Carburetor questions - Cold Start

"Akio Ohtori - RIP Oppo" (akioohtori) 01/31/2019 at 12:10 • Filed to: project golf ball

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So I am new to this whole “trying to ‘ daily drive’ a carbureted car” thing. How hard should this thing be to start? It was 18F (yes, I know, very balmy Chicago Oppos) this morning, the car had been sitting for 36 hours, and here was my starting sequence: (Automatic choke, fyi)

Couple slow cranks to top off the bowl (probably not needed, but hey we’re trying new things!)

Pump the gas five times

Crank, catch, instantly die

Repeat 2&3 about 4 times

Eventually start at 1100 RPM and sputter its way up to starting RPM of 2000. (Settles at high idle after I blip the throttle)

An above freezing cold start usually looks like:

Pump the gas 3-4 times

Crank, catch, and die after a half second ( about 50% of the time, otherwise skip to 4 )

Pump gas 1-3 times

Crank, catch, run at 2000 RPM until I blip the throttle, when it settles to high idle (~1,100)

Does that sound about right? Or should I be adjusting something? The thing hot starts almost too well.

My bird IS the word > Akio Ohtori - RIP Oppo 01/31/2019 at 12:12

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You forgot the “dump an entire can of starting fluid, curse, kick the car, curse again” step

gmctavish needs more space > Akio Ohtori - RIP Oppo 01/31/2019 at 12:15

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The weber on the Raider will crank for a while if it’s pretty cold, but usually go straight to the high idle and not need started again. If started recently, but cold, it starts on the first or second turn over. If it’s hot, however, it cranks a ton, and the throttle often needs feathered to get it to start.

I haven’t taken it to my mechanic yet for him to tune it better than I can, soo...yeah.

BigBlock440 > Akio Ohtori - RIP Oppo 01/31/2019 at 12:17

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Play around with different things until you find something that works better than your previous method, there’s no universal SOP, it depends on the vehicle.

Berang > Akio Ohtori - RIP Oppo 01/31/2019 at 12:18

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Find the user manual? My old 82 Toyota, I believe the procedure was to pump the pedal twice, and on the second pump to push it to the floor - which set the high idle cam on the carb. Once started you’d let it idle for about 30 seconds to a minute and then stomp on the pedal again to take it off the high idle cam. On cold Colorado morning it sometimes took two or three tries to get it to fire up.

My Saab would use the same basic procedure, if it still had the factory carb.

lone_liberal > Akio Ohtori - RIP Oppo 01/31/2019 at 12:18

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You may need to adjust the choke. The plate might be either not closing far enough or closing too far. The last part about it idling fast until you blip the throttle is pretty normal. The process for my Camaro after it has sat for a while is crank, pump 3 or 4 times, crank, starts with high idle, blip throttle, settles at fast idle until warm then goes to normal idle.

Highlander-Datsuns are Forever > Akio Ohtori - RIP Oppo 01/31/2019 at 12:19

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I usually go:

1. pump gas 3-5 times

2. turn ignition on and leave on for 5-10 seconds to prime fuel pump

3. crank without touching gas pedal

4. after 4-5 seconds of turn overs start feathering gas pedal

5. go of fuck I’ve floo ded it again.

DipodomysDeserti > Akio Ohtori - RIP Oppo 01/31/2019 at 12:20

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Doesn’t sound too bad. If your F/A is already correct when warm, I wouldn’t screw with trying to get it to start smoother when cold. As long as it’s running smooth when warm I’d leave it.

Akio Ohtori - RIP Oppo > Highlander-Datsuns are Forever 01/31/2019 at 12:24

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go of fuck I’ve flooded it again

I giggled.

Mechanical fuel pump, so step 2 wouldn’t work. I’ve also found with the Weber touching the gas (outside of pre-start pumping) ruins everything. I think it messes with the choke/high idle settings.

