shane1 Posted March 14, 2009 Report Share Posted March 14, 2009 First i am working on the pic kinda stupid with computers but iam haveing a problem with the 84 its idleing about 3000 rpm or more i have sprayied the intake and carb looking for a vacum leak and cant find one have know idea where to go from here plz help and ill try to get the pic as soon as i can promise ill get the wife to help she'll know how Quote Link to comment
ezcruiser Posted March 15, 2009 Report Share Posted March 15, 2009 You can do a smoke test with a wet rag, duct tape, small hose and a cigar. Look and feel for old hoses, if you have had the intake manifold off go back and retorque the bolts make sure there's nothing pushing up on the manifold or putting it in a bind. Make sure you have a nice flush fit against the head before you tighten down the bolts. If it's a bad leak you should be able to hear it hissing, so poke your head around the engine bay. Would the truck happen to be blowing a white smoke now out the exhaust? Quote Link to comment
datzenmike Posted March 15, 2009 Report Share Posted March 15, 2009 Is the choke off? By this I mean is the choke plate vertical like this: http://i138.photobucket.com/albums/q251/datzenmike/720%20stuff/carb720shouldlooklikethisLarge.jpg[/img]"] Is the throttle fully off and the throttle plate closed or is the fast idle cam stuck on fast idle. Quote Link to comment
shane1 Posted March 15, 2009 Author Report Share Posted March 15, 2009 Havent had the intake off and have checked the hoses and fix a few that were cracked. Cant hear a hiss and when sprayed carb cleaner there wasnt a change in the motor. So i dont think that theirs a leak. the choke is open but i have no idea where the fast idle cam is. I have another carb on the 83 i have but honestly the carb look kinda hard to take off with the bolts under the bowl and stuff searched the site for a post on takeing it off but seem that 720's arent that popular . and thank you for takeing the time to help Quote Link to comment
shane1 Posted March 15, 2009 Author Report Share Posted March 15, 2009 Well changed the carb from the 83 to the 84 and still no change still idles really high i guess next is the intake. any suggestions? kinda lost at this point really want to get her going Quote Link to comment
datzenmike Posted March 15, 2009 Report Share Posted March 15, 2009 (edited) A vacuum leak would not give a high idle. Air that gets into the intake would only dilute the gas/air mixture and lower the vacuum resulting in a poor idle. If choke is off, the fast idle cam may be stuck. Here is the fast idle cam, note the bottom has steps to give less and less fast idle as the choke slowly opens as the motor warms up: Here is the cam with the fast idle screw on one of the steps : With the choke held open and the throttle partially open, this plastic cam should be free to fall of it's own weight down out of the way. Use carb spray or WD-40 and spray this area and work all the linkages to loosen and clean all parts. The secondary may be stuck slightly open. Had this happen to me. Very high idle could not figure it out. One day I reached around behind and lifted the rod connecting the secondary to the vacuum diaphragm that operates it. When I lifted it it revved up and when I let go it seated properly and the idle dropped to about 500RPM. I had to adjust the idle up because I had turned it down so far. Funny thing is I later found a picture of the carb while rebuilding/adjusting and you can clearly see that the secondary isn't closed tight. __________________ Edited March 15, 2009 by datzenmike Quote Link to comment
shane1 Posted March 16, 2009 Author Report Share Posted March 16, 2009 i will check that tonight since its laying in the 83 but that would be my luck that its 2 carb with the same problem thanks for the help guys Quote Link to comment
shane1 Posted March 21, 2009 Author Report Share Posted March 21, 2009 Well found a piece of plastic holding the secondary open so guess the 250 for the 84 and the 83 wasnt to bad after all Quote Link to comment
datzenmike Posted March 21, 2009 Report Share Posted March 21, 2009 The secondary may be stuck slightly open. Had this happen to me. Very high idle could not figure it out. One day I reached around behind and lifted the rod connecting the secondary to the vacuum diaphragm that operates it. When I lifted it it revved up and when I let go it seated properly and the idle dropped to about 500RPM. I had to adjust the idle up because I had turned it down so far. Funny thing is I later found a picture of the carb while rebuilding/adjusting and you can clearly see that the secondary isn't closed tight. __________________ Gotta love easy fixes the PO didn't figure out. Good score. Quote Link to comment
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