2F Backwards world... Only idles WITH a vacuum leak (1 Viewer)

[island45]

Ran and idled perfectly. ran for some beer tonight and when I got to the place it wouldn't idle. Had the perfect rythmetic idle til now. Got home, and started playing, choke pulled about a quarter, idle OK but nort symphonic. Disconected hose to carb, got better... I have a brass petcock valve in one of the intake manifold holes(desmogged). With that opened almost normal idle, but a bit rough compared to what it was like.I turned the idle adjustment screw in and it got better. Even closed was OK. Backed it out one turn. Why would it suddenly run better with a pretty bic vacuum leak. Oh, and I pulled the PCV hose out the the valve connected and it had good suction at the ball end of the PCV valve. ????

 

[island45]

OK, so I'm gonna 'answer' my own thread... It's 11;30 at night here... My wife is on the mainland for 3 days, so I just had to investigate.... Turns out it's running on four cylinders. 5 and 6 made no difference when spark plug leads were removed... 5 and 6 plugs wet and sooty, not gray/brown. Soooooo , that brings us to a head gasket. Neighboring cylinders both out, a gap in the gasket between the two. Bummed... Head gasket not fun. Ok it was still just 9:30 at night, animals fed, all 10 chickens locked up, so I do a compression test on the trusty 2f . 195,000 miles, have owned it for something like 36 years now, head NEVER off. When I first brought it back from the dead after sitting in the dank woods for 20 years the compression front to back was 155 144 148 151 152 150. With my diagnosed head gasket failure tonight I decided to survey the damage..... But wait, with the same compression tester, and driving it fairly hard for 3 months and about a thousand miles, the new readings are as stated here: and I swear on my mother's grave..... 168 168 170 169 159 170...... SOOOO I guess it must be electrical, like the cap has a carbon arc from 5 to 6... OR in the last 3 days a mud dauber has built a nest in that branch of the intake manifold , unlikely with a pleated air filter....

 

[whitey45]

Sounds like fouled plugs due to too much gas. If it runs better with a vacuum leak, you are dumping alot of fuel. Float level ok, needle and seat not sealing?

 

[4Cruisers]

What distributor are you running? The original extra small cap distributor?

 

[island45]

engine is a 79 2f. I am running an SOR non USA dizzy I bought in the mid 90s. I have a couple of new NGKs I will see what happens, and also check float level. Thank you for the needed input.

 

[island45]

Whitey45 wins this round! Thanks! Float needle hung up. I gave it some pretty good love taps. Had to shut the brass petcock and it's back to idling smooth as silk. I have added a hefty dose of marvel mystery oil to the gas and that has solved problems of this nature for me before. And as far as compression goes I am pleasantly surprised at thos numbers. The previous 20,000 miles were put on it by my ex who grabbed it in the divorce. I was able to trade it away from my son after she gave him the title. It still had my date and miles written with a sharpie on the oil filter when I got it back. Just shy of 20,000 with no oil change. A 2f is an incredible engine.