Fresh bottom end, rebuilt head, HG, carb rebuild, intake gasket. Replaced dizzy with a FJ60 large cap type, did not help. It only pulls 12lbs of steady vacuume. Been all over it with either, no vac leaks. Idles smooth when cold, wont idle when warm, then if you hold it at like 1000rpm's, it revs up to like 2000 then back by its self constantly? WTF I am tired and stumped. Ideas? Thanks!
2f revs uuuup and dooown by its self if held steady at 1000rpm's
- Thread starter motoloco
- Start date
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carb checks
Make sure the check valve in your PCV is working and not just wide open all the time
is the choke okay?
junk in the fuel inlet?
turn your idle adjustment screw all the way in and see if it still runs--if it does it is not getting fuel from the idle circuit
check vacuum hoses for leaks, carb base etc
can you hear the carb solenoid click when you turn the key on
Thermostat stuck wide open?
Make sure the check valve in your PCV is working and not just wide open all the time
is the choke okay?
junk in the fuel inlet?
turn your idle adjustment screw all the way in and see if it still runs--if it does it is not getting fuel from the idle circuit
check vacuum hoses for leaks, carb base etc
can you hear the carb solenoid click when you turn the key on
Thermostat stuck wide open?
solenoid
You should be able to run a jumper from the battery for power as well or just use a test light and then run the new ground like pinhead pointed out
also read this
http://www.fordf150.net/howto/diagnoseengine.php
You should be able to run a jumper from the battery for power as well or just use a test light and then run the new ground like pinhead pointed out
also read this
http://www.fordf150.net/howto/diagnoseengine.php
Last edited:
- Thread starter
- #6
The fuel cut selenoid is getting pwr, will check constant ground. Air idle screw will shut the engine down, so it is running on the idle circut (when it will idle). The 12lbs of vac. should be 16-17 so that indicates a vac leak BUT, it is pretty consistant which is unusual for a vac leak. Thought about a cracked manifold from the heat riser, but it does not smell extremely noxious like it usually would with exhaust making its way into the intake. I capped the PCV, no change. Going to pull the carb and intake back off. Thanks for the good ideas!
Actually, vacuum should be in inches of Mercury ("Hg), not lbs... that's what made me laugh...
Do you have an aftermarket cam? They run lower vac at idle...but not down to 12.
Do you have a brake booster? They can leak vacuum.
Once upon a time, I bought a brand-new carb from the dealer, and got a vacuum leak with it that I could not figger out. Seems the factory forgot a plug in one of the carb passages.
- Thread starter
- #8
Sorry, I mean HG's. The brake booster is where I have been hooking my vac. guage. I am putting on a different carb here in a few to see if that is the culprit. Its funny you just chimmed in about a carb vacuume leak, I was having a conversation with a buddy at the same time, If a possible carb issue could cause LOW vac. Thanks for your input. Hopefully I will have a positive update here soon.