Akio Ohtori - RIP Oppo > DipodomysDeserti 01/31/2019 at 12:25

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Cool.  Yeah it is a little hesitant until it is warm, but I think it runs great fully warmed up.

adamftw > lone_liberal 01/31/2019 at 12:25

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This. Doesn’t sound too bad but there may be a choke adjustment OP can do to make it better.

deekster_caddy > My bird IS the word 01/31/2019 at 12:28

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In general, it works like this:

1) pump the gas pedal x times (usually twice). This shoots gas from the fuel bowl into the intake and sets the choke.

2) crank the engine. If really cold you may need to add 1/8 to 1/4 throttle to help it start.

Troubleshooting... well this is where it gets fun.

Is there fuel in the bowl? With the air cleaner lid off, you should be able to see gas squirt from the accelerator pump into the carb base. Does the bowl hold fuel overnight? If not, something is leaking... then you need to fill the bowl first. Mechanical fuel pump means crank it over a few times. Elec fuel pump means turn the key on and off a few times.

Is the choke closing all the way? Mechanical chokes have a bi-thermal spring that should close the choke when cold. Sometimes something is in the way... Electric chokes - be careful! If you leave the key on for a while, the electricity warming the spring may cause the choke to start to open, and you need it closed if it’s really cold out!

Once it starts, there should be something akin to a ‘choke pull off’ - a vacuum actuated solenoid to crack the choke open a little bit, overriding the spring trying to hold it closed. It needs to breathe...

High idle - when the choke is closed there should be an accomp anying high idle step, whether it’s a solenoid or physical steps is up to the design of the carb...

These are the basics. If you pump too much and flood it, it’s going to be a bitch to start. If you don’t give it enough gas, it will crank a little longer but should still fire. Most common issue is people pumping away and flooding it.

I’ve driven carbeurated cars through some really frickin cold weather and thanks to some attention to what’s going on I’ve always been able to start them even in frigid cold. These basics are not specific to any particular carb... Good luck!

RamblinRover Luxury-Yacht > Akio Ohtori - RIP Oppo 01/31/2019 at 12:30

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My car has been starting near-instantly with about half pedal in around 25F weather, and this morning only required one false start, two pumps, and away.

Of course, I know for a fact that the automatic choke is set properly because I did it.

benjrblant > Akio Ohtori - RIP Oppo 01/31/2019 at 12:31

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no mention of choke?

and with a carb, you should let the engine warm up before attempting to drive as loading the engine usually results in stalling when it’s too cold. carbs cannot adjust for air temp/density very well.

edit: d’oh, i see automatic choke now. sorry.

vicali > My bird IS the word 01/31/2019 at 12:31

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or the sit in the cold car cursing for 15 minutes while it un- floods..

Akio Ohtori - RIP Oppo > benjrblant 01/31/2019 at 12:35

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It is an automatic choke. I haven’t adjusted it because, aside from really cold mornings, it seems to do its job.  Keeping an eye on it though.

And yeah, I let it sit for a few while I scrape or move cars, then take it easy until I get fully warm. Having driven injected cars my whole life I’m just not sure what to expect out of a carburetor haha.

Akio Ohtori - RIP Oppo > RamblinRover Luxury-Yacht 01/31/2019 at 12:36

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I’ve been avoiding adjusting the choke as it seems to be doing its job OK.  Also documentation from Weber is pretty spotty on how to actually go about that.

Audio Tachometer > Akio Ohtori - RIP Oppo 01/31/2019 at 12:37

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Electric chokes are pretty simple to adjust. usually the choke spring is held together with a few screws. Loosen them, don’t take them off, and twist the plastic body one way or another. On my Holley it has a little arrow pointing clockwise that says “lean”. Usually I twist it a little toward lean when it’s warm out and richen it when it’s cold.

benjrblant > Akio Ohtori - RIP Oppo 01/31/2019 at 12:37

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Yes, I re-read your post and noticed you mentioned that. A++ for reading comprehension this morning.

You should pull the air filter and dump a whole can of starter fluid in there. that’ll do ya.

