truck does not like to run in the cold

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85gtr720
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truck does not like to run in the cold

Postby 85gtr720 » Thu Jan 22, 2009 11:25 am

i have a 85 720 with the z24 motor and any time it get below 40 degrees it starts to run like crap it idol's fine but when you try and drive it spits and sputters and you are stuck going around 25mph i can tell if it is fuel or spark problem but i am tired of driving it because of the bucking it does when you try to accelerate. when it warm there is no real problem accept a lil cut out at higher rpms please help me


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PEZi
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Re: truck does not like to run in the cold (85gtr720)

Postby PEZi » Thu Jan 22, 2009 11:44 am

mine actually did this for a while when i first got it.... the biggest problem is it could be a wide number of things...

mine in particular was a bad distributor cap... wires... batt etc

there was also major problems in the vacuum hoses

and don't forget the clogged fuel filter

my best advice is to check everything and if all of this fails just remember its carbureted and that don't do so hot in the winter... you may need to tweek the flow within

keep us posted on anything you figure out

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PEZi
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Re: truck does not like to run in the cold (PEZi303)

Postby PEZi » Thu Jan 22, 2009 11:45 am

another point i forgot to mention.... is the engine itself warming up properly??? cause when its not warm it will run like this and just fixing the warming up issue may solve it

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85gtr720
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Re: truck does not like to run in the cold (PEZi303)

Postby 85gtr720 » Thu Jan 22, 2009 1:20 pm

it warms up normally i have checked vac hoses and changed filter and cap and rotor are fine

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Re: truck does not like to run in the cold (85gtr720)

Postby PEZi » Thu Jan 22, 2009 5:27 pm

check to make sure it isn't something too extreme... check for spark in all the plugs while its cold. check the fuel pump for flow... clean the carb etc. depending on miles and how hard the truck has been driven it may be time to rebuild the carb. this is of course the far extreme tho.

the symptoms are the exact same that i had... they didn't come up until it got cold out just like yours... and mine was in the spark

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Postby NTEC » Sat Jan 24, 2009 8:50 pm

I have an 85 720 that does this too. I don't drive the truck much, but it will remind me that I haven't fixed the problem when the temp drops and I drive it. It will act like it starves for gas, and if you push it it will just about shut down. I have not been able to get under the hood and see if the bowl is full or not while this is happening. I suspect it has something to do with the EVAP system for some reason, but I does not do this all the time and When I get into the truck to do something I generally have more important stuff to do than hunting for the problem. It will usually go away if I stop and let it idle for a couple of minutes and finish warming up. It does not do this if I let it full warm up before I leave with it. I have also known of two other trucks doing the same thing and I don't know if anyone has found the cause yet.

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Re: (NTEC)

Postby PEZi » Sat Jan 24, 2009 11:03 pm

NTEC wrote: It will usually go away if I stop and let it idle for a couple of minutes and finish warming up. It does not do this if I let it full warm up before I leave with it
this warming up process has always served me well

i usually warm it up for 10 minutes when it is below freezing and no issues come about

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85gtr720
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Re: (PEZi303)

Postby 85gtr720 » Sun Jan 25, 2009 3:32 pm

i usually let it warm up to temp before i drive it there is times when ill let is idle form 30min to an hour and it still acts up on me

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Re: (85gtr720)

Postby PEZi » Sun Jan 25, 2009 8:50 pm

the hardest part of any fix project is the diagnosing

by the sounds... you're not getting fuel... but the trick is figuring out why and that can be a b*tch to figure out

if you are indeed still running the stock fuel pump... its definitely time for a change and if it works it works... if not you fixed somethin that was soon to go out anyway so you're not at a loss

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85gtr720
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Re: (PEZi303)

Postby 85gtr720 » Mon Feb 09, 2009 2:03 pm

i just tried putting the fuel pump that i had on my 73 dodge charger big block and the pick up still cuts out i changed the cap and rotor and checked for vac leaks

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Re: (85gtr720)

Postby PEZi » Mon Feb 09, 2009 2:22 pm

it must be something in the carb if none of this is working then... the carbs on these do go bad after this many years

if i were you i'd save up for a weber carb or maybe some side drafts... even if that doesn't help you'll have the whole thing torn apart to find any other problems anyway

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85gtr720
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Re: (PEZi303)

Postby 85gtr720 » Mon Feb 09, 2009 2:25 pm

what is the weber part numb for the 720

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Re: (85gtr720)

Postby PEZi » Mon Feb 09, 2009 7:53 pm

i'm not a 100% sure but it looks like 3236

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Re: (85gtr720)

Postby phlebmaster » Tue Feb 10, 2009 4:46 am

85gtr720 wrote:what is the weber part numb for the 720
The Weber 32/36 is the standard carb replacement. The only part you will need to investigate is the adapter.


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