carb question - warm hard starts

Hack · May 31, 2006

It's my '83 5.0 4 barrel which is another forum I know, but there are carb experts that I know and trust here, so..

My '83 Mustang starts hard when warm. It's like the car doesn't get enough fuel. Today I ended up pouring some gas down the carb and then it started. I had to keep my foot on the gas to keep it running at that point, though.

It starts fine cold, but if I give the gas a quick bump to move it off the fast idle cam, it will die. It's like the choke should stay on but doesn't. It seems to me that the same situation is occurring when the car is warm. I should be able to get the choke on, but no go.

This car has an electric choke and it's the factory Ford 4 barrel built by Holley.

What should I do?

D.Hearne · May 31, 2006

Is the choke butterfly opening after it's warm ?

pabear89 · May 31, 2006

Just a guess from your discription,
A possable internal leak is flooding the intake.

Wilth the engine up to operating temp, remove the air cleaner and shut engine down.
Watch closely the carb air horn areas for a light wisp of steam looking smoke coming up from it.
It is a sure sign of fuel leaking into the intake.

PB

Hack · Jun 2, 2006

D.Hearne said:
Is the choke butterfly opening after it's warm ?

I checked this last night.

I walked up to the car and measured the opening at about 0.250". This is how far it was open when good and hot after I shut it down last time.

I pumped the throttle once to set the choke, and the opening was about 1/16" or maybe about 0.050". I started the car with no problem.

I let the car idle for a few minutes, by now it was idling at 2500 rpm. Pretty fast! I blipped the throttle and it tried to idle at about 700 rpm and then died. I checked the butterfly opening at this point at it was about 0.170"

I tried briefly to restart the car, but this is the point where I would have to pour some gas down the carb to get it to go.

Hack · Jun 2, 2006

pabear89 said:
Just a guess from your discription,
A possable internal leak is flooding the intake.

Wilth the engine up to operating temp, remove the air cleaner and shut engine down.
Watch closely the carb air horn areas for a light wisp of steam looking smoke coming up from it.
It is a sure sign of fuel leaking into the intake.

PB

I have never noticed this, but I will check tonight. I don't think the car is flooding, because when I pump the gas it will almost fire. If I don't touch the gas it doesn't get quite as close to starting. Last night after a few minutes of running in 80 degree temperature, it didn't steam/smoke.

The car works great when it's hot. It's just when it's slightly warm but not hot or completely warmed up that the problem comes in.

pabear89 · Jun 2, 2006

Working from your prev posts......
The choke is closing too far and setting the fast idle screw high up on the choke cam, thats what causing it to race at high rpm.

the slightly warm hard start problem sounds like the airbleed holes are plugged, use some carb cleaner to flush them out.

With the engine on its cold start running with choke set to keep rpms up,
manually open the choke plate and spray directly down into them.
they are the four little dimple spots toward the front of the air horn on eather side of the center piece....damn it's early and I can't think of the name of it.

But being plugged will not allow fuel to be drawn at low vac.

PB

Hack · Jun 2, 2006

pabear89 said:
Working from your prev posts......
The choke is closing too far and setting the fast idle screw high up on the choke cam, thats what causing it to race at high rpm.

the slightly warm hard start problem sounds like the airbleed holes are plugged, use some carb cleaner to flush them out.

With the engine on its cold start running with choke set to keep rpms up,
manually open the choke plate and spray directly down into them.
they are the four little dimple spots toward the front of the air horn on eather side of the center piece....damn it's early and I can't think of the name of it.

But being plugged will not allow fuel to be drawn at low vac.

PB

AAAAHHH, thanks PB!!

Great explanation. I cleaned the carb as you explained. Then I blipped the throttle and it dropped down to 1500 rpm. Much better! The car kept running.

I shut it off and it started up again with no problem. You nailed it. I'll see if I can fix the choke issue later.

Thanks again.

carb question - warm hard starts

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