key4

iTrader: (10)

I got a pro systems carb for my car and when its real cold outside its really hard to start. Its a race version so it has no choke. Im really new at carbs and wondering is theres a way to make it start a little easier. Never really figured the carb out anyhow. When its warm it starts fine but seems like to me it takes a little while for it will idle on its on without going dead. Is there anything I can do or is that just a race type carb?

ZONES89RS

iTrader: (25)

Back off the primary idle circuit screws about 1 to 1.5 turns on the primaries, that will allow the idle mix to richen up allowing easier starts, they wont be perfect but with some time and tuning, it will not be bad. It is how mine are, they will start in the cold and do not take ling to idle on their own.

key4

iTrader: (10)

Sorry man I so new to carbs. So do I back them off from where they are now or do I screw them all the way in and then back off 1 to 1.5 turn? Ok is the primary the front two and the secondary are the back two? Im not 100 percent sure but I think I got my timing pretty close. I will make sure tho. Thanks

brngrhd

yes your fronts are primary and the rears are secondaries..... Id say 1-1.5 turns from all the way in. if you can live with the cold starts they usually like .75 out .1-1.5 is usually a bit rich richer will make it easier on cold starts.

S10xGN

iTrader: (11)

key4, I've got the same problem and I've just been living with it. I've got to say, those idle screws are very sensitive! I can make a 1/8 turn adjustment and change the AFR over 2 full points so be careful doing this. The original setting of 1.5 turns out gave me a 9.5:1 AFR and within minutes had fouled every plug so bad it would not restart at all.

I've thought about making a "cold start solenoid" to bleed in some air and raise the idle speed. I found some 12V air horn solenoids that would work using a Holley jet in it for a restriction orifice to control the amount of air. Still considering the wiring side of it...

xpndbl3

iTrader: (23)

Personally I'd rather a good running warm motor than a good running cold one and too rich warm motor. You have no choke, tap the pedal until it catches and builds heat on its own. Zones says 1 turn more than what you have now is a big change, i'd be looking into a 1/8th turn to 1/4 turn at most.

Pop N Wood

iTrader: (1)

I have to agree with the others, with my carb 1 1/2 turns will be massively rich. Mine sit a little over 1/2 turn for a 15:1 idle mixture.

Also like said above just keep pumping the pedal and reving the motor till it heats up.

The alternative is to switch to a choke carb in the cold months.

key4

iTrader: (10)

Ok guys thanks, I will play with the idle screw alittle but thats what I usually do is just pump the pedal till its warm. Its just real hard to get it to start when its cold. I was just wondering if this is a common problem or not.

ZONES89RS

iTrader: (25)

With no choke, it is very common, life of a race ready carb. Every carb is different, so the amount you back off will be determined by your particular carb. I have 4 corner idle and i think i run 1 turn out on the primaries and 3/4 out on the secondaries if i remember right.

key4

iTrader: (10)

Got one more question. On a cold start would it start better with less timing or more timing?

xpndbl3

iTrader: (23)

should fire up at any timing quickly. Mine is pump the pedal once and turn the key, 12 degrees timing until 500rpm, then from there it jumps up to 29, then 34 at 2000

key4

iTrader: (10)

Thanks, yea I think mine is too high at when the key is on till 500rpms. Also around what fuel pressure are you guys at? I got mine set at 8 but when I when I first start the fuel pump its around 9 or so but it falls back down to 8when it warms up.

ZONES89RS

iTrader: (25)

I run 6.5, 8 is too much man, especially 9.

3pedals

iTrader: (3)

yeah, when fuel pressure gets up around 7psi, your on the verge of forcing the needle/seat open just with your fuel pressure. you dont want that to happen!!!
I run mine as low as 5.5psi.

key4

iTrader: (10)

yea I really trying to figure the whole carb and fuel pressure thing out. I have a areomotive a1000 and a bypass regulator. I have the gauge coming off the regulator and really dont think its working right. Reason I say that is when I adjust the fuel pressure down it just wont go any lower than 7.5. I can almost screw the adjuster all the way out of the regulator and still reads around 7.5. I really think I need a new gauge.

xpndbl3

iTrader: (23)

run a quality gauge not one of those 1.5" diameter cheapies. Also you need to kill power to the pump and turn it back on to recheck fuel pressure everytime you make an adjustment. If it wont drop enough at idle then you have a return line restriction somewhere or the line needs to be larger.

tennerv8

iTrader: (7)

I have an L92 headed 6.0 with a proform dp 750 carb with no choke or choke tower. It will fire at any temp so far. I fired it up at zero degrees F. a few weeks ago. I did have to pump it until raw fuel damn near ran out the exhaust.

Pop N Wood

iTrader: (1)

Or a bigger return line. that is exactly how you are suppose to check the return line, by fully opening the regulator and measuring the back pressure. The fact your back pressure is so high says your return line is either too small for that big pump or you have a restriction somewhere.

DMMizell

iTrader: (1)

May not be the carb at all.
Try to start using a jump box to improve cranking voltage.
The MSD needs 10 volts to fire the engine.
My car would not cold start below 50 degrees F with an Odyssey 680 race battery. Put the jump box on and it would fire up , once the oil was warm it would be ok the rest of the day.

Dave

hifi875

iTrader: (2)

electric choke.