1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

81 F100 4.9 Vacuum Routing

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Old 05-14-2010, 08:27 AM
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81 F100 4.9 Vacuum Routing

Hello Everyone,
This truck has been sitting for severa years, but due to financial restrictions I have been forced to return her to active duty. I have her up and running with no knocking or smoking, but I get mixed results with the idle everytime I start it. When I start her for the first time (cold) she wants to idle at about 2000rpm. If I hit the gas it brings down the idle, but will usualy die. Someone put a new carb a few years ago, but I don't think it is the same one that it originaly came with. I have taken some photos and I was hoping somebody could point out for sure where some of the hoses go, before I start trying to mess with any adjustment screws. I am pretty knoweldgable about the later model EFI ford trucks, but I know very little about carbs. Other than the cat, all of the factory emissions seems to be intact EGR, Air Pump, etc. I am not even sure which carb I have..


[IMG]file:///E:/DCIM/100KC613[/IMG]
 
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Old 05-14-2010, 10:06 AM
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photo does not appear. is there no sticker on the radiator support frame showing the vacuum routing diagram?
 
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Old 05-14-2010, 03:34 PM
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Sorry about that,
I do have the sticker, but I don't believe this is the same carb that the truck originaly came with. Can someone identify what carb I have? She doesn't want to idle when she is cold, but she usualy will once she gets warmed up. Even once she is warmed up she wants to die if you gun it a little and let off. I have no idea what kind of adjustments have been made to the carb, but I thought it would be wise to verify that all the vacuum connections are correct before I go tinkering with the carb. I am familiar with the late model EFI trucks, but have never really messed with a carb so I need some help on this one. I also understand most of the terminology and purpose of the vacuum/emission controls, but I need to know where the need to get their vacuum from.

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Old 05-14-2010, 03:40 PM
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Old 05-14-2010, 03:44 PM
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Old 05-14-2010, 03:45 PM
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Old 05-14-2010, 03:46 PM
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Old 05-14-2010, 03:48 PM
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Old 05-14-2010, 03:56 PM
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Old 05-14-2010, 04:16 PM
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Old 05-14-2010, 04:17 PM
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Old 05-14-2010, 05:07 PM
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Pretty much looks like mine, with the exception of all that emissions nonsense. Removed mine a very long time ago. Carter 1bbl carb. Your air-cleaner is very different than mine. I have ported and non-ported vacuum to the pvc valve. Engine vacuum from the vacuum manifold at the carb to a plastic manifold on the firewall and from there to the check-valve for the HVAC system inside. Also off the engine vac manifold to the brake booster. The other vac source is from my air-cleaner and that is only for the thermac system at the air-intake heat valve. No other vac is used anymore. Nope not even at the distributor...mech advance only. I tried to put an album up, but usually forget the 'how to' and mess something up.
https://www.ford-trucks.com/forums/members/parr4-8204-albums.htm
 
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Old 05-14-2010, 05:19 PM
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Does yours have a vacuum resivoir? Mine doesn't look like it ever had one. This truck is odd, because it was manufactured in Canada.

When you said pvc valve did you mean pcv valve?

By vacuum manifold are you reffering to the metal bar with the fittings on it located on the pass side underneath the carb?

Mine has two electrical conectors that are currently unused over on the pass side, are yours hooked to anything?

Do you know what is supposed to go on the fitting at the top of the carb that curently is capped with the red vac cap?
 
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Old 05-14-2010, 05:42 PM
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Yes vac reservoir. Vac feed hose to it comes of the 3-inlet plastic check valve for the HVAC.
Your red-cap on the upper part of the carb is a heat-stove for the carb. You can see it on one of my album photos.
Yes, engine manifold vac is the metal fitting below the carb...also pictured on album.
One of the electrical connectors is for the electric choke. I disabled my choke. The other connector is prolly for the idle-speed 'kicker' used to increase the idle about 100rpm when the AC compressor is On.
Yes PCV valve
 
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Old 05-14-2010, 05:57 PM
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Thanks, i'm sorry about blasting you with a bunch of questions, but I need her to take on daily driving duties this monday.

I can see the heat-stove connection in your pics, but can't tell where the other end goes. I don't see an obvious place for it on mine.

Are you using the idle speed kicker on yours? Is it suposed to be connected to the + trigger for the AC clutch? Thanks a bunch for helping me out, I really appreciate it.
 


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