Hard hot starting.....what causes it?

Hard hot starting.....what causes it?

Duane K Estill (Corinth, Mississippi)
Duane K Estill (Corinth, Mississippi)

June 20th, 2008, 3:58 pm #1

I'm starting to notice with the '79 that it's harder to start when hot, grinds on and on. I've seen this mentioned before but can't remember the issue. 79 with dual 40 Webers, race cam, header, etc. Carbs are a little dribbly (accelator pump diaphrams) but work okay.
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Joined: August 29th, 2005, 1:53 am

June 20th, 2008, 4:05 pm #2

Duane,

The issue is the same as any carb's X. The heat from the exhaust manifold/header rises and boils the fuel in the float bowls of the carbs.

I solved this problem by fabricating and installing a heat sheild between the headers and carbs. Removing the rain tray helps this issue as it prevents the heat from being trapped under the engine lid.

Steve
1x5
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Joined: September 7th, 2005, 4:37 pm

June 20th, 2008, 8:13 pm #3

I'm starting to notice with the '79 that it's harder to start when hot, grinds on and on. I've seen this mentioned before but can't remember the issue. 79 with dual 40 Webers, race cam, header, etc. Carbs are a little dribbly (accelator pump diaphrams) but work okay.
Probably not with the dual DCNF's, huh?


Paul Valente
Berkley, Michigan
USA

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Duane K Estill (Corinth, Mississippi)
Duane K Estill (Corinth, Mississippi)

June 20th, 2008, 8:27 pm #4

,............
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Pat Higgnbotham
Pat Higgnbotham

June 20th, 2008, 9:47 pm #5

Probably not with the dual DCNF's, huh?


Paul Valente
Berkley, Michigan
USA
react to the fan operating properly but in my 84 FI car it made a dramatic difference.
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Joined: December 21st, 2004, 3:04 am

June 21st, 2008, 5:47 am #6


... when the engine is OFF. 

I understand on the FI cars, they run all the time.

(My experience with "Hard Starting" has only been after the carb fan has been running all day in the parking lot... starting by itself probably around 2pm, and then running my battery flat!  Always fun standing there with jumpers or pushing the car in the p-lot.  After the second time... I ripped it out back in '84... never looked back!)

I feel the REAL problem is the raintray strangling the venting action of the deck lid.  I just ran around town here today in 105 degree heat, car stayed at 185 - 190 and restarted immediately everytime.

Ya might try it... you can always rivet it back in place if ya don't.


My best,



Tony
Black Tooth and me... since 1983!
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Joined: September 7th, 2005, 4:37 pm

June 21st, 2008, 12:04 pm #7

Since you didn't see any benefit from your malfunctioning POS carb fan, nobody needs a properly functioning one either. Brilliant! All the other guys that said it made a dramatic difference are all wrong and you are right because your sample size of ONE proves your theory. You have won me over! I'm going out to take mine off rigth now! It only runs "when the engine is OFF" anyhow. How's that going to help a hard starting? This further proves your point! Quod erat demonstrandum!



You're the King of the Forum, Tony! I will respectfully leave it to you without my further interruptions and switch over to the Fiat Forum.

Bye all!

Paul Valente
Berkley, Michigan
USA

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Joined: August 7th, 2006, 3:12 pm

June 21st, 2008, 3:35 pm #8

... when the engine is OFF.&nbsp;

I understand on the FI cars, they run all the time.

(My experience with "Hard Starting" has only been after the carb fan has been running all day in the parking lot... starting by itself probably around 2pm, and then running my battery flat!&nbsp; Always fun standing there with jumpers or pushing the car in the p-lot.&nbsp; After the second time... I ripped it out back in '84... never looked back!)

I feel the REAL problem is the raintray strangling the venting action of the deck lid.&nbsp; I just ran around town here today in 105 degree heat, car stayed at 185 - 190 and restarted immediately everytime.

Ya might try it... you can always rivet it back in place if ya don't.


My best,



Tony
Black Tooth and me... since 1983!
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...and they're action is rather amusing as the Italian engineers that came up with that design obviously didn't understand the principle of hysteresis... when I turn the car off the fan will cycle fairly rapidly for about 10 minutes as things cool down...

Jim W. (in the Northeast)
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Joined: December 18th, 2004, 1:50 am

June 22nd, 2008, 12:35 am #9

I'm starting to notice with the '79 that it's harder to start when hot, grinds on and on. I've seen this mentioned before but can't remember the issue. 79 with dual 40 Webers, race cam, header, etc. Carbs are a little dribbly (accelator pump diaphrams) but work okay.
Since I had this problem with my car new in 79 and with a single DCNF Weber I did the following.

Carb cooling fan can only run with the Key in the on position, this will never let the battery drain down to nothing.

Add an electric fuel pump. I have my electric feeding the stock Fiat mechanical pump.

Install a Tee fitting in the fuel line just infront of the Carb bowl this will let hot fuel in the lines circulate back to the tank. The Tee must have a restriction orface in it to allow the pressure to build at the carb bowls.

Starting sequence when engine is hot. Turn on ignition key, listen for carb cooling fan, if it is running turn on electric fuel pump as well for 1 minute. This circulates the fuel from the tank and allows the carb cooling fan to cool the carbs. Next start engine and let idle for 1 minute. If you press on the gas pedal and the engine snuffs then you wait and try this all over again.

If you have headers you need a heat shield, I made mine from 2 sheets of alum. spaced about 3/16" apart to force the hot air to rise away from the carb.

Hope this helps. Question? Ask.

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Joined: June 16th, 2004, 3:48 am

June 22nd, 2008, 2:31 am #10

I'm starting to notice with the '79 that it's harder to start when hot, grinds on and on. I've seen this mentioned before but can't remember the issue. 79 with dual 40 Webers, race cam, header, etc. Carbs are a little dribbly (accelator pump diaphrams) but work okay.
Many years ago like perhaps 20 Bayless used to sell a plastic spacer. This mounted at the base of the carb and isolated it from metal to metal contact. It was about 3/8 in. thick, sounded like it would really work. This was the reason it was sold to avoid vapor lock. I never did get around to installing it however.
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