Vacuum leak
 

What is the procedure for checking for a vacuum leak on an 8ba?


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Re: Vacuum leak
 

Get a can of engine starting fluid. It contains volatile and easily flammable chemicals such as heptane and diethyl ether. With the engine idling slow, spray small bursts of it around throttle shafts, carburetor base, intake manifold mounting gasket edges, vacuum hose fittings, etc. If for any of those bursts the engine idle momentarily increases, you have found a vacuum leak at that spot.

Re: Vacuum leak
 

I was checking for vacuum leaks with starting fluid as you describe. I did a “test of the test” by spraying a little into throat of carburetor. Very small squirt. Didn’t increase RPMs as expected. Bogged down! RPMs dropped. Why?

Re: Vacuum leak
 

If you spray over a vacuum leak you are adding fuel to a lean mixture caused by the leak. If you spray fuel into a mixture that isn't leaned out by a leak, you make the mixture over rich.

Re: Vacuum leak
 

That makes sense. Thanks. Sometimes I miss the obvious.

Re: Vacuum leak
 

If you use starting fluid. Unhook the fan belt and do it outside with a Fire extinguisher handy.


There's a very inexpensive, safe way of doing it also. Go on Youtube and search "smoke test DIY vacuum leak tester". Make one for $15.00



Works Great! Just block off your exhaust and carbs. I used the cheap disposable gloves and rubber bands. Don't cut corners and not epoxy the soldering iron and hoses in the lid.

Re: Vacuum leak
 

Although I never tried it , I saw propane can also be used.

Re: Vacuum leak
 

I tried the propane it failed to show me where the crack in the intake was. The smoke test pinpointed the spot. Just remember to exhale into the tube not inhale .Ha Ha.

Re: Vacuum leak
 

Be careful about using starting fluid, in any case. The main component is usually ether, and is highly combustible, and explosive.