated looks to be timed/calibrated properly.

I'm fine with this, except I just can't seem to dial in exactly what the car needs to start sometimes.

Here's what I've deciphered:

• When I haven't driven the car for two days or more, two full, slow pumps on the gas will do it.
• When I drive the car around, leave it for 5 minutes, then start her back up, I just put my foot 3/4 of the way down on the gas and turn the key. Starts right away.
• But after driving, then leaving her for an hour or two and coming back, it's sometimes a crap shoot. I've flooded the motor a couple times trying to figure it out.

So all this is to say, is there a rule of thumb or a method to really know what the engine needs? I'm getting my car back from the mechanic this week, and I don't want to be the newbie that can't start his own car right away.

I've searched online for help, but there's very little about starting carburators online. Or maybe I'm not using the right search terms.

Either way, would appreciate your advice. Again, embarrassed to ask, but you have to start somewhere.

Thank you.

 

 

[RogerC 136]

Is the choke set and working properly? I had a 79 with an earlier 302 in it. A couple of quick pumps of the gas pedal, hit the starter and it would fire right up every time.

[Brian Conway 264]

Some info would be good ?  Motor/carb ?   OE or after market ?  Brian

[KMD88 2]

23 minutes ago, Brian Conway said:

Some info would be good ?  Motor/carb ?   OE or after market ?  Brian

351 Windsor, Carb is a 600 CFM Classic Holley Carburetor

[KMD88 2]

44 minutes ago, RogerC said:

Is the choke set and working properly? I had a 79 with an earlier 302 in it. A couple of quick pumps of the gas pedal, hit the starter and it would fire right up every time.

Hi Roger. Choke is set and works fine. So no matter when you were starting the motor (cold or otherwise) two pumps is all it took?

[RogerC 136]

Just now, KMD88 said:

Hi Roger. Choke is set and works fine. So no matter when you were starting the motor (cold or otherwise) two pumps is all it took?

yup, that was about 18 years ago but I drove it to work everyday year round and I don't recall ever having a problem with it.

[barnett468 418]

I would forget what the mechanic said and check the timing and carb yourself. A mechanic is rarely a tuner.

[Caseyrhe 650]

I’m having a similar issue with both my 82 and 70 with the Holley 600. Next time after it been sitting remove the air cleaner, hand throttle and see if the squirters are squirting. Once I engage the pump lever further, it’s begins to squirt. Fires right up after that.  I believe it’s the gas these days

[barnett468 418]

10 minutes ago, Caseyrhe said:

I’m having a similar issue with both my 82 and 70 with the Holley 600. Next time after it been sitting remove the air cleaner, hand throttle and see if the squirters are squirting. Once I engage the pump lever further, it’s begins to squirt. Fires right up after that.  I believe it’s the gas these days

Your accelerator pump diaphragm may be dried up or needs adjusting if there is free[play in it.

[Caseyrhe 650]

Prob needs some adjusting, both carbs are less than a year old. 

[JET 445 43]

[1969_Mach1 333]

Your 600 CFM Holley likely has an electric choke.  They work good, but, one drawback of electric chokes is they cool and reset faster than the engine cools.  After sitting an hour or two the choke might be closed again, then plus some pumping of the throttle causes the engine to flood.  One other possibility is when sitting for an hour or two with a hot engine, the fuel in the carb bowls heats up, percolates and drips into the motor through the circuits inside the carb, thus, flooding the motor.  One of those thick heat insulating gaskets or a phenolic carb spacer will usually stop that from occurring.  The latter situation is more common when aluminum intakes are installed and the heat crossover passage is not blocked.  Another much less common cause of flooding with Holley carbs when the motor sits is leaking metering block gaskets in the carburetor.

[KMD88 2]

3 hours ago, 1969_Mach1 said:

Your 600 CFM Holley likely has an electric choke.  They work good, but, one drawback of electric chokes is they cool and reset faster than the engine cools.  After sitting an hour or two the choke might be closed again, then plus some pumping of the throttle causes the engine to flood.  One other possibility is when sitting for an hour or two with a hot engine, the fuel in the carb bowls heats up, percolates and drips into the motor through the circuits inside the carb, thus, flooding the motor.  One of those thick heat insulating gaskets or a phenolic carb spacer will usually stop that from occurring.  The latter situation is more common when aluminum intakes are installed and the heat crossover passage is not blocked.  Another much less common cause of flooding with Holley carbs when the motor sits is leaking metering block gaskets in the carburetor.

You may be onto something here. There was one day where temps were unusually high. After about an hour, I started the car and it acted as if it was flooded. Had to put my foot down on the pedal and crank until it started running.

Also, we found the throttle cable retainer was broken at the carburetor bracket, so that's being replaced as well. Could that have contributed at all? 

[barnett468 418]

3 hours ago, KMD88 said:

1. You may be onto something here. There was one day where temps were unusually high. After about an hour, I started the car and it acted as if it was flooded. Had to put my foot down on the pedal and crank until it started running.

2. Also, we found the throttle cable retainer was broken at the carburetor bracket, so that's being replaced as well. Could that have contributed at all? 

1. This is why  I said I would forget what the mechanic said and check the carb and timing myself.

Put some paper towels under the right front side of the carb.

Start the car then turn it off.

Remove the screw on the side of the float bowl. If gas dribbles out onto the paper towels, the gas/float level is too high.

Set the gas level so it is just a little below the inspection hole as soon as you turn the engine off.

The screw should be installed when the engine is running.

 

2. Not likely

 

 

 

[KMD88 2]

Thanks everyone for your help. Got the car back over the weekend, and did some experiments.

Cold Start (sitting for a day or so) – 2 Pumps. Crank.

Warm Start (Within half an hour) - Half a pump.

Mid-Way (about an hour or more) – crank and press down about 3/4*

By the way, is there anything wrong with cranking, then adding gas? I know it's supposed to be reversed, but was just curious if it makes a difference.

Thanks!

 

[1969_Mach1 333]

Either way is fine.  When I'm not certain if or how much to pump the throttle I will start cranking first.

[KMD88 2]

18 minutes ago, 1969_Mach1 said:

Either way is fine.  When I'm not certain if or how much to pump the throttle I will start cranking first.

Thanks 1969_Mach1.

[barnett468 418]

3 hours ago, KMD88 said:

Thanks everyone for your help. Got the car back over the weekend, and did some experiments.

Cold Start (sitting for a day or so) – 2 Pumps. Crank.

Warm Start (Within half an hour) - Half a pump.

Mid-Way (about an hour or more) – crank and press down about 3/4*

By the way, is there anything wrong with cranking, then adding gas? I know it's supposed to be reversed, but was just curious if it makes a difference.

Thanks!

 

Why didn't you also check the gas level in the carb?

[GypsyR 32]

Part of this is why some people say old vehicles have "personality", you have to get to know what they "like" and "don't like". Sounds like you are on the way.

Another thought, when I feel like the engine is still pretty hot after stopping at the store or for a quick lunch I will take care not to tough the accelerator pedal at all, just turn the key. Most of the time it works best for me. If not then I will put the pedal down pretty far and hold it and continue cranking it like that. Three of my vehicles like this but a fourth does better if the throttle is cracked open just a bit.