Sovande > Akio Ohtori - RIP Oppo 01/31/2019 at 12:49

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Don”t pump the gas on a Weber> turn the key< listen for the fuel pump and then give the pedal two quick taps to set the choke> fire it up>
Should then be at high idle and will go back to regular idle speed with another tap of the pedal>

sorry for the punctuation< my keyboard has DEcided that it would like to operate under its own guidelines today

Sovande > Akio Ohtori - RIP Oppo 01/31/2019 at 12:53

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With a mechanical pump don’t turn the key, pump the gas a few times, turn the key on to power the choke, tap the pedal (or in my case two quick taps all the way to the floor) to set the choke and then t ur n it over.  Of all the carbs I have had, the Weber has had the easiest and most consistent choke.

Rusty Vandura - www.tinyurl.com/keepoppo > Akio Ohtori - RIP Oppo 01/31/2019 at 13:02

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Seems like many pumps. If it floods, holding the throttle wide open will suck only air and no fuel.

RamblinRover Luxury-Yacht > Akio Ohtori - RIP Oppo 01/31/2019 at 13:12

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I do have starting problems with the FERD from time to time, but they mostly have to do with vapor lock and a dodgy fuel pump I haven’t been arsed to replace yet. Car gets good and hot and sits, and the vapor from hot fuel line pushes fuel back through the pump... or if the fuel is just low-ish in the tank, the fuel creeps back into the tank as it sits and seems to drain some of the bowl, even. Then the automatic choke, being still warm, doesn’t help pull fuel through very well. CRANKCRANKCRANKCRANK VROOOHOOOMM .

If I keep the fuel topped off or it’s even remotely cool out it does fine.

Dash-doorhandle-6 cyl none the richer > Akio Ohtori - RIP Oppo 01/31/2019 at 13:29

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Seems about right.  Of 12 or so carbureted cars, 2 of them started like a dream in this sort of weather 85 yota and 65 straight six Pontiac.  All others required cold weather babying for about 40-60 seconds before running reliably on their own.  

Jake - Has Bad Luck So You Don't Have To > Akio Ohtori - RIP Oppo 01/31/2019 at 13:39

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Huh. Other than adjusting the choke slightly or making sure that it’s properly setting when it’s cold the start procedure with my cammed Chevy 350-powered Jaguar with an Edelbrock 4-barrel perched on it was:

Turn key to “on” to prime electric fuel pump

Floor gas pedal to set choke

It’d crank once, catch, die immediately

Crank it again and it’d start immediately and set into a high idle.

I drove it all through last winter with no issues.

Jake - Has Bad Luck So You Don't Have To > Berang 01/31/2019 at 13:39

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Electric choke Edelbrock on my Jaguar was the same way.

Tripper > Akio Ohtori - RIP Oppo 01/31/2019 at 13:50

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Also new to the carb life. Twin weber DCOE (sidedraft) carbs. must be auto choke because the manual choke is disconnected, or maybe it doesn’t need one because of the fuel pump? Anyway...

My cold start procedure:

Switch on the fuel pump and let it run until I hear it quiet down (maybe 5-8 seconds)

Pump gas pedal 5 times

Crank, catch, die 3 or 4 times

Crank while pumping gas until it starts

Keep it around 1000 until it’s warm, or it will stall.

DipodomysDeserti > Akio Ohtori - RIP Oppo 01/31/2019 at 13:51

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Yeah, the hesitation when cold is normal. I’ve got an extremely well tuned Edelbro ck carb on my truck, and even it will take  a bit of warmth before it is 100%. Same deal on my bike which I have tuned in really well. The coldest they’ve seen is low thirties.

Akio Ohtori - RIP Oppo > RamblinRover Luxury-Yacht 01/31/2019 at 14:09

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Ugh I’m having that problem with the Saab right now.  The check valve on the fuel pump is leaking, which is bleeding off pressure and preventing (what I am calling) a tepid start.  Cold: no problem.  Hot: no problem.  Mid-warm: open the hood and wait.

MiniGTI - now with XJ6 > Akio Ohtori - RIP Oppo 01/31/2019 at 23:59

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I like that - “ tepid start”

Our 2003 Civic had a weird problem where it would run super rough and almost stall about 2 minutes  after tepid starting it. Once it cleared up after a minute it was completely fine. And fine under all other conditions. Never figured it out and traded it for our first MINI which we loved.