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Vacuum Line Help


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Hey All,


I'm having some idling issues that I think are related to misplaced hoses, plus a bonus throttle stuck occurrence. I recently picked up a '78 Manual 620. The seller previously had a weber carb in place, but swapped it back to original carb/manifold for sell. 


Once I received the the truck, the engine would die after initial start up unless I rev'd the engine for a few minutes and then it would run fine. I popped the hood & at first look I found a hose that went to nowhere, realized it had a vacuum, placed some electrical tape over the hose & the truck started up no problem. Fast forward a little later, I'm driving the truck & the throttle is stuck. The pedal moves freely & I am able to clutch out into neutral but the engine was going as if I'm slamming on the gas. I turn off the truck, press the pedal a couple of times & it seemingly resets to "normal". 


I make it home & now I'm on a mission to correct these hoses to fix idling & hopefully fix this throttle thing (or find out what the hell happened). 


The red circle is the hose that has suction & I taped, No idea what purpose it serves.

The green I believe is the Anti Backfire Valve, & i think it's supposed to connect to the Manifold circled in pink.

The yellow circle stuff I think is the altitude compensators? the didn't have hoses at all...





Any help will be much appreciated. Thank you for your time.


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RED connects to the underside of the air filter and is the vacuum source for the ATC (air temp control) Unplugged, it's a vacuum leak and won't idle well if at all.


GREEN also goes to the air filter to draw filtered air into the anti backfire valve. Looks like a hose elbow is missing.


Throttle cable should only be a foot long. That is off something else and has a major KINK in it. Try to position it so the bends are wider.

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PINK goes to anti backfire


Yellow (top pair).... one goes to the charcoal canister. I can see that the hose is missing on the canister end in the top picture so for now seal it with tape. The other goes to the intake hose circled in RED


Yellow (bottom pair) Can you show the inside of the air filter????

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The rubber hose under the Yellow line connects to the fitting on the round thing on the end of the air filter snorkel pictured below.




The black object at about 4 o'clock is the temperature sensor that operates the ATC (auto temp control) in the snorkel.


At about 5 or 6 o'clock is the altitude compensator. As elevation increases the fuel air mixture becomes richer so this sensor opens an air bleed into the intake to lean it out. I have no idea why it would be on a vehicle in Texas. Is it from out of state? Look under the air filter on the  two missing hoses.  


At 10 o'clock is the idle compensator. Under extreme hot idle conditions, the idle mixture becomes too rich. This device bleeds air into the intake to lean it out.

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