Hard start in cooler weather? (1 Viewer)

[71FFJ40]

I know how everyone likes the same questions beat to death so here goes.........

This has been an ongoing issue for the last few years.

1971 Stock F that has been desmogged-not recently
1971 Stock Aisin that has been rebuilt-not recently
Electronic ignition.
Gear reduction Starter.
Plenty of cranking amperage/voltage.


- The truck starts instantly when outdoor air temp is approximately 50f or above.No choke or pumping pedal required.

-As soon as the morning temps start dipping into the low 40's the truck is very hard to start-sometimes it won't start until air temp rises into the upper 40's and above later in the morning/day.

-Seems to be getting plenty of fuel-sight glass always approx. half full.Can smell gas after cranking/pumping pedal.

-Full,half,partial choke-doesn't make a difference.
-Pump the pedal and hold it floored while cranking-doesn't make a difference (Need to do this for hot starts).
-No vac. leaks-draws about 20-22hg consistently
-Valves are adjusted correctly.
-Once it starts it runs like a champ.
-Carb is adjusted as per FSM.

Any ideas?

 

[1911]

First thing I would check is the choke linkage; ascertain that the choke is working as intended.

 

[John McVicker]

^^^
This

 

[FJ40Jim]

Verify that the accel pump gives a good squirt for each of the 3-4 times the pedal is pumped before attempting to start.

 

[71FFJ40]

Appreciate the input.
All of the above has been checked and verified......more than once...while the air cleaner cover is off.

Choke is working correctly and closing completely.
Accelerator pump is functioning correctly.Nice steady spray.
I am wondering if there is excessive flow of fuel being dumped into the carb?

This issue seems to be directly related to the outside air temperature.Extremely frustrating.

 

[71FFJ40]

Just tried to start the truck again.No dice.Current air temp is 55f.

I had the air cleaner cover off.I'm assuming I flooded the carb with earlier starting attempts.
The fuel shot up from the carb like a geyser when I tried cranking after 3 pumps with the pedal to the floor?

 

[Living in the Past]

Didn't see where you checked the timing. Has that been done?

 

[SteveH]

If you think you may be flooding the engine before it starts, do this:

Start cranking - keep cranking while doing the next two steps:

• Pull out the choke fully - see if it starts
• Pump the gas with the choke engaged, while still cranking - see if it starts

This gives the engine a chance to get started before you (potentially) drown it.

Also, like today (when it didn't start) immediately pull a couple spark plugs and see if they are soaking wet with gas. If so, then lack of fuel is not the issue.


Steve

 

[71FFJ40]

Didn't see where you checked the timing. Has that been done?

Yes.At the time of the last valve adjustment about 2 months ago.

 

[71FFJ40]

If you think you may be flooding the engine before it starts, do this:

Start cranking - keep cranking while doing the next two steps:

• Pull out the choke fully - see if it starts
• Pump the gas with the choke engaged, while still cranking - see if it starts

This gives the engine a chance to get started before you (potentially) drown it.

Also, like today (when it didn't start) immediately pull a couple spark plugs and see if they are soaking wet with gas. If so, then lack of fuel is not the issue.


Steve

I've tried every method as far as full choke-no pump,full choke-pumping,half choke,1/4 choke,3/4 choke,no choke while pumping,etc.
I have pulled plugs and found them to be wet in the past when this has happened.I don't feel it is lack of fuel?

Here is the kicker.I just tried again before typing this.The curent air temp is now 57f.I pumped the pedal three times,floored it,cranked the engine,it sputtered,I feathered the pedal and voila' it's alive and idling perfectly and purring like a kitten as if the cold start issue never happens??
I turn it off.Barely turn the key to start and it fires right up.Over and over without even the slightest hesitation.

 

[brian]

i'm not understanding the holding the throttle fully open while cranking part?....that sorta reduces or even eliminates the effect of choking of it.

 

[71FFJ40]

i'm not understanding the holding the throttle fully open while cranking part?....that sorta reduces or even eliminates the effect of choking of it.

When my engine has been running for a bit-let's say at least a 1/2 hr of highway speed driving-and I then shut it off-and head in to a store for 10 minutes-I need to pump the pedal 2 or 3 times and then hold the pedal to the floor to start the engine again.This is typical for my truck-air temp not a factor.Hot,warm,cold doesn't matter.
This same method usually works when the truck is cold (but the air temp is above 50f) if It doesn't start on the first try-no pedal-just turning the key- which is rare.

I don't think I have ever had it start by applying full choke and then pumping or flooring the pedal at the same time while cranking.Just full choke and cranking yes-but not choke and pump.

 

[Pin_Head]

i'm not understanding the holding the throttle fully open while cranking part?....that sorta reduces or even eliminates the effect of choking of it.

Me neither. With the choke closed and the throttle open, you are going to pull a lot of fuel out of the main nozzle flooding the engine.

At 55F, I would give it one pump, close the choke 3/4 and hit the key with my foot off the throttle.

 

[B y r o n]

Have you tried to start it without doing any pumping of the throttle using just the choke?

 

[71FFJ40]

Have you tried to start it without doing any pumping of the throttle using just the choke?

Yes.If the outside air temp is Below 50f-no go.
Have also tried full choke only-no pumping when the temps are above 55 or so-fires right up.

 

[brian]

Too much pumping and holding

 

[71FFJ40]

Too much pumping and holding

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I agree and have read those same pages.
The method described for ambient temps between 32 & 70f doesn't work for me-at least not between 32-55f.
Anything above 55 or so and no choke or pedal pumping required.The truck almost always fires up immediately with usually just a single flick of the key.
For some reason this carburetor does not seem to like cool temps below what is becoming a frustrating threshold.

 

[B y r o n]

I think the problem could exist in your electronic ignition.

I had a 75 Camaro and it developed a problem that was 180 from your problem, it quit running when it got hot. The problem was eventually traced to the module inside the distributor. When it got warm a circuit trace would open and the car would die. As soon as the circuit cooled it would run fine again.

In your case I believe that a circuit connection is being broken when it is cold but regains connectivity once it warms. Not sure how to track it down but probably worth looking into.

 

[Skreddy]

To track down if it’s the ignition when cold, use a hair dryer or heat gun on the distributor with cap removed to warm it up a bit, pop the cap on real quick and try starting it.
Have you verified jetting is correct for your location? On a lot of motorcycles I’ve helped people sort out, they always have some ritual to go through to get it to start. They are usually way overjetted, incorrect accel pump setting or timing issues. I’ve long been of the mindset that properly tuned, almost any old carbed motor should start with a quick throttle blip, some degree of choke (depending on temp) and that’s it.

 

[ICD FJ40]

Too much pumping and holding

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Learned a new word. "Grobe": a rough calculation, or fishnet hose